H-I0126

FOR ·'AIRCRAFT

FASTENERS

IIIICDONNELL DOUGLAS

-~--.----------~-.-------------.~-.-----------.---.--.-~--~- " _ ... _ . . _- -----_._------ . , _··----------·- l i)'

© Copyright, McDonnell Douglas Corp., 1987

UNPUBLISHED

Written and Compiled by C. H. Cook, Cl-280 Quality Assurance

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NOTICE

McDonnell Douglas Corporation proprietary rights are included in the information disclosed herein. Recipient by accepting this docu­ment agrees that neither this document nor the information disclosed herein nor any part thereof shall be reproduced or transferred to other documents or used or disclosed to others for manufacturing or for any other purpose except as specifically authorized in writing by McDonnell Douglas Corporation. Unpublished - created on prepara­tion date of this document. All rights reserved under the copyright

. laws by McDonnell Douglas Corporation.

The information in this document is subject to design and developmental changes without notice. Since issuance of this docu­ment is unofficial and distribution uncontrolled, accuracy, currency, or completeness of the information is not assured. Reference must be made to latest revised, officially issued documents for authoritative information.

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PREFACE

Air transportation is expected to continue to expand in the years

ahead. Douglas aircraft flying the skies of today will serve as spring­

boards to the aircraft of tomorrow, much as the DC-3 and DC-61ed the

way to the DC-8, DC-9, and MD-80, and the DC-IO to the MD-ll. The

technical knowledge acquired from these airplanes will be incorpor­

ated into the design and manufacturing processes of the future.

This process of evolution is evident in fasteners and hole preparation.

Today, there are numerous. types of fasteners, made from different

metal alloys; many are more intricate in design than those of the past.

Selection of fasteners is more complex since specific functions often

limit usage. This has created a need for engineers who specialize in

fastener technology. Hole tolerances have become progressively

smaller for a larger percentage of holes. It is futile to purchase expen­

sive fasteners and install them in oversize holes.

Thousands of hours of assembly time are spent each working day in

drilling, reaming, burring, and countersinking thousands and

thousands of holes. A large number of fuel tank and fuselage pressuri­

zation leaks have been traced to substandard holes. Hole preparation

that meets all specifications is perhaps the most important function

and responsibility of an aircraft assembler. It is the key to leakproof

fastener installations, strength requirements, and a long useful flying

life.

Aircraft safety, reliability, warranties, and customer satisfaction

require that Quality Assurance and Manufacturing personnel become

more technically oriented. Integrity of tooay's aircraft structure

would be impaired by the hammer-type mechanic of the past. Aircraft

of the immediate future will create the need for structure assemblers

to develop their skill to a degree that is more comparable to the preci-

sion, machine-shop type mechanic.

Proficient employees have a background of knowledge and therefore

quickly recognize when the work is not progressing satisfactorily.

Less experienced employees are not cognizant of the discrepancy and

its implications; therefore, the same repetitious errors may occur.

The competitive elemeilt makes it doubtful if .any organization could

:longsurvive if it ,ever became satisfied with minimal job 'competence.

An executive of ;a large firm said it less subtly: "We either grow (in

competence) or we go."

If the past is a criterion of the future, it seems reaSonable that we

must be more vigilant ;and be more willing to expend 'effort,con­

stantlyand persistently, tou;pgrade Q1ll'competence. Personal goals

as well as otg;aniz:ational ,objectives should be unequivocally stated:

"'To become adept ,and proficient in ali phases of hole preparation."

The rewards for achieving such a ,goal, both individually and 'collect­

ively, will ensure '''success today.and tomorrow."

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CONTENTS

Section

1 Introduction ............................... .

2 Structural Factors .......................... .

3 Hole Tolerances ........ ... ................. . 4 Hole-Cutting Tools .......................... . 5 Edge Distance for Rivets ..................... .

6 Fastener Spacing ........................... .

7 Hole Drilling Practices and Techniques .......... . 8 Checking of Hole Sizes ....................... .

9 DeburringofHoles .......................... . 10 Alignment of Parts .......................... .

11 Drawing Symbols for Fasteners ................ . 12 Countersinking ............................. . 13 Dimpling ................. : ................ .

14 RivetOrientation ........................... . 15 Method Drawing S5076260 ................... . 16 BreakingHoleEdges ........................ .

17 Adjustable Stop Countersink Holders ........... . 18 Countersink Cutters ................. . ....... .

19 Stop Countersink Adjustment and Use .......... . 20 Spot Facing ............ .. ................. . 21 Coining ............ .. ..................... .

22 Hole Expansion ............................ . 23 Glossary .................................. .

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1-1. SCOPE

SECTION 1 INTRODUCTION

This manual has been prepared by Quality Assurance primarily for

the use of inspection personnel, but may be used by other McDonnell

Douglas personnel, as required, for training and indoctrination.

Procedures commonly used to drill, ream, burr, countersink, dimple,

and coin aircraft structures to ensure proper holes for fastener in- I stallations are described in this manual. Technical guidelines, shop I .

practices, and other techniques have been included to aid the user in

producing the finest aircraft in the world.

NOTE

Assembly procedures and specifications contained in this

manual are for reference only and may be changed without

notice. This manual is for advisory purposes and shall not be

cited to accept or reject work nor is it intended to dictate shop

practices.

Some portions of this manual do not relate specifically to detection of

discrepancies, but are presented to gain insight into the parallel pre­

vention function. Proficiency in conducting surveillance audits of

work in progress requires detail knowledge of tool use and assembly

procedures. The manual also supplements the conventional after-the-

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work inspection by familiarizing personnel with documented

specifications.

1-2. ARRANGEMENT

The manual is organized so that classroom discussion may be limited

. to specific topics. The text has been arranged in 22 sections, with each

section broken down into various subjects. illustrations and tables

have been provided to help make text material more clear. A table of

contents lists, in sequence, all section titles. An alphabetized glossary

at the back of the manual explains various terms used throughout the

text.

1-3. SPECIFICATIONS AND RELATED DOCUMENTS

The following specifications and documents will assist the reader in

understanding and following the techniques and procedures outlined

in this manual:

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Douglas Process Standards

Douglas Drafting Manual

Douglas Quality Specifications

AN, NAS, and MS Standards

Rivet and Screw Hole Preparation, Method Drawing S5076260

1-2

2-1. GENERAL

SECTION 2

STRUCTURAL FACTORS

Today's aircraft (Figure 1) operate most efficiently at altitudes of

30,000 to 40,000 feet. Man cannot survive in this rarefied air without

supplemental aid. This aid is furnished by maintaining the cabin as

near to sea level pressure as possible at all altitudes.

The limiting factors in cabin pressurization are the structural

strength of the airframe, the leakage rate of the structure, and the

capacity of the pressurization components.

In the MD-ll, a sea level cabin pressure can be maintained up to a

flight altitude of 22,400 feet. A cabin altitude about equal to a

7,600-foot mountain can be maintained at a flight altitude of 43,000

feet. At these altitudes, there is a difference in pressure of 8.6 pounds

per square inch'between the air inside the cabin and the air outside.

Approximately 1,240 pounds of pressure are applied to each square

foot at the boundary of the pressurized area; thus, the application of

force on just one fuselage panel amounts to many tons.

Three air conditioning packs pump air into the pressurized areas of

the fuselage. In the MD-ll, the volume of air flowing into the cabin is

from 2,500 to 5,500 cubic feet per minute, depending upon the cabin

configuration. Therefore, it is mandatory that the tens of thousands

2·1

MD-11 - A HIGH-TECHNOLOGY TRIJET FOR COMMERCIAL AIRLINE SERVICE, WITH BASIC TWO-CLASS SEATING WILL CARRY 276 to 405 PASSENGERS UP TO 6,800 NAUTICAL MILES. PROVIDES UNIQUE FLEXIBILITY IN RECONFIGURING THE INTERIOR CABIN .

DC-10 - FOUR VERSIONS PROVIDE ECONOMICAL OPERATION ON ROUTE SEGMENTS FROM 300 MILES TO MORE THAN 6,000 MILES. CAN CARRY 255 TO 380 PASSENGERS. CONVERTIBLE FREIGHTER AND ALL­FREIGHTER VERSIONS ALSO AVAILABLE.

KC-10 - AN AERIAL REFUELING TANKER CONVERTIBLE TO ALL CARGO OR TO MIXED PERSONNEL AND CARGO. RATED " OUTSTANDING" BY THE USAF FOR EXCEEDING RELIABILITY AND MISSION CAPABILTIY GOALS.

MD-80 - FUEL EFFICIENT, QUIET, AND RELIABLE. THE BASIC MODEL CARRIES A MAXIMUM OF 172 PASSENGERS OVER RANGES UP TO 2,000 MILES. OTHER MODELS OFFER EXTENDED RANGE, SMALLER SIZE FOR ROUTES WITH LESS TRAFFIC, AND ADVANCED-TECHNOLOGY FLIGHT GUIDANCE.

CO .............. m ............... ~O .. ~ C-17 - THE ONLY MILITARY AIRCRAFT DESIGNED TO TAKE THE ARMY 'S LARGEST TANK AS CARGO. POWERED

LIFT ALLOWS LANDING DISTANCES UNDER 3,000 FEET AT MAXIMUM LANDING WEIGHT. MAXIMUM

TAKEOFF GROSS weIGHT IS 57=J

G~: T-45 --:- PART OF A U.S. NAVY TRAINING SYSTEM THAT ALSO INCLUDES SIMULATORS AND LOGISTICS SUPPORT.

THE T-45A IS BASED ON THE DESIGN OF THE RAF HAWK, MODIFIED TO NAVY TRAINING NEEDS AND CARRIER OPERATIONS.

FIGURE 1. MCDONNELL DOUGLAS AIRCRAFT OF TODAY AND TOMORROW 2-2

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of fasteners installed at the outward boundary of this pressurized

area be airtight. However, pressurization checks allow for a very

small amount of leakage, since fresh air is continually being pumped

into the cabin interior during flight operations.

Integral wing fuel tanks have requirements similar to those pressur­

ized portions of the fuselage with one major exception: the tank struc­

ture must be leakproof instead of airtight. Safety requirements make

it mandatory that there be no fuel leakage whatsoever.

The fuel capacity of the MD-11 is more than 38,000 gallons. The

weight of the fuel ranges up to 259,000 pounds, almost 130 tons.

2-2. GUST LOADS

During flight, gust loads (the result of sudden up and down currents

of air) induce additional stress on the airplane, causing the wings to

flex up or down. The wingtips normally flex up 3.5 feet under normal

flight conditions. Should abnormal maneuver conditions be neces­

sary, the wings are designed to deflect as much as 11 feet.

The extremely heavy stresses on the wing can best be understood if it is kept in mind that the wings support the entire weight of the air­

plane. The maximum takeoff weight of the MD-11 is 602,500 pounds, .

and in certain flight attitudes the stress on the underside of the wing

may reach 13,500 pounds per square inch.

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-] The wing of such an aircraft is an engineering marvel when considera- J .

tion is given to the weight ratio, aerodynamic functions, and fuel

carrying capacity.

2-3. FATIGUE LIFE

McDonnell Douglas commercial airplanes are designed for a long and

useful flying life. Long fatigue life Oife expectancy of parts and

assemblies) depends on superior design and quality workmanship.

One without the other means a shorter service life. Generally speak-

ing, fatigue of metal is caused by alternating tension loads, although

there are also many manufacturing processes that may reduce the

fatigue life.

2-4. ENGINEERING SPECIFICATIONS

Engineering is responsible for providing the specifications that pro­

duction personnel need to manufacture a quality product and ensure

that it meets contractual obligations.

However, the' 'why" for a certain requirement is seldom explained. It appears to be unreasonable to expect this type of response.

Engineering has the knowledge, the experience, and the facilities to conduct thousands of tests. Tests are continually being accomplished

to evaluate strength factors, material requirements, and manufactur­

ing processes.

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For example, the graph shown in Figure 2 illustrates the conclusion of

a laboratory test for drilling titanium. Improper drilling reduced the

designed fatigue more than 80 percent.

6AI-4V TITANIUM

DRILLED WITH HOT, DULL DRILL

DRILLED PER DPS 3.67-22

, NUMBER OF CYCLES TO FAILURE

FIGURE 2. IMPROPER DRILLING

2-5. STRUCTURAL INTEGRITY

The adage "Quality cannot be inspected into a product, it must be

built in" is still true. Structural integrity is directly related to each

employee's integrity and willingness to become involved with the

multitude of small but "make or break" details of individual job

. assignments.

2-5

3-1. GENERAL

SECTION 3

HOLE TOLERANCES

Engineering chooses hole diameters with as large a tolerance as

strength, fatigue, and function requirements will permit. The reason

for this is that a considerable cost savings accompanies any increase

in hole tolerance. An aircraft assembler's job, therefore, is to produce

a hole size that is within engineering specifications. Quality is not nec­

essarily a gage of precision; it refers to accuracy that is within

specifications.

Any dimension called out by Engineering is the desired or perfect

size, which may be possible but highly improbable. Therefore, all

dimensions have a permissible variation. One criterion for establish­

ing hole sizes and tolerances is the fastener diameter and its allowable

variation. A hole may be drilled to the minimum size and a fastener

may be of the maximum diameter. On the other hand, a maximum size

hole and a minimum size fastener will provide a fit of greater

clearance. Either fit is of acceptable quality providing the tolerances

of both the hole and the fastener are within the specified tolerances.

Hole tolerances must be maintained to ensure that shear stresses are

distributed evenly; then, each fastener can carry its proportionate

share of the workload. Fasteners installed in oversize or elongated

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holes will transfer shear loads to proper sized holes nearby. In effect,

this reduces the number of fasteners installed. (See Figure 3.)

TENSION STRESS

t .-

SHEAR STRESS J OR WORK LOAD

TENSION STRESS

FIGURE 3. SHEAR AND TENSION STRESSES

OVERSIZE HOLE

SHEAR STRESS

GAP (EXAGGERATED FOR CLARITY)

Fastener hole-filling characteristics are not always the same in over­

size and elongated holes, and may cause premature fatigue failures

and leaks of fuel or air in sealed areas.

The most important assembly function is not just the installation of

the fastener - it is the hole preparation as well. It usually requires

more knowledge and skill to produce a quality hole. Great reliance is

placed upon the integrity of the mechanic, since this phase of the

operation cannot be seen or inspected on a completed assembly. Relia­

bility and safety of the airplane are directly related to this operation.

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3-2. FITS FOR BOLTED CONNECTIONS

Hole sizes for bolted connections are shown in Table 1, which provides

for six classes of fits. Notice that six different hole sizes are called out

for 1I4-inch bolts or screws. These different classes of fits serve as a

guide for Design Engineering in meeting strength and inter­

changeability requirements and for facilitating production.

TABLE 1 EXCERPT FROM ENGINEERING DESIGN HANDBOOK: HOLE SIZES FOR

BOLTED CONNECTIONS

~ -- -- --GOI(RAl 1/ ClASS 1 ' I"" CLASS II "" ClOse ~lASS In I CU.~SIV .. ' I CUSS V ... CUSS VI '\ PURPOse

1\J111 oV£JIso .. A \.1/32 OVERSIii TOLERAICCE

'- Cl.OIE FIT / '- 7 IOLT 01.1. BOLT OIA EXIIIA CLOSE FIT AND I..U" TS

USE FOil T(tISIOtiI "nACKM(ans 'il1T" ,l.NO LIMITS USE ro ttMEMT USE r 01 to (lAS 618)

MEGLIGI eLE SHUt! OR ",HCRE .lSSEJlt8LT (US 618) SU8JECT TO REVEISING LOADS. MI NIMIZ£ loostlll£$S II JOlllS. TOl(RUICES ARC ADvERSE.

CONTOURED $UR- G(leUA!.. BRACJ:(T MUlTi - SOLT PAT- COiEan SHEAR PRACTICULE PRECtSION FleES ,KOlts 1111 .-..0 £Qu I PMUT TUNS WHERE 1.- APPL.ICATIONS £x- LIMITS wHiCH CAli TOOUNG "'0 OR MORE A TfACH"4[NT Ex- T£RCICAICGUBI 1..1 TY CCPT AS NOTCO 8f: OBTAINEO 8T REOUlREO. PU,NES. aRIOGING CCPT AS NOTlO rOR CLASS HI. REAMING OR S£\I£RAL PU-TS. fOR CLASS 1. OR A "ATCH 'NG. EQUIVALENT OM ONE PUT IS HOLE PA TTEb IS A~EM81". THttlO[O OR REQU i RED •••• COUNT(RSUNII:. ETC.

S'ZE It"ITS L ~~r~sl CLf~:;)C[ HOLE CLEUANCE

SIZE t~~!)! HOLE CLEARANCE L~~r~$ fLf~~~}C MOLE ClOIAllCE HOlf CUAtUCE (01A) LIMITS (REF) L'.ITS (REF) LIMITS (REF) LIMITS (REF) .. .16 .!. .u,O

. 18 :::i .152

I., .19 i: .166 .20 .180

." ~o .19) .. .23 !5~ .208

. 1895 .,. zc .0565 .218 .0285 "0

.1895 . 199 • .JC95 .190 .0005 . 1195 .0000 . 1895 . 0000 no ~" .1870 .26 Ow .07)0 .229 .01l20 .1885 .,02 .,)!35 .19 .. . 005$ .1915 .00)0 . 1905 .0020

1 :~:;~ .)06 .0565 .219 .0295 1 .,..! .257 .0075 .250 . 0005 :mf . 0000 . 2.95 . 0000

• . )19 . 0720 . 291 .ouo • .2&8 .261 . 0125 .'50 .0055 . 00)0 .25OS .oozo

n .3120 . )68 .0560 .jl', .0)00 n .)110 ~') . 011 .,US ,0005 :mg .0000 ~ . 0000 .)095 .)82 . 0725 .J5' . Ou5 .J110 .327 .0 16 .)165 . 0055 .00)0 .0020

1 . )"5 .11)5 .0605 .110& . 0 295 i -.3 1115 .) .. .0115 .)'~ . 0005 .3ns .0000 .,ns . 0000

• 3120 .'50 .0820 .416 . 011.10 .37)5 . )90 .0165 .,79 .0055 .)765 .00)0

lfv~ .0 )00 7 .11)70 ,~5J . 016 .1l;H5 . 0005 •• )70 ~ 16 .14)60 • .u57 .021 ."25 . 0065 . 090

..... .40995 . ~16 .~~~5 . ~~~ .~~~5 .........

3-3

3-3. CLEARANCE FITS

The selection of a clearance fit for a bolted connection is based on the

largest clearance (maximum looseness) between the hole and the bolt

that will meet shear requirements. Clearance fit holes are usually

specified for lockbolts and Hi-Loks when one or more members are

steel, stainless steel, or titanium. The protective coating of noncor­

rosive cadmium plating on the fastener is softer than any of the

materials listed above. An interference fit hole in steel or titanium

peels the cadmium plating from the fastener. The hole does not

expand, as with aluminum alloys, and the harder metals act as a die

(see Figure 4).

The peeled plating and particles of steel from the fastener are

deposited either between the faying surface or under the fastener

head. This creates a gap and may produce fretting corrosion. In addi­

tion to the gap, corrosion of the fastener is accelerated; therefore,

holes through steel or titanium are of close tolerance and are a clear­

ance or net fit. (An exception: See DPS 3.67-20 and -39 for unplated

titanium alloy or unplated corrosion-resistant steellockbolts and Hi­

Loks.) The entire shank (not the threaded end) of some special bolts

installed into interference fit holes may be coated with an approved

lubricant (reference DPS 2.70-2).

3·4

ALUMINUM ALLOY TITANIUM ALLOY

1. CAOMIUM PLATING PEELED FROM THE FASTENER

THE ABOVE PHOTO SHOWS THE RESULTS WHEN INTERFERENCE FIT HOLES ARE DRILLED IN TITANIUM (OR STEEL). THE TWO PLATES ARE SHOWN SEPARATED AFTER PLATED (CORROSION-PROTECTED) FASTENERS WERE FORCED INTO THE HOLES.

FIGURE4. RESULTS OF INTERFERENCE FIT HOLES IN HARD METALS - NOT ACCEPTABLE

3-4. INTERFERENCE FITS

Engineering considers the minimum fastener diameter when estab­

lishing the maximum hole size for an interference fit. A lockbolt

installed through aluminum parts is a good example. The specified

hole size is from 0.000 to 0.003 inch smaller than the minimum fas­

tener diameter. As the pin is pulled into the hole by the installation

gun, the hole expands to accommodate the lockbolt. The fastener is

designed so that the wall surface of the hole is not damaged or

_broached. In addition to a high-shear joint with a long fatigue life, a

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metal-to-metal seal is obtained that is leakproof Without the aid of

cheIllical sealants.

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Figure 5'shows the results of an engineering laboratory fatigue test

when close"tolerance holes were oversized.

SPECIFIED HOLE TOLERANCE - 0.001

NUMBER OF CYCLES TO FAI~URE

-- HOLE WITHIN JOLERANCE '

........ 0,001 PVERSIZEHOLE

...... 0.002 OVERSIZE HOLE •.

. FIGURE 5. PREMATURE FATIGUE FAILURE

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4-1. RUNOUT

SECTION 4 HOLE-CUTTING TOOLS

Runout of hole-cutting tools refers to the amount of eccentricity (wob­

ble) at the cutting lip of a drill or reamer; the axis of the cutting lip is

off-center to the axis of the drill shank. (See Figure 6.)

Ideally, there should be no runout, but mechanically this is impossible.

The mechanic should be aware of the inherent runout tendencies of

hole-cutting tools and how to minimize the problem.

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\...--" FIGURE 6. DRILL RUNOUT

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Runout is affected by several factors in hole-cutting tools - drill lip

concentricity, lip angle, flute symmetry, and torsional rigidity. Rigid­

ity (stiffness) is lessened as the number of flutes, flute lengths, and

overall lengths are increased or as the size (diameter) is decreased.

The type, balance, and manufactured precision of the motor chuck

also affect runout.

The degree of sharpness and straightness of hole-cutting tools adds to

the problem of runout, as does the trueness of the motor spindle and

the condition of its bearings.

During the drilling operation, runout is affected by motor rigidity, the

rate of feed, and the type of material.

Runout can be lessened through proper storage, use, selection, and

care of tools, and also through the use of drilling aids.

4-2. CARE AND CONDITION

Sharp drills with the proper feed produce large chips of a uniform size

and small burrs on the far side. Dull drills produce powdery chips and

large burrs and increase the possibility of enlarged holes and excess­

ive heat induction into the materials. Dull drills used in automatic feed

equipment, such as the spacematic, can be detected by listening to the

motor. If it slows down and tends to labor, immediately check the con­

dition of the drill and the size of the hole.

4-2

When drilling and reaming clad aluminum alloys, heat tends to fuse

the clad material (nearly pure aluminum) to the margins and lands of

the drilling tool. Inspect core drills and reamers for this "clad

bUildup" since it causes oversize holes and scoring of hole walls.

Crooked or bent drills tend to creep on the material surface, causing

scratches. Motor vibration and the resulting oversize holes are

usually caused by such defects. An extreme safety hazard is also

created by bent (even slightly) extension drills. Therefore, 6- and

12-inch extension drills should be used with a drill guide (see Sec­

tion 7-6).

Reamers and broaches should never be thrown, dropped, or indis­

criminately stored. The tool finish, cutting edges, and trueness may

be adversely affeclefr.--Burrs or scored ridges on the shank end of the

hole cutting tools also adversely affect concentric chucking. Refer to

Paragraph 7-4 "Chuck Runout."

4-3. LENGTH

Twist drills, double margin drills, core drills, and reamers are avail­

able in several different lengths. Always use the shortest drill that

allows access with out motor chuck damage to the nearby structure.

The advantages are:

a. When in use, the compression force on the hole-cutting tool

causes it to bow; therefore, short drills improve torsional rigidity

4-3

(longitudinal stiffness) and minimize runout.

b. Tool cost is reduced.

c. The hazard of drill whipping and possible injury to the operator or

other personnel is reduced.

4-4. DRILL SELECTION BY TYPE

There are so many different drilling conditions affecting hole sizes

that only a general guide is practical for the selection of hole cutting

tools. For specific problems related to drilling, consult Perishable

Tool Liaison personnel or the Hole Preparation Manual (Tooling

C652-5076260-PDSI).

4-5. DRILL TYPES

a. Twist Drills (See Figure 7.)

Twist drills are available in three sets:

1. Number drills from 1 (0.2280 inch) to 80 (0.0135 inch)

2. Letter drills from A (0.2340 inch) to Z (0.4130 inch)

3. Fractional drills from 1164 (0.0156) inch increments to

. 1 (1.000) inch I Sizes are stamped on the shank, and drill gages are ~vailable at

f ,) the tool cribs for verification.

If the tolerance of the final hole size permits selection of optional

sizes, use the smallest size.

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....

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DRILL AXIS \

~ 6 SHAlli<~

JOBBER LENGTH

• TWIST DRILL. HIGH-SPEED STEEL. STRAIGHT SHANK • AVAILABLE IN JOBBERS LENGTH - 6 AND 12 INCHES

FIGURE 7. TWIST DRILL

Twist drills are generally used in assembly work for final hole

sizes having an overall tolerance of 0.006 inch or greater. If the

hole tolerance is less than 0.006 inch, carefully evaluate before

using this type of tool.

b. Special Twist Tools

1 . Nitride drills are used to drill thin titanium material.

2. Cobalt drills are used to drill very hard materials such as

stainless steel (180,000 psi) and for deep drilling of titanium.

Cobalt drills retain their sharpness for a longer time, cut

faster, and generate less heat.

3. Split point twist drills, 135-degree angle, should be used for

deep drilling of steel and titanium.

4. Hi-spiral drills may be used for predrilling of thick aluminum

alloys to facilitate chip removal.

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" I '--'-~-""'-~r--::-----------.. - .... - ------:--.. -.-... ---;::"7.-'-- .---.. --~-.---.-----~---_._,_~~~~: .... ---:-J .

c. Double Margin Drills

The double margin drill (Figure 8) functions as two drills in one.

The piloted end cuts a predrilled hole and the body portion pro­

duces the final hole size. It is a fast and efficient tool for drilling

holes having O.003-inch tolerance or greater in thin aluminum

alloys.

These drills · are recommended if the total thiclmess of the

material is more than the length of the piloted portion (first step).

They should not be used for drilling titanium or steel parts, since

. more heat is induced than by other drilling procedures. An excep­

tion to this is small-diameter holes of 118 inch or less.

. DIAMETER OF 1ST STEP]

DASH NO. INmeAnY' OF 00"' s~. 80. DY DIAMETER U TOLERANCE + .0005 - .0000

U IT/'\\~~~-t CUTTING EDGES

FIGURE 8. DOUBLE MARGIN DRILL

4-6

d. Core Drills, Piloted

Piloted core drills (Figure 9) are recommended for the following

uses:

1. Predrilling for piloted reamer.

2. Holes having a 0.003-inch tolerance in thick aluminum alloy

structure.

3. Step drilling to prevent high heat induction into steel and

titanium materials.

JBODY DIAMETER

TOLERANCE + 0.0005 -0.0000

SEE SMALL TOOLS REFERENCE MANUAL FOR SIZES ~

~ S PILOT SIZE

~ '~~ "----------""-.::......;=--- . I ~LOT - NO CUTIING

EDGE

FIGURE 9. PILOTED CORE DRILL

e. Reamer, Piloted

For holes having a tolerance of 0.002 inch or less, always use a

piloted reamer (Figure 10). The use of a piloted reamer requires a

three-step procedure:

1. Predrill with a twist drill. The hardness and thickness of the

material may require a pilot hole prior to the predrill step. The

4·7

fSODY DIAMETER

SEE SMALL TOOLS REFERENCE TOLE.RANC.E + 0.0002 MANUAL RJR DlAMETERSIZ': 7('" -0.0000

~C==-~t~~~~~: 2:? t

FIGURE 10. PILOTED REAMER

The size of the predrill must correlate with the pilot of the

core drill used in Step 2.

2. Enlarge the predrilled hole with a core drill. The pilot size

should be 0.001 to 0.0015 inch smaller than the predrilled

hole. The body size must correlate with the pilot size of the

reamer used in Step 3.

3. Ream the core-drilled hole. The pilot size of the reamer should

be about 0.001 inch less than the core-drilled hole. Body size is

determined by the minimum final hole size specified by the

blueprint or applicable fastener DPS.

Hole-cutting tools are also available for oversize salvage fasten­

ers. Pilot sizes are correlated to fit into the original (oversize ) hole

(see Section 4-4).

4-8

SECTION 5

EDGE DISTANCE FOR RIVETS

The following information is taken from the Engineering Design

Handbook (DH):

Rivet edge distance (design) for general structural applications is

determined as follows: 2 x diameter + 1116 (0.06) inch

1. This design edge distance should be exceeded where weight or

functional penalty is not incurred.

2. This design edge distance is subject to normal tolerances. Where

conditions permit other than normal tolerances, the acceptable

tolerance shall be noted with the edge distance dimension on the

body of the drawing or in the general notes, as follows:

Rivet edge distance = 2D + 1116 (0.06) inch for detail parts.

Rivet edge distance = 2D minimum acceptable on assembly.

Rivet edge distance = 2D from joggles and adjacent structure.

5-1

Use In

Castings

Nut plates in primary structure

Riveted plywood joints where full

strength is required

Nonmetallic moldings

NOTE

- ~.-... ---.. -.... -.-.. ----~--- --

Design Edge Distance

3 times rivet diameter

4 times rivet diameter

4 times rivet diameter

3 times rivet diameter

The DR is used only by Engineering and is included here for

reference only.

!

, \

I

I I !

SECTION 6

FASTENER SPACING

6-1. MINIMUM RIVET SPACING

The minimum single-row spacing should be held to four times the

rivet diameter for 5/32-inch diameter and under. A minimum spacing

of about 3-112 times the rivet diameter may be used for 3/16-inch

rivets and larger.

Where closer spacing is required, multiple rows of rivets are used.

6-2. ADJUSTMENT OF RIVET SPACING (Reference DPS 2.70-2)

During master layout operations (MLO), fastener spacing specified

by the engineering drawing ~ot always be achieved. Method 1 or 2

procedures shall be used as necessary to adjust the spacing when the

distance between the end fasteners is not divisible by the specified

spacing.

Method 1

The spacing of the rivets at the end of the run may be adjusted

between the noted on-center dimensions and four times the rivet

shank diameter (4D). Figure 11 shows a typical example, using a

1/8-inch-diameter rivet on a 5/8-inch on-center spacing.

6-1

MINIMUM DISTANCE = FOUR TIMES

--J ____ r-__ ~I-T-H-E-RIV+I--SH-A-NKbID-IA-M-IT;Er-~--· -+----r-ffl:r--I END RIVIT LIT

IF RIVIT SPACING SPECIFIED ON THE DRAWING " IJWS our AS SHOWN ABOVE, ADJUST AS SHOWN BELOW.

I FIGURE 11. RIVET SPACING - METHOD 1

Method 2

When the spacing specified on the engineering drawmg is equal to

or less than 4D, it will not be possible to adjust in accordance with

Method 1. Under these conditions, make the nominal on-center

spacing 1/32-inch greater or less than that specified on the engi­

neering drawing, except for fuel seal rivet patterns having a rivet

spacing less than 4D. Fuel seal patterns less than 4D may be

spaced ± 1164 inch to get the required adjustment. The adjust­

ments under this method apply to as many rivets at the end of the

run as necessary.

Rivet spacing adjusted either by Method 1 or Method 2 is acceptable

provided the difference in the number of rivets between the engineer­

ing drawing and the MLO is not more than plus or minus one rivet.

Engineering must approve any difference of more than one rivet.

6-2

I I

NOTE

The above conditions also apply to rivet patterns established

with the aid of tools.

6-3. ADJUSTMENT OF SPACING FOR BOLTS AND LOCKBOLTS (Reference DPS 2.70-2)

The nominal spacing of bolts and lockbolts can be plus or minus 1/32

inch of that specified on the engineering drawing. This applies to as

many bolts or lockbolts at the end ofthe run as necessary; however, in no case shall the specified quantity be changed without Engineering

approval.

6·3

SECTION 7

HOLE DRILLING PRACTICES AND TECHNIQUES

7-1. GENERAL

Most of the fasteners used today are manufactured to close tolerances

and are costly. However, the use of precision fasteners in itself does

not mean that engineering standards of safety, reliability, and long

fatigue life will be met. Fastener strength and hole-filling character­

istics are not consistent when fasteners are installed in oversize,

belled, elongated, double, mislocated, undersize, and nonperpen­

dicular holes.

The hole preparation procedure is further complicated by the many

different hole sizes and tolerances. For example, 1/4-inch-diameter

fasteners of various types require about 25 different hole sizes. Hole

tolerances for most steel fasteners range from 0.001 to 0.004 inch;

rivet hole tolerances are usually 0.005 inch.

There is often a tendency on the part of Inspection and Manufactur­

ing personnel, through everyday association, to forget the minute­

ness of permissible variations in close-tolerance holes. For example,

this piece of paper is approximatley 0.004 inch thick. In order to pro­

duce assembly (not machine shop) drilled holes with a maximum varia­

tion of only one-fourth this thickness (0.001 inch), the correct tools

and drilling aids must be used,under optimum conditions, by a compe­

tent mechanic.

7-1

Because of restricted accessiblity and peculiarities inherent in a par­

ticular assembly, it may not always be possible or practicable to use all

of the practices and techniques that are suggested herein. However,

one conclusion appears certain: complete utilization increases the

percentage of quality holes; omission of anyone increases the proba­

bility of discrepant holes.

7-2. CORRECT AIR MOTOR SPEED (Reference DPS 3.67-22)

The selection of the correct motor speed is governed by the type of

cutting tool being used, the hardness of materials, hole tolerances,

and the size of the cutting tools.

As the drill or reamer diameter increases, the RPM (revolutions per

minute) requirement decreases. The outside lip of a larger hole­

cutting tool is moving proportionately faster than a small-diameter

drill at the same RPM. Therefore, the speed or RPM must be reduced

as the hole cutting tool increases in size (see Table 2). This not only

prevents tool damage but also improves hole wall finish, enhances

assurance of hole tolerances, and tends to reduce the induction of

excessive heat into the material.

Reaming, countersinking, and counterboring operations also require

slower motors'than the 5,OOO-RPM air motors (see Figure 12).

Usually, but not always, the 2/700-RPM motor may be used. The

recommended RPM is one-third to one-half the drilling speed. The

feed should be two times that used for drilling.

7·2

TABLE 2 MAXIMUM RATED MOTOR SPINDLE SPEEDS (RPM)

TWIST DRILL DIAMETERS

UPTO UP TO UP TO UPTO MATERIAL 1/2 3/4 11/2

ALUMINUM AND MAGNESIUM ALLOYS' 1,500 1,200 1,000 750 500

ALL TYPES OF STEEL, TITANIUM, AND INCONEL. LUBRICANT REQUIRED" 2, 3. 300 250 200 150 100

DATA EXCERPTED FROM DPS 3.67·22

NOTES: USE DRILLING AIDS WHEN HAND·MOTOR·DRILLING HOLES: • LARGER THAN 114-INCH DIAMETER IN ALUMINUM • LARGER THAN 3/16-INCH DIAMETER IN STEEL AND TITANIUM ALLOYS

1. EXCEPTION: WHEN USING AUTOMATIC FEED AND SPEED DRILLING EQUIPMENT, THE SPEED MAY BE INCREASED UP TO 7,000 RPM. FOR HIGHER SPEEDS, SEE LIMITATIONS IN DPS 3.67-22.

2. OVER 180 KSI, CARBIDE DRILLS ARE RECOMMENDED. 3. SLOWER RPM MAY BE USED,

WITH CONVENTIONAL CHUCK. 2,700 TO 5,000 rpm.

FIGURE 12. AIR MOTORS

7-3

When drilling a joint containing dissimilar alloys, such as titanium,

Inconel, and aluminum, use the harder alloy in selecting the motor

speed. Do not drill steel, Inconel, and titanium parts with 2,700-RPM

motors. Laboratory tests show that structural fatigue life is severely

reduced.

Using C-clamps on air hoses to restrict the volume of air reduces both

the speed and power of the air motor. The motor stalls under a

workload and close-tolerance holes are belled or oversized. Finger

control (alternately depressing and releasing the motor trigger)

should also be avoided. This causes elongated holes and hardens the

surface of steel, Inconel, and titanium.

7-3. FEED RATE

Feed of a hole-cutting tool depends on the force applied to the drill

motor during the cutting operation. Machine shop feeds are figured in thousandths of an inch for each revolution of the drill and are com­

monly referred to as feed per revolution (FPR). Unfortunately, such

measurements cannot be used for hand motors used in assembly

departments. The proper rate of feed is acquired through experience

and by giving close attention to results. Some of the items that affect

feed rate are noted below:

a. Feed rate is limited by the motor speed and power. Motor power

should be sufficient to prevent the rate of feed from stalling the

motor.

7-4

b. Harder alloys require low feeds, while softer alloys may use a

higher rate of feed. Proper feed will produce chips· and spirals

rather than powder.

c. Different types of cutting tools require different feeds. The

number and length of flutes affect torsional rigidity (stiffness).

d. Too much feed will bow the cutting tool and cause runout. Long,

small-diameter drills require a slower rate of feed than short,

larger drills.

e. Use fast feed rates (without inducing runout), since fewer revolu­

tions of the motor are needed to penetrate the hole, and holes are

less likely to be enlarged. Longer cutting time increases the prob­

ability of a slight tilting of the cutting tool due to hand

unsteadiness.

7-4. CHUCK RUNOUT

The precision and accuracy of a motor chuck may be offset by the

method used in chucking a drill or reamer. Eccentric or off-center

chucking usually happens when only one chuck jaw is tightened. This

tends to move the cutting tool against the other two chuck jaws. This

is only a small amount, but it becomes increasingly more important as

the hole tolerances get smaller. Drill runout induced by chucking can

be minimized by tightening each chuck jaw uniformly until the drill is

completely tight. To make a quick comparison of the two methods,

chuck a 12-inch No. 40 extension drill in a high-speed motor. Use the

7·5

same drill for both methods and observe the runout. Be sure to take

precautions to control drill whipping. (See Figure 13.)

GRIP LIGHTLY AND AVOID CONTACT WITH FLUTES

FIGURE 13. FINGER CONTROL OF EXTENSION DRILL

The following are additional suggestions for reducing runout:

a. Never force a tool into an undersize chuck; this is a frequent cause

of damage to keyless or automatic chucks. It also causes scoring

and burring on the shank of the hole cutting tool.

b. Do not bottom the tool in the chuck; this may cause the tool to

bind. Allow about l/16-inch clearance between the shank end of

the tool and the bottom of the chuck.

c. Do not tighten if the drill flutes are within the chuck.

d. Never chuck over burrs on hole-cutting tools used for close­

tolerance holes since it contributes to drill runout.

7-6

7·5. DRILL NICKS

Drill nicks (Figure 14) on surrounding structure are caused by

excessive depth penetration of the drill. This can be eliminated by

using drill stops. (Figure 15)

FIGURE 14. DRILL NICKS - NOT ACCEPTABLE

FIGURE 15. USE OF DRILL STOP TO PREVENT DAMAGE

7-7

Always use a drill stop (see Figure 15) when drilling into assemblies

containing electrical or electronic equipment, fluid lines, insulation

bags, or inner structures. Adjust the drill stop to limit penetraton to

1/16 inch beyond the sheet. (Reference DPS 2.70-2).

7-6. DRILL SCRATCHES AND CHUCK MARKS

Drill marks not only detract from appearance, but also act as stress

risers that shorten the fatigue life of skins and structural members. It

is a mistake to believe that primer is the restorative cure-all for sur­

face damage.

Scratches and chuck marks usually occur when jobber length drills

are used and the grip of the hand near the motor chuck is improper.

Notice the proper grip for the left hand as shown in Figure 16. (Also

see Figure 17 for proper grip with the right hand.) Correctly placing

the thumb and forefinger on the skin surface will:

a. Provide stability in overcoming motor torque and preventing the

drill from spinning or walking away from the hole, causing

"pigtails. "

b. Give better control of drill point for accuracy in locating hole.

c. Prevent motor chuck from rotating on skin surface when drill

penetrates material.

When using extension drills, stabilize the drill runout to retain control

and prevent scratches, and to avoid injury to the operator and other

7-8

;':~~'r";'';'~-;:~r.~';~:-~'. PROVIDE OF DRILL

FIGURE 16. GRIP OF DRILL MOTOR

----- ............. +

LESS PREFERABLE GRIP OF DRILL MOTOR

APPLICATION OF FORCE IS BELOW THE CENTERliNE OF DRILL AND HENCE, LEVERAGE TILTS THE MOTOR IN AN UPWARD DIRECTION.

CORRECT GRIP OF DRILL MOTOR

APPLICATION OF FORCE IS DIRECTLY BEHIND CENTERLINE OF DRILL.

FIGURE 17. GRIP OF DRILL MOTOR

7-9

workers. Twelve-inch drills tend to whip because of excessive runout

and are a hazard if not controlled. Using a drill guide made from

micarta dowel will control the whipping. Another method is to loosely

grasp the extension drill between the forefinger and thumb (see

Figure 13). Do not grip tightly, since the friction can generate suffi­

cient heat to burn the fingers.

7-7. PERPENDICULAR HOLES

Holes must be drilled "normal" to the surface that the fastener head

will seat against, unless specified otherwise. Normal means at 90 ±

112 degrees to the surface, or perpendicular; for contoured surfaces it

means 90 degrees to the point of tangency. Technically, it is impossi­

ble to drill a concentric (perfectly round) hole at any angle other than

90 degrees to the surface. This is illustrated in Figure 18. The drilling

angle has been exaggerated to clearly illustrate the hole elongation.

The amount of hole elongation, of course, will vary with malangu­

larity.

The smaller the hole tolerance, the more likely that malangularity will

elongate the hole beyond the maximum hole size. The use of drill

bushings in tooling fixtures, such as drill plates, drill blocks, drill jigs,

and drill tables, not only provides more assurance of perpendicular

holes, but also reduces chatter and the tendency of the drill to wander.

(See Figure 19).

7-10

NOTE: THE HOLE DIAMETER AT THE PENETRATION AND EXIT SURFACES (A AND B) IS LARGER THAN THE DRILL DIAMETER (C).

!

'--+If---A

FIGURE 18. DRILLING NON PERPENDICULAR HOLES

CHECK PAD FOR WEAR AND IMBEDDED CHIPS

FIGURE 19. DRILL TABLE AND BUSHING

c

Drill bushings also serve as stabilizers by minimizing the inherent

runout of hole-cutting tools. This dampening effect on tool runout is

an added benefit since it reduces the number of belled and oversized

holes, especially for close-tolerance holes.

7·11

Always use drill bushings for:

a. Drilling pilot holes and all subsequent steps if the holes are

through thick material.

b. Core-drill step before using a piloted reamer.

c. All final hole sizes, except for rivet holes through thin structure.

Freehand drilling (without the aid of drill bushings) of perpendicular

holes is improved by the proper grip of the right hand on the drill

motor (see Figure 17). Also use the unpainted skin as a mirror to help

align the motor properly; the drill should be in an exact straight line

with the reflected image (see Figure 16).

7-8. DRILL LUBRICANT (Reference DPS 3.67-22)

One drill lubricant authorized for assembly shop use is Mirror Base

Lube, DPM 342. This lube should only be used in cases where parts

can be disassembled and individually cleaned and dried after drilling

operations.

Mirror Base Lube that is available in assembly areas has been diluted

with 10 parts of water to 1 part of lubricant. The primary function of

the diluted solution is as a coolant; undiluted Mirror Base Lube may

be used if better lubrication is needed.

The diluted Mirror Base Lube has a maximum storage life of 3 months

and must not be stored in open or galvanized containers. The lubri-

7-12

cant drawn from steel drums must be used from standard pressure

pot or plastic containers only. The container must be labeled and the

expiration date noted.

Mirror Base Lube may be used on partially completed and sealed

assemblies provided it is applied very lightly to contain the lubricant

within the hole. Use of lubricant in a sealed area must be as follows:

a. Dip the cutting tool into the lubricant and allow the excess to run

or drip off the end.

b. Remove all residue with a clean water-dampened (not sopping)

cloth and then wipe dry. Since the lubricant is water soluble, use

water for cleanup purposes, not solvent.

To obtain proper sealant adhesive, the surface must be chemically

clean. The use of petroleum-base lubricants or beeswax is prohibited.

Products of this type have a tendency to bleed into the pores of the

metal and cannot be completely removed by the solvent washing

methods used in assembly departments.

Use Metal Working Fluid, DPM 5389 or 6005, for drilling steels,

titanium, Inconel, and aluminum. For aluminum alloys and graphite­

epoxy composites, use High-Speed Drilling Fluid, DPM 5172. The

primary functions of a drill lubricant are to cool and to reduce friction.

The advantages of using a lubricant are:

a. Increases tool life.

7-13

b. Improves chip removal.

c. Smoother hole wall finish that enhances fatigue life.

d. Reduces heat expansion of cutting tool, thereby rninirrrizing the

chance of exceeding the hole size limitations.

e. Retards the tendency of clad material (nearly pure aluminum) to

build up on reamer lands.

f. Reduces heat transfer from the cutting tool to the metal.

7-9. PILOT HOLE SIZES

Pilot holes are normally required prior to using the final drill. The

achievement of quality holes should always be the criterion for selec­

ting the step drill procedure. Therefore, the following information

should not be regarded as mandatory:

a. A No. 40 (0.098-inch) pilot hole is optional for No. 30 (0.1285-inch)

drills, depending onthe thickness and hardness of the material to

be drilled.

b. A general rule is that the pilot hole should be about one-half the

next hole size.

c. A No. 30 (0.1285-inch) drill is recommended for drilling pilot holes

for 5/32-,3/16-, and 1I4-inch holes.

d. For thick material and hard alloys, a No. 40 (0.098-inch) drill may

be practical to use as a pilot drill. However, it should be noted that

the drill bends very easily and may result in additional runout.

7-14

This poor torsional rigidity is typical of all small-diameter hole­

cutting tools and can be minimized by the use of:

1. Drill bushings to make the drill more rigid.

2. Short-length drills, core drills, and reamers.

3. Correct feed rate.

Predrill steps, before the final hole sizing, may vary in size because of

interim assembly processes, such as countersinking, dimpling, and

coining.

7·10. DISCREPANT HOLES CREATED BY GAPS

Drilling through multiple parts requires correct positioning and use

of clamping devices to eliminate all gaps prior to and during the drill­

ing operation.

Figure 20 shows that a bolt installation would require rereaming and

subsequent oversizing of the hole. A lockbolt pulled into the hole by an

installation gun (3,000 to 5,000 PSn will broach the dotted portion of

the hole.

Figure 21 shows that thin-gauge materials must always be backed up

to prevent sheet separation or distortion during the drilling opera­

tion.

7·15

EXCESS~ no BURRS ~

- DRILL DIRECTION

ill DRILLED WITH GAP

o

NOTE: MALANGULARITY OF HOLE

NECESSARY TO FORCE FASTENER INTO HOLE

HOLE ALIGNMENT AFTER RE-ASSEMBL Y

® FIGURE 20. DRILLING OF STRUCTURE WITH GAP

GAP CREATED BY DRILLING PRESSURE

® ® FIGURE 21. DRILLING FLEXIBLE OR THIN MATERIAL WITHOUT BACKUP SUPPORT

7·16

7-11. DRILLING TECHNIQUES

"Woodpeckering" (removal of drill from hole to facilitate chip

removal) may be required for deep drilling of pilot holes, but should be

avoided during the final sizing step.

"Sawing" (alternate pushing and pulling motion) of the drill after a

breakthrough of the material is usually due to habit and not because it

is necessary. This practice enlarges the hole and is wasted effort and

time. If a fastener fits too tightly, check:

a. The hole-cutting tool for proper size and excessive wear.

b. The fastener diameter to make sure it agrees with the tolerances.

c. Mating parts for accurate hole alignment.

7-12. REAMING TECHNIQUES

Techniques for reaming close tolerance holes are listed in Table 3. The

DON'T column lists common errors that cause oversize holes.

Note that the direction of reamer spirals, relative to the motor chuck

rotation, is such that the reamer will not pull itself into the hole.

Therefore, more force or feed is required than for drilling. Failure to

apply sufficient feed to a reamer will result in belled holes.

A flex drive unit is recommended when hand-reaming close-tolerance

holes. It is an aid in maintaining concentricity and reducing elon-

7·17

TABLE 3 REAMING TECHNIQUES FOR CLOSE·TOLERANCE HOLES

STEPS

1. INSERT PILOT OF REAMER INTO CORE-DRILLED HOLE.

DO

IF DRILL BUSHING IS NOT USED, ALIGN CORRECTLY WITH CORE­DRILLED HOLE BY FEELING AND OBSERVING MOTOR ANGULARITY_

ALLOW CLEARANCE BETWEEN CUTTING LIPS OF REAMER AND SURFACE OF MATERIAL; THEN START MOTOR.

1=T r- LIP CLEARANCE­'I I APPROX 1/2 INCH

~REAMER

JJ z:::.;OF ROTATION

CORRECT METHOD

DON'T

FORCE PILOT INTO HOLE; SHOULD FIT FREELY (ABOUT 0.002 CLEARANCE)_

BIND PILOT OF REAMER; INDICATES MALANGULARITY WITH CORE-DRILLED HOLE.

CONTACT SURFACE OF MATERIAL WITH CUTTING LIPS; THEN START MOTOR ROTATION. THIS CAUSES MOTOR TO LURCH.

PILOT~

~~ INCORRECT METHOD

2. START MOTOR BEFORE APPLYING FEED.

APPLY ENOUGH FEED TO QUICKLY FINGER-CONTROL SPEED OF MOTOR. PENETRATE MATERIAL.

APPLY CONTINUOUS FEED UNTIL REAMER BREAKS THROUGH OPPOSiTE SIDE OF MATERIAL.

3. STOP MOTOR AND STOP ROTATION AND FEED. PENETRATION IMMEDIATELY

UPON BREAKTHROUGH.

4. REMOVE REAMER FROM HOLE

HOLD MOTOR FIRMLY TO PREVENT TILTING.

AS REAMER IS PULLED FROM HOLE, ROTATE MOTOR CHUCK BY HAND IN A CLOCKWISE DIRECTION (SAME DIRECTION AS MOTOR ROTATES).

7-18

ALLOW MOTOR TO STALL.

APPLY FEED LIGHTLY. THERE IS A TENDENCY TO UNDERFEED FOR ALUMINUM ALLOYS.

ALLOW REAMER TO PENETRATE THROUGH HOLE OVER 1 INCH.

PERMIT MOTOR TO TILT AT MOMENT OF BREAKTHROUGH. FAILURE TO CONTROL RESULTS IN ELONGATED HOLES.

USE AIR POWER OF MOTOR TO REMOVE REAMER. THE FEWER THE MOTOR REVOLUTIONS, THE BETTER.

RELAX AND ALLOW MOTOR TO SAG.

ROTATE REAMER COUNTERCLOCKWISE. CHIPS ARE TRAPPED BETWEEN REAMER LANDS AND HOLE WALL, RESULTING IN NICKED HOLE WALL SURFACE.

gated, oversize holes. Torsional rigidity (stiffness) is improved and

shorter reamers may be used, reducing runout (see Figure 22).

C-652-( )-(GT)

C-652-74910-(GT) REAMER WITH A FLAT GROUND

~~FLRDR_IV~E U_N ..... IT'--__ ON=S_HANK. ALIGN WITH

O -- SETSCREW.

'"-------i ~""-------7~ ~PILOT I-LENGTHi

SOCKET SET SCREW TO RETAIN REAMER SHANK

FIGURE 22. FLEX DRIVE UNIT

(MINIMUM 2 x DIAMETER OF REAMER BODY)

The tool is capable of providing a slight flex and thereby creates a

tendency for the reamer pilot to follow the pilot hole. This overcomes

slight movements of the hand while reaming. The key to obtaining a

close-tolerance hole with this tool is a 90-degree pilot hole.

Select the flex drive unit from the data shown below (Reference DPS

3.67-22):

C-652-74910

[BasiC Tool No.

21 GT 1 L General Tool I For reamers with O.188-inch shank

23 1-For reamers with O.311-inch shank

3 L For reamers with 0.435-inch shank

7-19

7-13. DRILLING OF STEEL, INCONEL, AND TITANIUM METALS (Reference DPS 3-67-22)

The induction of high heat into metals during the drilling process is

serious, since it causes a loss in mechanical properties and lessens

resistance to corrosion. Stainless steel, Inconel, and titanium alloys

are very hard metals and high temperatures are generated by using

incorrect hole-cutting tools, feeds, and speeds. These materials dis­

sipate heat very slowly, and heat from the drilling operation is

therefore concentrated at the hole wall surface. High temperatures

alter the grain structure and induce residual stresses that cause inter­

granular cracks.

At the time of drilling, the material (including aluminum) should

never be above touch temperature (approximately 130°F). If there is

any indication that the quality of the material has been adversely

affected by drilling, make a hardness test.

Do not depend on discoloration of the metal or primer as evidence of

overheating. It should always be remembered that many discrepan­

cies are not visible to either the mechanic or the inspector. Therefore,

ensuring structural integrity is directly dependent upon the will­

ingness of the assembler to follow the procedures conscientiously.

These procedures are based on laboratory tests that induced the least

amount of heat in the materials and provided the longest fatigue life.

Table 4 is a page excerpted from the noted manual. It is shown here as

an example of hole-cutting tools for O.OOl-inch-tolerance holes for 7-20

" '"

TABLE 4 EXCERPT FROM TOOL DESIGN "HOLE PREPARATION MANUAL C652·5076260·PDSI"

fAITENfI DATA CUlTlN T CA CO NT IN IN .. E

NOMINAL HOLE DOUBlE MARGIN CYliNDRICAl METHODi$', OR CPS

SIZE TOLERANCE DRillS (i) DRILLS CORE DRillS REAMERS PlUC TABLE NUMBER.

H 06 .1~909?5 72157·128 .001 ·1 -070 55076260 ·5 •. 7.

A =30 (.12851 .1710 x .1270 .1895/.1700 .189S/.190S ·8. ·20. ·21. ·22

N tj4 .2495fS05 72157·191 .002 ·2 ··071 S·5076260 ·5.·7

D =11(.19101 .2344 x .1900 .2495 x .2330 .2495/.2505 ·8. ·20. ·21. ·22

F 5/16 .31~i'313O 72157·250 .003 ·3 -072 S·5076260 ·5.·7

E 1/4 (,25001 .2969 x .2485 .3120 x .2950 .3120/.3130 .s. ·20. ·21, ·22

E y8 .3745/3755

72157·312 .004 -4 -073 5·5076260 ·5,·7

D 5116 (.3125) .3594 x .3110 .3745 x .3580 .3745/.3755 .s, ·20, ·21, ·22

7f6 ,437of380 72157·375 .005 ·5 -074 S·5076260 ·5, .7,

3/8 (.3750) .4219 x .3740 .4370 x .4205 .4370/ .4380 .s, ·20, ·21, ·22

/ / ._.

/ / / / / /

STAN AND EfERENCE UMENTS ~I 1 DOUBlE MARGIN DRilLS MAY BE USED IN liEU Of DRill AND CORE DRilL

NAS BIB, DAC 3395B, ENGIN.EERING DRAFTING MANUAL SEOUENCEJREFER TO OPS 3.67-22 fOR lIMITATIONS.1

0SEE SHEETS es·;v, 8S·v fOR CUTTINC TOOL REfERENCE SKETCHES,CENERAl TOOL NUMBERS,ANO TOOLING SEQUENCE DATA.

~ FAillNER DESCRIPTION BOLT AND SCREW HOLE CUTTING TOOL SELECTION

3116 TO 7116 EXTRA CLOSE FIT CLASS A & VI

fOR NOMINA.L SIZE FASTENERS IN ALUMINUM, STEEL OR ALUMINUM/STEEL COMBINATION

------ ---~-~ - ~--~~--

FIRST ISSUE 1976 REVISED DATE 1·2·78

PAGE NO. BOLT AND SCA

bolts and screws. It lists the drill, core drill, and reamer to be used for

various diameters. This is typical for other fasteners. Cutting tools

are also given for drilling and/or reaming for oversize fasteners.

The manual also specifies that rivet holes require core drill usage for

drilling steel and titanium parts or in any combination with aluminum

alloys.

The core drill induces less heat into the materials and will cut away

the austenitic material (carbon, etc.) that may be created by the

predrill step (see Figure 23). Coordinate these requirements with the

motor speeds recommended in Table 3, and with the usage of lubri­

cants outlined in Paragraph 7-8, "Drill Lubricants."

When drilling holes through a combination of dissimilar alloys (such

as aluminum and steel), always use the feed and speed for the harder

alloy. Where possible, always drill from the harder alloy into the

softer one.

Upon contact with the material, immediately apply cutting feed to the

drill. Do not permit the drill to dwell on the metal without cutting.

Use enough force to keep the drill cutting continuously.

Cobalt drills are preferred for predrilling and are mandatory if the

material thickness is greater than the fastener diameter.

7-22

PHOTOMICROGRAPH OF VICINITY AROUND DRILLED HOLE (MAG 350X). THE AUSTENITIC LAYER AT THE HOLE WALL SURFACE WAS FORMED DURING THE DRILLING OPERATION AS A RESULT OF OVERHEATING. SINCE THIS LAYER IS MORE DENSE THAN PARENT MATERIAL, IT IS PUT IN TENSION; THUS RESIDUAL STRESSES ARE PRODUCED THAT ARE IN EXCESS OF THE YIELD POINT. RESULTS ARE SHOWN IN THE LOWER PHOTO.

PHOTOMICROGRAPH (MAG 300X) OF INTERGRANULAR FAILURE IN PARENT MATERIAl.

17,7 PH STAINLESS STEEL

HOLE WALL

LAYER OF AUSTENITE, A CONSTITUENT OF STEEL UNDER CERTAIN CONDITIONS

INTERGRANULAR CRACK (GRAIN SEPARATION)

FIGURE 23. EFFECTS OF OVERHEATING METALS 7·23

7-14. DRILLING OF GRAPIDTE EPOXY-COMPOSITES (Reference DPS 3.67-22 and -22.1)

Machined and drilled surfaces should show no indications of overheat­

ing. Overheating has occurred when the graphite-epoxy surface has

turned a brownish-black.

Drilled or reamed holes should have a maximum surface roughness

ofl~.

Tool life is limited when composites are being drilled. Cutters should

be replaced when there is tool chatter, chipped cutting edges, over­

heated materials, excessive wear of cutting edges, delamination, or

splintering.

- NOT ACCEPTABLE ACCEPTABLE

FIGURE 24. HOLE SPLINTER CONDITION

When drilling holes where the drill exit surface is a graphite-epoxy

composite, cover the drill exit surface with a masonite or fiberglass

backup to prevent splintering (see Figure 24). The backup must be

held in close contact with the workpiece by clamping.

7-24

Whenadrilllubricantisrequired(ReferenceDPS3.67-22.1)useDPM

5172. High-speed drilling (20,000 rpm) without lubricant is pro­

hibited.

Graphite dust and drill lube residue should be removed from holes

prior to fastener installation. Use 1, 1, 1 trichloroethane (DPM 5792)

as the cleaning agent. A dampened clean cloth, using the above sol­

vent, may be used.

Graphite-epoxy should be countersunk with a radiused, piloted, car­

bide cutter rotated at 2,000 rpm maximum speed (Figure 25). The cut­

ter must be rotating before it contacts the graphite to prevent

splintering. Slight splintering around holes to be countersunk is

acceptable if there is no splintering after countersinking.

When required, the edges of holes for protruding head fasteners

should be broken with a diamond-plated countersink cutter (TD

562R2.2).

GRAPHITE-EPOXY COMPOSITE

FIGURE 25. EDGE BREAK

7-25

Graphite-Epoxy Composite Structure Only

When holes are prepared in graphite-epoxy structure only, use the

following procedure:

Step 1: Drill with a carbide-type twist drill or a carbide flat flute

drill (TFIM 25.0253). For 1/8- through 3/8-inch diame­

ter, use 900 to 2,700 rpm drill motors with feed rates of

30 to 45 seconds per inch.

Step 2: If necessary to meet specified hole tolerances, use a car­

bide reamer.

Back up the drill exit side to prevent splintering and delamina­

tion.

Graphite-Epoxy Composite with Aluminum and/or Titanium Substructure

When drilling holes in a combination of materials, as noted above, use

the following procedure:

Step 1: Drill through the structure with carbide twist drills

using feed and speeds for aluminum or titanium per DPS

3.67-22.

Step 2: If necessary to meet specified hole tolerances, ream

holes to final size using carbide reamers. Use lI64-inch

undersize drill in Step 1 and ream to final size.

Use DPM 5172 dri11lubricant for drilling and/or reaming.

7·26

Aluminum or Titanium with Graphite-Epoxy Composite Substructure

When drilling holes in a combination of materials, as noted above, use

the same procedure specified in the previous paragraph.

NOTE: This type of joint requires that the drill exit side of the

graphite be backed up with aluminum or plastic material.

Graphite-Epoxy Composite Joined with Titanium and Aluminum

When drilling holes in a combination of materials, as noted above, use

the following procedure (see Figure 26):

STEP 1 STEP 2 STEP 3 STEP 4

ji:':=~=in1::::~~~~_-GRAPHITE .---....--TITANIUM 1\~~;4-- GRAPHITE ALUMINUM

FIGURE 26. COMBINATION GRAPHITE, TITANIUM, GRAPHITE, AND ALUMINUM SUBSTRUCTURE

Step 1: .Drill graphite-epoxy up to the titanium with carbide

twist drills using feeds and speeds for aluminum drilling

per DPS 3.67-22.

Step 2: Drill titanium up to the graphite-epoxy with twist drills

using feeds and speeds for titanium drilling per DPS

3.67-22. 7-27

Step 3: Drill through the graphite-epoxy with carbide twist

drills using feeds and speeds for aluminum drilling per

DPS 3.67-22.

Step 4: If necessary to meet specified hole tolerances, ream

holes to final size with a carbide reamer using feeds and

speeds for titanium drilling per DPS 3.67-22.

Use drill lubricant (DPM 5172) for drilling and reaming.

Safety

Where no drill lubricant is used, the dust from machining and drilling

graphite-epoxy composites must be collected in a vacuum system and

the operator must wear a respirator.

Comply with Occupational Safety requirements for hole drilling and

trimming of graphite-epoxy composite materials (Reference: DAC

Safety Manual).

7-28

7-15. SUMMARY OF STEPS PRIOR TO DRILLING

Determine the final hole size and limits of tolerance from the

blueprint, method drawing, or fastener DPS. It is also important to

know the approximate thickness of the joint and the types of metal

alloys.

This information is necessary for the proper selection of drill motor

RPM. The speed used may be slower than the recommended RPM,

but not faster.

When selecting cutting tools and drilling steps, check accessibility,

tolerances, hardness, and thickness of materials.

Use a drill lubricant for drilling steel, Inconel, and titanium, and also

for reaming close-tolerance (O.OOl-inch) holes. Use drill bushings to

ensure proper hole angularity, concentricity, and tolerance.

Prior to drilling, check parts for proper clearance, edge distance, and

location against jig stops and pads. Mating parts must fit snugly, free

of distortion, preload, and gaps.

Visually inspect the cutting tool for size, condition, and runout. The

smaller the hole tolerance, the more important it is to use drilling aids

to reduce runout.

The first time a tool is used, check it on a piece of scrap material to

make sure it is accurate. This is not necessary for holes having a

tolerance of 0.006 inch or greater.

7-29

8·1. GENERAL

SECTION 8

CHECKING OF HOLE SIZES

Attachment holes drilled with conventional air motors have a tend­

ency to be belled or enlarged on the drill entrance side of the material.

The size of the hole gets progressively smaller toward the drill exit

side of the material (see Figure 27).

Belled holes are usually caused by:

a. Vibration and wobble of the cutting tool. This condition lessens

slightly as the drill or reamer cuts deeper into the material.

b. Excessive pressure applied at the time the motor is started. The

outer portion of the drill lips have a small bearing area because of

the pilot hole, and the drill has a tendency to grab.

Lack of motor rigidity and the timing of any hand movement pro­

duces holes of many configurations. The cone-shaped hole, shown in C

of Figure 28, is typical of most assembly-drilled holes. The hole

tolerance is the determining factor as to its acceptability.

Lack of motor rigidity may cause tapered holes (see Figure 28).

Detection of discrepant holes is more accurate if checked from the

entrance side. Holes within tolerance near this surface are unlikely to

be oversize in the middle or drill exit side. 8-1

\L----...J1 r DRILL ENTRANCE SIDE

( rBEL~EO PORTIO. OF HOLE

LHolE IS TIGHTER ON THIS SlOE

FIGURE 27. BELLED HOLE

DO DO o o A B c

FIGURE 28. TAPERED HOLES

Belled and tapered holes reduce the material bearing area for

fasteners loaded in shear. Therefore, they are undesirable and unac­

ceptable if the discrepancy is more than the maximum tolerance of the

hole.

8-2. GO AND NO-GO PLUG GAGES

These gages (Figure 29) are available in many sizes for different

types offasteners. If used properly, this type of hole gage can quickly

and efficiently detect discrepant holes. The disadvantage of the gage

is the need to use other measuring devices to find the actual dimen­

sion of oversize holes for engineering salvage information.

8·2

REMOVABLE CYLINDRICAL PLUGS

FIGURE 29. GO AND NO·GO PLUG GAGE

Before using a plug gage the first time, use a micrometer (Figure 30)

to verify the two sizes stamped on the holder. The "Go" end has a

tolerance of +0.0000, -0.0002-inch. The tolerance of the "No-Go"

end is + 0.0001, - 0.0001-inch.

The "Go" end (colored green) provides assurance that the hole is not

undersize if the gage passes through the hole. The "No-Go" end (col­

ored red) provides assurance that the hole is not over the maximum

size if the red end cannot enter the hole, either totally or partially.

~-~---RATCHET STOP

FIGURE 30. MICROMETER CALIPER

8·3

Figure 31 shows a modified type of "No-Go" gage. Rotation of the

gage will allow for a more positive identification of elongated holes.

FIGURE 31. MODIFIED NO·GO PLUG GAGE

Personnel can quickly become skilled in using the gages by using sight

and feel. Gages should be used from the final drill or reamer entrance

side. The following sequence is suggested:

a. "Go" end of gage.

1. Gage does not enter the hole; hole is therefore undersize and

not acceptable.

2. Gage passes through the hole and provides assurance that

hole is not undersize.

(a) A tight fit through the entire hole is a good indication that

the hole is within the maximum tolerance.

(b) A loose fit is a caution that the hole may be oversize. The

gage is most likely to be loose at the drill entrance side

and tight near the drill exit side.

3. Observe the gage fit around the edge.

(a) A snug, no-gap fit at the hole edge indicates that the hole

is within tolerance.

(b) Ifthere is a gap, proceed to step b.

8-4

b. "No-Go" end of gage.

1. Gage enters the hole; hole is oversize and not acceptable.

2. Gage does not enter the hole; hole may be acceptable. Proceed

to next step.

3. ~lace gage over the hole and observe around the gage end for

the hole edge.

(a) If no portion of the hole edge is visible, hole is acceptable.

(b) If any part of the hole edge can be seen, hole is rejectable.

8-3. BALL GAGE AND MICROMETER

Ball gages come in various sizes and are used to accurately measure

the diameters of holes. Like most other tools, a ball gage is not infalli­

ble; its accuracy depends on the skill, knowledge, and experience of

the user. To properly locate the gage in the hole, perform the follow­

ingsteps:

a. Rotate the ball gage inside of the hole and adjust until it touches

the hole wall; drag should be very light.

b. Rotate the gage again; if the drag is not continuous, the hole is

elongated. Readjust the gage to include elongation.

c. Move gage to and fro in a longitudinal direction to detect belled or

tapered holes.

8-5

After the final adjustment has been made on the ball gage, measure it

with a certified micrometer. This is the second time an accurate

measurement depends on a delicate sense of feel, and requires

extreme care.

8-4. INTRIMIKS

To ensure quality holes within engineering tolerances, it is recom­

mended that Intrimiks be used wherever possible (see Figure 32).

FIGURE 32. INTRIMIKS

Selection of gage size is by range. For example, one size gage

(smallest available) is used for measuring any hole size between 0.275

and 0.350 inch (minimum-maximum limitation). This gage can be used

for verifying the size of a hole specified to be 0.312 to 0.313 inch. This

8-6

particular gage, however, cannot be used for a 0.2495- to 0.2505-inch

hole (hole is too small), nor can it be used for a 0.375- to 0.376-inchhole

(gage is too small). Use the next larger size gage. (Micrometers

graduated in metric millimeter increments are also available.)

Prior to using gages, verify the accuracy by using provided check

blocks.

Use the ratchet on the mike for final adjustment to provide consistent

repeat accuracy.

Three contact points, spaced 120 degrees apart, touch the hole wall

surface. Readout is obtained with the attached micrometer.

8-7

BURRS ARE MINIMAL AND EASILY REMOVED IF SHEETS ARE TIGHT AND SHARP HOLE DRILLING

TOOLS ARE USED ~ BURR ON DRILL EXIT SIDE

~ EXCESSIVE BURR DUE TO GAP

DRILL DIRECTION-- ,/

[]] ~LGAP

FIGURE 33. EXCESSIVE BURRS DUE TO GAP

8-8

SECTION 9

DE BURRING OF HOLES

9-1. GENERAL

Hole burrs, located on the drill exit side, consist of small portions of material that were pushed out (not cut) because of the force applied to

the drill. The use of dull hole-cutting tools and excessive feed creates large burrs. Excessive motor speed for drilling and reaming steel, Inconel, and titanium, or in combination with aluminum, produces burrs that are larger than normal.

Since the clad on the surface of aluminum alloys is soft, it tends to pro­

duce heavier hole burrs than nonclad aluminum alloys. Thick alumi­num alloy has thick clad coating; therefore, larger burrs are produced.

Clamp materials together tightly before drilling to minimize burrs

between faying surfaces (see Figure 33).

Hole burrs prevent metal-to-metal contact of the mating surfaces and

can cause fasteners to loosen under repeated surface loads and vibra­tion. '1\1so, fretting corrosion is induced by the wearing action of the burrs on the mating surfaces. Proper burr removal is essential and

mandatory to ensure structural integrity.

9·1

CAUTION

In assembly areas, never grind or sand to remove burrs, since

this will adversely affect the material finish and hardness.

Burr removal for fasteners in high-stressed critical fatigue joints shall

be accomplished as specified on the engineering drawing. Check prior

to deburring holes other than for aluminum alloy rivets.

9-2. RIVET HOLES (Reference DPS 3.67-22)

Use a vixen block or channel deburringtool (see Figure 34) to remove

rivet hole burrs on bare, nonclad, aluminum alloy surfaces except on

exterior skin surfaces. Burrs in excess of 0.002 inch high (approx­

imately one-half the thickness of this page) are not acceptable. Use

the following techniques and precautions:

a. The tool should cut clean with one or two strokes. Clean the chips

from the tool after each stroke. If these chips are not cleared

away, they become wedged in the cutting teeth of the tool and will

scratch the surface of the material.

b. If burrs stick to the cutting edges, or if the edges are dull or

chipped, replace the tool.

c. Do not use on exterior skin surfaces.

d. Use only a forward-cutting stroke. Do not scrub.

e. Apply light pressure; too much pressure will cause the tool to dig

and grab.

9-2

SET SCREWS

ASSURE THAT EDGE RADII PREVENT CONTACT WITH SKIN SURFACES

VIXEN BLOCK CUTIING TEETH MUST BE SURFACE-GROUND, LEAVING 0.005 FLATS

11f2-INCH VIXEN FILE

VIXEN CHANNEL DEBURRING TOOL

FIGURE 34. VIXEN FILE DEBURRING TOOLS

9·3

On appearance areas, holes may be individually deburred with a

100-to 120-degree countersink cutter in a low~RPM motor. This type

of hole deburring requires caution; remove only the sharp edge.

Removing too much material reduces the bearing area for the

fastener. See Figure 35 for dimensional limitations.

Never use 82-degree countersink cutters for burr removal. A cut

made with this tool, of sufficient width to remove the burr, will result

in a chamfer depth greater than that obtained with a 100-degree

countersink cutter. Figure 36 illustrates the result from using two

different degree cutters.

9-3. DIMPLED HOLES (Reference DPS 3.67-2)

Removal of burrs from holes to be dimpled must be performed per the

applicable DPS by a qualified dimple operator. Before dimpling, use

one of the following methods to remove all sharp and protruding

edges caused by drilling:

a. Vixen deburring block, subject to limitations of the DPS.

b. A 100- to nO-degree countersink cutter driven at low RPM is

mandatory for all screw dimples (see Figure 37). The material

removed by this operation must not exceed 25 percent of the total

sheet thickness.

9-4

n /.005 MAXIMUM WIDTH OF CUT ~ FOR BURR REMOVAL D~·olO MAXIMUM WIDTH OF CUT

FOR BURR REMOVAL

~

-D- IF MATERIAL IS MINIMUM MATERIAL THICKNESS FOR COUNTERSINKING PER S5076260 ¥ IF MATERIAL IS OVER THE

MINIMUM MATERIAL TlHCKNESS FOR COUNTERSINKING PER S5076260

FIGURE 35. DEBURRING FOR RIVET HOLES IN APPEARANCE AREAS ONLY

DEPTH IS LESS THAN 100° 820 ~EPTH IS GREATER THAN

"" eHAjFER 1 ') Y . '\ / 100" CHAMFER

f I DO If -1 ~ ~ ~

CORRECT NOT ACCEPTABLE

NOTE: CHAMFERS ARE ENLARGED FOR CLARITY

THE OVERALL WIDTHS OF THE TWO CHAMFERS ARE EQUAL; WIDTH IS THE MINIMAL MATERIAL REQUIRED TO REMOVE BURR.

THE WIDTH OF CHAMFER IS 0.005INCH~MAXIMUM FOR COUNTERSUNK MINIMUM MATERIAL THICKNESS; OTHERWISE, 0.010 INCH MAXIMUM.

FIGURE 36. BURR REMOVAL

100° TO 110°

~--~,~,>~----~ ) " '" >~25% OR LESS

DIMPLE DOWN SIDEJ "-"

FIGURE 37. HOLE DEBURRING FOR SCREW DIMPLING

9·5

NOTE

Deburring both sides of the sheet is permissible, pro­

viding total material removed is not more than 25 percent

of the sheet thickness.

When ordinary deburring methods fail to prevent radial cracks,

polish the hole before dimpling.

9-4. STEEL AND TITANIUM MATERIALS (Reference DPS

3.67-22)

To deburr holes on steel and titanium metals, use a fine-tooth, cone­

type, rotary file, 04522-8Dl-161 (GD-60 degrees), or a 100- to

120-degree countersink cutter in a low-RPM motor. Motor speed for

deburring of holes should be one-third to one-half of the RPM recom­

mended for drilling. Balance the feed and speed to prevent chatter

marks and heat induction.

9-5. RING-COINED HOLES (Reference DPS 3.67-23)

Before ring-coining, deburr holes by using a flat deburring tool, such

as a vixen block. Do not use a countersink cutter.

The engineering drawing may specify the method to use, especially

for high-stressed parts.

9·6

NOTE

Countersinking and breaking hole edges, if required, shall be

accomplished after the coining operation is complete.

9-6. HOLE EXPANSION (Reference DPS 3.67-25)

Deburr only the ridges protruding above the surface, using No. 240

or finer abrasive paper. Be careful notto chamfer the hole edge.

9-7. PIN STRESS COINING - HOLES AND COUNTERSINKS (Reference DPS 3.67-56)

The above coining methods require hole edges to be chamfered prior

to coining. These methods eliminate the need for deburring. Refer to

the above DPSs for chamfer dimensions and tolerances.

9-7

c. Distort thin materials.

d. Tear the hole in thin materials.

e. Create gaps and built-in stresses.

f. Peel the anticorrosion coating from the fastener.

Clearance fit installations may require a slight force to overcome fric­

tion between the hole wall and the fastener. Minimum hole sizes and

maximum fastener diameters produce this type of fit. If thumb

pressure is not enough to insert fasteners into clearance fit holes, the

problem is usually hole misalignment, but it may also be:

a. Burrs were not removed, or a chip is trapped between mating sur­

faces at the hole edge. The hole can be cleared by using an align­

ment pin or ice pick; use carefully to avoid distortion of the hole.

b. The wrong size cutting tool was used; there is seldom an optional

size that will provide the minimum and maximum hole tolerance.

c. The margins on the cutting tool may be badly worn. An undersize

tool is likely if it has been used to drill hard alloys, such as stainless

steel or titanium.

d. Size of the fastener may be greater than the maximum specifica­

tion. This seldom happens, but if everything else is satisfactory,

ch~ck the actual size of the fastener with its specification.

10-2

Some causes of misalignment are:

a. The use of clecos to obtain hole alignment is a common practice.

However, a cleco is not a precision tool and is not satisfactory for

accurate alignment of holes. Its one and only function is to hold

parts together temporarily.

NOTE

Clecos will not consistently align holes properly, even for

rivet holes having a 0.005-inch tolerance. Aliowingfor the

permissible variation of the fastener and hole diameter, a

5/32-inch rivet may have a clearance fit of 0.001 to 0.011

inch. If the hole is misaligned only 0.002 inch, there is a

possibility the rivet will not enter the hole freely.

b. A sufficient number of temporary fasteners were not used during

the drilling operation.

c. Failure to spot-rivet allows thin materials (doublers, webs, and

skins) to creep out of alignment during the riveting operation.

d. Failure to eliminate gaps prior to drilling causes hole malangular­

ities, as shown in Figure 38.

Failure to use temporary fasteners creates gaps when close-tolerance

attachments are driven into interference fit holes. Note the sequen­

tial steps in Figure 39. Although the parts were drilled correctly, it is

easy to determine that the reassembly step, in this particular case, is

10-3

MARK INDEX HOLES FOR TEMPORARY FASTENER USAGE. RE-INSTALL TEMPORARY FASTENERS IN SAME HOLES UPON RE-ASSEMBL Y.

o o o o o

FIGURE 40. INDEX HOLES

10·6

SECTION 11 DRA~GSYMBOLSFORFASTENERS

11-1. GENERAL

The fastener code system applies to all types of fasteners if the instal­

lation will cause a permanent deformation of the fastener or if it is

necessary to destroy the fastener to remove it.

The symbol system shown below is explained in Method Drawing

S5076260 and is used to simplify fastener callout and hole prepara­

tion. The symbol includes a single cross, with the intersection at the

location of the fastener. Fastener and hole preparation information is

indicated by an alphanumeric code placed within specific quadrants of

the cross. When the symbol is viewed in a position so that the letters

are upright, the upper left-hand quadrant is northwest, etc.

NWINE SW SE

11-2. NORTHWEST QUADRANT

Fastener identity is shown by a two-letter basic code. The code is

made up of two letters and defines all features of the fastener except

diameter and grip. Explanation of the fastener identity code will be

found in the "General Notes" on the engineering drawing. All of the

11·1

two-letter basic codes are identified in NAS 523.

~ 11-3. NORTHEAST QUADRANT

The fastener diameter and location of the manufactured head are

defined by a letter-number code. The fastener diameter is shown by a

number that represents the diameter (dash number) in the full part

number; this is usually in 32nds of an inch.

The location of the manufactured head of the fastener is defined by

the letter "F" for far side and "N" for near side. When the location of

the manufactured head is obvious or insignificant, the code letter is

left out.

11-4. SOUTHEAST QUADRANT

The fastener length is shown by a dash number that represents the

length in the full part number.

NOTE

Rivet lengths are not specified unless the requirement is more

than 1 inch.

"·2

Lockbolts, Hi-Loks, and most screws are coded by grip length, usu­

ally in increments of 1116 inch.

-h-11-5. SOUTHWEST QUADRANT

Dimple and countersink information is indicated by a letter-number

code consisting of one, two, or three lines. The following information

is from the method drawing for rivet and screw hole preparation,

S5076260:

D-Dimple

D2C

DC

82

No. - Number of dimpled sheets

C - Countersunk

Blank - Install per methods drawing

82 - Angle of upset end if upset into a cavity

11-6. SPECIAL CONSIDERATIONS

For a full explanation of coding, see specific dash numbers of the

methods drawing. (Refer to Table 5; excerpted from 85076260.)

11·3

DRAWING NO. :5076260

/ PAGEN~ __ ~I~.I~ __________ __

. CY' _____ ...::C:HA:N::G~E~LE:.T~TE~R=· 6:::Y===== ______________ DOUG~

TABLES DRAWING SYMBOLS FOR HOLE PREPARATION

The symbol system shown below Is based on NAS 523 which servee to simplify fastener callout and hole preparat ion with a code· in the lower left hand quadrant that defines the method of hole preparation, in accordance with the methods drawing, 8-5076260.

~ DASH NO. THAT REPRESENfS THE DIAHETER III THE FULL PART KO.

LETTER 8ASIC COOE~ II "" MFO. HEAD NEAR SIDE

--....-..... 88/ IN''':-''-------- F. HFD. HEAD FAR SIDE

02e 2-1' DC ___________

...., 82 ~~~~T~OiH T~~i ~ijr~E~!~~S H~E COOING WHICH DEFINES A --/" SPECIFIC M(THOO TO BE USED IN PREPARIHG THE HOLE PER METHODS DRAWING.

o ... DIMPLE NO. c: HUMBER OF SHEETS OlMPLED C :: COUNTERSUNK BLANK :c INSTALL PER METHODS DRAWIKG 82 :: ANGLE OF UPSET EttO IF UPSET

INTO A CAVITY

FOR EXPLANATIOH OF COOING SEE SPECIFIC DASH NUMBERS OF THE METHODS DRAWl HG.

EXCEPTIOtt: Itt DOUBLE FLUSH APPLICATIONS WHERE OIHPLE-<;OUIHERSIICK OPERATIOttS ARE OPTIONAL. THE COOING WilL BE THUS:

ANGLE OF NfO HEAD -,aa1-"'NGlE Of UPSET EHO _~I

INDEX OF DIMPLE AND COUNTERSINK CODES

CODE METHODS DRAWl JIG

DASH JllI(l!If.R

RIVETS SCREWS

COlIIDITIOU

... , -a COUHTERSINK TOP SHEET OR SHEHS

0, 02, 0:3. ETC. -2, -5 All SIIEETS 01 HPLEO

DC 02e. D)C. DIlC, ETC

TWO ANGL(S MfO IIEAD UPSET EHO

xo (UPPER LEFT QUAORANT)

-3. -) .... -18 -7. -7A DIMPLE TOP SHEET; COUlHERSINK

-38. -18 -78 DIMPLE HUMBER Of OUTER SHEETS SPECIfiED; COUNTERSINK

- , -<I

10. -19

RIVET IS UPSET nUSH

DOU8LE FLUSH ~IYETS WITH OPTIOHAL OIHPLE COUHTERSIHK OPERATIONS

DEICER DIMPLE

McDonnell Dougfas Corporation Proprietary Information - Use or d!sclosure of this information is subject to the restriction o:ljhe title page or on the first page of thiS document.

114

Exception: In double-flush applications, where dimple-countersink

operations are optional, the coding will be as follows:

Angle for manufactured head (deg)-wo--+­Angle for upset end (deg) .~~~ I

When it is necessary to indicate the exact installation method, use the

following dimple-countersink coding:

For single-flush rivets, the code consists of only one line, and not more

than three digits.

ocst- ct- mt-Top and middle

sheets dimpled;

bottom sheet

countersink.

Machine countersink

regardless of sheet

thickness or number

of sheets affected.

Inner and outer

sheets dimpled.

For protruding head rivets to be upset flush, the code consists of two

lines.

First line: Indicates the dimple or countersink (or both) opera­

tion for the upset end.

11·5

Second line: Indicates the nominal angle of countersink of the

upset end; 82 degrees is mandatory for upsetting

rivet butts into countersink.

nsc+­U;~I

For double-flush rivets, the code consists of three lines:

First line: Indicates the dimple or countersink (or both) opera­

tion for the manufactured head.

Second line: Indicates the dimple or countersink (or both) opera­

tion for the upset end.

Third line: Indicates the normal angle of dimple or countersink

of the upset end when different from the angle of the

manufactured head; 82 degrees is mandatory.

yt-~Jf-8~ I 8~ I ~~ I

Special cases: When a particular method is required, for example

S5076260-14, it will be noted in the drawing symbol thusly:

~ This type of callout is also typical for other methods.

11·6

No code for dimpling and countersinking is necessary when the

method of installation for flush fasteners (Method Drawing

85076260) is optional. The complete dimpling and countersinking

coding shall be used when it is necessary (1) to restrict the operations

permitted by 85076260 or (2) to authorize deviation from 85076260.

When in doubt, always refer to the general notes on the engineering

drawing.

11-7

1--1 .----... l- DIAMETER ±0.005 OF I I NOMINAL DIMENSION

--r MINIMUM MATERIAL THICKNESS PER S5076260

~------I ----.!

KNIFE EDGE - NO RADIUS AT BOTTOM OF COUNTERSINK WELL

FIGURE 41. TYPICAL 100·DEGREE COUNTERSINK FOR MANUFACTURED HEADS OF FLUSH RIVETS

11·8

12·1. GENERAL

SECTION 12 COUNTERSINKING

Countersinking shall conform to DPS 3.67-3, Countersink for Flush

Attachments, and to Method Drawing S5076260, Rivet and Screw

Hole Preparation. For fasteners other than rivets, refer to the

specific fastener DPS or method drawing. Figure 41 illustrates a typ­ical100-degree countersink for manufactured heads of flush rivets.

The following three rules are excerpts from DPS 3.67-3:

a. All holes must be drilled straight and normal to the surface unless

otherwise specified.

b. Select the tools, speed, and feed that will produce countersinks

that are concentric with the holes and are free from chatter, swirl­

ing chip scratches, and other tool marks.

This is especially important on clad exterior skin surfaces. The

clad coating is thin and is almost pure aluminum (soft) and

therefore easily marred by stop countersink holders.

Check these factors on scrap or test material before countersink­

ing production parts.

c. Adjustable stop countersinks are used in portable electric motors,

air-powered motors, or stationary drill presses. The stop counter­

sink must have an accurate and positive locking adjustment for

12·1

maintaining the proper depth and diameter. The cutters must

also be equipped with a pilot of the proper size to maintain concen­

tricity with the hole and to prevent chatter marks.

12-2. MINIMUM SHEET THICKNESS (Reference DPS 3.67-3)

When countersinking in minimum thickness material, proceed as

follows:

a. Where practicable, countersink on stationary equipment.

b. Where portable equipment must be used, back up the far side of

the material to eliminate enlarged, elongated, or torn countersink

holes.

When countersinking in minimum thickness material or when break­

ing the edge of the hole at the juncture of the hole and countersink,

the hole diameter may enlarge beyond the maximum hole tolerance.

This condition is acceptable providing the hole tolerance is not

exceeded by 0.005 inch maximum, countersink angle and diameter

are correct, and the oversize hole will not create a leak path.

12-3. BELOW MINIMUM SHEET THICKNESS

When countersinking below the minimum sheet thickness (see

Figure 42), proceed as follows (Note: Must have engineering authori­

zation):

a. The part must be countersunk together with the substructure and

without any chips, burrs, or gaps between the members to

12-2

MATERIAL THICKNESS IS LESS THE ORIGINAL HOLE IN TOP SHEET 1 t: THAN THAT SPECIFIED BY IS ENLARGED BY COUNTERSINKING S5076260 l KNIFE EDGE - NO

---"""\ SHOULDER. MOST

T STEEL AND TITANIUM FASTENERS REQUIRE THIS EDGE TO BE CHAMFERED OR

SUBSTRUCTURE PROVIDES BEARING AREA FOR PILOT OF COUNTERSINK cunER

RADIUSED

COUNTERSINK EXTENDS INTO SUBSTRUCTURE

FIGURE 42. COUNTERSINKING BELOW MINIMUM SHEET THICKNESS

eliminate a step condition and to prevent torn or folded-over

countersink holes.

b. If the substructure is of light-gauge material, it may be necessary

to back up the far side of the structure to prevent damage to the

countersink or hole.

12-4. MEASURING COUNTERSINK DIAMETERS

Aerodynamics, leak-proof requirements, and flight stresses make it

absolutely necessary that countersinks meet engineering dimensions.

Countersink diameters are specified in thousandths of an inch, usu­

ally with a tolerance of ± 0.005 inch. Exceptions are specific counter­

sink dimensions called out by engineering drawings or by a fastener

DPS. These permissible but small variations make it impractical to

use the head of a fastener as a guide for countersinking.

12-3

On all flat sheets, use a Trulok or Brencor countersink gage to check

countersink diameters. Select the Trulok countersink gage from

Table 6. Refer to Figure 43 for instructions on using the Trulok.

TABLE 6 TRULOK COUNTERSINK GAGES

LIMITS

TRULOK DEGREE OF GAGE ANGLE MINIMUM MAXIMUM

100·1 100 0.160 0.360 100-2 100 0.360 0.560 100·3 100 0.560 0.780 100·4 100 0.780 1.000 100·5 100 1.000 1.335

82·1 82 0.160 0.360 82·2 82 0.360 0.560 82·3 82 0.560 0.780

Calibrate the Brencor dial indicator gage with the test block. Check

for correct size and degree. Should the gage be dropped or bumped,

recheck calibration.

On assemblies having a 20-inch radius or less, the Trulok gage will not

give accurate readings, and the countersink diameter must be

measured with a scale. Countersinks on curved surfaces are elliptical.

Flush screw heads are always seated "flush" to "low"; rivet heads

are "flush" to "high." Therefore, change the direction of measure­

ment for nomimal countersink dimensions as shown in Figure 44. A

general rule is: for rivets, measure the elliptical countersink in the

widest direction; for screws, in the narrowest direction.

124

1. RESET DIAL BY PULLING UPPER KNURLED KNOB STRAIGHT OUT TO ITS LIMIT.

BE SURE GAGE IS THE SAME ANGLE AS COUNTERSINK, AND THAT ITS RANGE INCLUDES DESIRED COUNTERSINK DIAMETER. DIAMETER IS READ IN THOUSANDTHS OF AN INCH OPPOSITE LINE ON THE CENTER SLIDE. EACH SMALL DIVISION REPRESENTS 0.005 INCH.

2. CHECK GAGE ON CHECK BLOCK IN BOX. GAGE READING SHOULD BE THAT ENGRAVED ON

CHECK BLOCK.

4. PRESS CONICAL HEAD FIRMLY COUNTERSINK UNTIL BODY OF GAGE RESTS SOLIDLY ON SURROUNDING SURFACE.

3. CHECK COUNTERSINK ANGLE WITH POINTED BLADE. ANGLE IS STAMPED ON BLADE.

5. REMOVE GAGE. READ COUNTERSINK

FIGURE 43. INSTRUCTIONS FOR USING THE TRULOK COUNTERSINK GAGE

12·5

CROSS SECTION VIEW

TUBULAR ANO CONTOURED CONFIGURATIONS, 20-INCH RADIUS OR LESS INSIDE CONTOUR

STEEL AND TITANIUM FASTENERS - MEASURE CROSSWISE

TUBULAR AND CONTOURED CONFIGURATIONS, 20-INCH RADIUS OR LESS

RIVETS - MEASURE LENGTHWISE

FIGURE 44. MEASURING COUNTERSINK DIAMETERS

(TUBULAR AND CONTOUR SURFACES)

12-6

NOTE

A flexible scale graduated in hundredths of an inch will pro­

vide better accuracy than fractional dimensions.

Figure 44 illustrates the method for measuring countersinks for

rivets and screws for tubular and inside contours of 20-inch radius or

less. Reverse the direction of measurement for outside contours.

12·5. VERIFYING DEGREE OF COUNTERSUNK HOLES

Both the 82-degree and lOO-degree countersink cutters are used in

assembly processes and-it is not uncommon for the wrong degree of

cutter to be used. It is difficult to visually detect this type of

discrepancy without the use of angle blades, shown in Figures 43

and 45.

VERIFICATION OF CORRECT DEGREE OF COUNTERSINK

DETECTING INCORRECT DEGREE OF COUNTERSINK

FIGURE 45. VERIFYING DEGREE OF COUNTERSUNK HOLES

12-7

POINT OF SHEAR - LIMITED BY DIMPLES SUBJECTED SHEAR STRENGTH OF RIVET TO SHEAR STRESSES

IN THIS AREA

NON-DIMPLED JOINT DIMPLED JOINT

FIGURE 46. DIMPLING

FIGURE 47. DIMPLE DIES

12·8

13-1. GENERAL

SECTION 13 DIMPLING

A function of a fastener is to transmit loads from one part to another.

In a nondimpled joint, the shear load is limited to the shear value of

the fastener itself (see Figure 46).

A dimpled joint can increase the ability of a flush fastener to transfer

shear loads. The load can even exceed the shear value of the fastener,

since the dimples are interlocked and prevent the transmittal of the

entire shear load to the fastener. It is never permissible to counter­

sink when Engineering specifies dimpling.

13-2. EQillPMENT

Hot-dimpling equipment must be certified. The certification due date

must be stamped on the certification decal that is attached to sta­

tionary hot-dimple machines, portable squeezer dimpling equipment,

and control panels. (Reference DQS C5.1-1 AD.)

Dimple dies have a high-grade finish to prevent surface irregularities

in the dimpled material. To protect this finish, dies should be stored

individually to prevent scratches and nicks from other tools, and in

such a way as to prevent corrosive pitting (see Figure 47).

13·1

Misalignment of dimple dies is frequently the cause of discrepant

dimples. If any misalignment of dies is evident, stop production until

Maintenance has corrected the realignment and Quality Assurance

Certification has verified it.

13-3. HOT DIMPLING

The dimpling of a particular metal is governed by its ductility (the

quality of a metal that determines the ease of forming, without crack­

ing, into various shapes). A somewhat brittle material may be made

more ductile by heating it, thereby allowing dimpling. Dimples must

be formed at higher temperatures for titanium, magnesium, and most

(but not all) aluminum alloys. To determine minimum and maximum

temperature requirements for specific materials, refer to

DPS 3.67-2.

When overheated dimples are evident, it is important to determine

the degree and extent of damage. A comparison of the material hard­

ness at the dimple with the hardness of the surrounding area is an

indicator. The degree of discoloration of scorched paint is mean­

ingless since damage may be considerable even with little or no

darkening. Visual inspection of the finished dimple will not necessar­

ily reveal overheating. For an example of the effects of heat on

materials, see Figure 23.

13-2

13-4. CRACKS

Radial and circumferential cracks are common in dimpling and may

be either internal or external (see Figure 48). Use of a lower die

temperature than referenced can result in internal or nonvisible

cracks. Use of either a higher die temperature or a longer dwell time

will result in low-strength dimples.

Circumferential cracks are less common than radial cracks. Reverse

forming of a dimple, or flattening, is never acceptable since it always

produces circumferential cracks. Never redimple shallow or other­

wise unacceptable dimples without documented approval from Proc­

ess Engineering.

Radial cracks are the result of poorly drilled holes, improper deburr­

ing, insufficient heat, or incorrect dwell time.

All cracks, regardless of degree, shall be cause for rejection and must be referred to Liaison Engineering for disposition.

CIRCUM"'ENTIAL INT;"AL C~

CIRCUMFERENTIAL CRACK

RADIAL CRACK

FIGURE 48. TYPES OF DIMPLE CRACKS

13·3

13-5. OTHER QUALITY REQUIREMENTS

The protective wash-off coating on exterior skin surfaces must be

removed prior to all hot- and ambient-temperature dimpling.

Hot and cold dimpling is restricted to qualified and certified

operators.

A satisfactory dimple is well defined and the contour is not changed

by the operation. An overformed dimple is caused by excessive

pressure that overstretches the material. An underformed dimple is

due to insufficient pressure. Figure 49 illustrates these variable con­

ditions. Test strips are used for proper adjustment of equipment

pressure. Test specimens shall be of the same material, alloy, temper,

and thickness as the production part.

Analysis of laboratory tests and past experience prove that strict

adherence to Process Engineering procedures produces quality

dimples. This, coupled with the integrity of the dimple operator, is the

best assurance of quality dimples.

PROPERLY FORMED OVER-FORMED UNDER-FORMED

FIGURE 49. DIMPLE FORMING

13-4

For more detailed information on dimpling, refer to the following

documents:

DPS 3.67-2, Hot and Cold Dimpling (Stationary Equipment)

DPS 3.67-7, Portable Squeezer Dimpling (Elevated and

Ambient Temperature)

DPS 3.67-8, Portable Vibrator Dimpling (Elevated and Ambi­

ent Temperature)

DPS 3.67-37, De-leer Dimpling

S5076260, Method Drawing for Rivet and Screw Hole

Preparation

13·5

?£MANUFACTURED RIVET HEAD

{r-----4__ f NO LEAKAGE O~GAS OR lIQUIO AT THE \ UPSET END LMAXIMUM SWELLING AT THE UPSET END

FIGURE 50. LEAKPROOF RIVET HOLES

LEAK STOPPED BY UPSET END

THE MILLED HEIGHT IS DETERMINED BY AERODYNAMIC REQUIREMENTS < .:;VET UPSET INTO CDUNT"SINK 1

~ EXTERIOR SKIN t '"d INNER STRUCTURE , .•.. ~

MANUFACTURED RIVET HEADJ POSSIBLE LEAK PAT~~ FIGURE 51. NACA RIVET METHOD

13-6

For more detailed information on dimpling, refer to the following

documents:

DPS 3.67-2, Hot and Cold Dimpling (Stationary Equipment)

DPS 3.67-7, Portable Squeezer Dimpling (Elevated and

Ambient Temperature)

DPS 3.67-8, Portable Vibrator Dimpling (Elevated and Ambi­

ent Temperature)

DPS 3.67-37, De-leer Dimpling

S5076260, Method Drawing for Rivet and Screw Hole

Preparation

13-5

r£MANUfACTURED RIVET HEAD

{r-----...,____ ( NO LEAKAGE oW GAS OR LIQUID AT THE \ UPSET END '-MAXIMUM SWELLING AT THE UPSET END

FIGURE 50. LEAKPROOF RIVET HOLES

LEAK STOPPED BY UPSET END

THE MILLED HEIGHT IS DETERMINED BY AERODYNAMIC REQUIREMENTS < :;v," UPS," INTO CDUNTER." 1

8 EXTERIOR SKIN t

MANUFACTURED RIVET HEAD ~ FIGURE 51. NACA RIVET METHOD

13-6

SECTION 14

RIVET ORIENTATION

Before proceeding into countersinking requirements, an understand­

ing of rivet orientation will provide a better insight into the require­

ments for using the various methods of rivet installation.

The maximum swelling of the rivet shank is at the upset or butt end of

the rivet (see Figure 50). The grain structure is altered to a great

extent in this area. It is of fine texture and closely packed, because of

the cold working of the rivet during the process of forming the upset

head.

If the hole is of the proper size and the rivet installation is proper,

neither gas nor liquid will be able to escape by the upset end of the

rivet. This is a dry, metal-to-metal seal - the best seal known -

achieved without the aid of chemical sealants. This is the theory for

rivet orientation in sealed areas and is the basis for the NACA rivet

method (see Figure 51).

Upset all protruding head rivets at sealed boundary areas in such a

way as to locate the maximum swelling in the primary leakage path.

The four views in Figure 52 are typical of laminated joints. Study

each view to get a clear understanding as to how the seal is obtained.

Three fillet seals are necessary to prevent leakage of air or fuel

14·1

NON-SEALED AREA - THIS SIDE OF WEB

MEMBERS LOCATED OUTSIDE OF SEALED AREA

FILLE~"S~AL •• ~~BE:: ':END ::~SlDE OF SEALED AREA

ABSENCE OF FILLET WOULD PERMIT A LEAK PATH AS

SEALED AREA - THIS SIDE OF WEB INDICATED BY THE DASHED LINE

FIGURE 52. CORRECT RIVET ORIENTATION

through the joint seam (leakage at the joint seam would bypss the

upset seal and escape at the rivet head). Each view is described in the

following:

View A: To attach one or more members inside the sealed area to the

skin or web (with no seam leading to the outside and no

member outside the sealed area), upset the rivet outside the

sealed area. Note that this is the only time the rivet is upset

outside the sealed area. All other times, the rivet butt is

located on the pressurized, or in-tank, side.

View B: To attach one or more members inside and one or more

members outside the sealed area (with no seam leading to

the outside), upset the rivet inside the sealed area.

View C: To attach one or more members outside the sealed area

(with no seam leading to the outside), upset the rivet inside

the sealed area.

14-2

View D: Where seams lead to the outside, upset the rivet inside the

sealed area.

Where it is impossible to position rivets properly (see Views B, C, and

D in Figure 53), apply sealant over the manufactured rivet heads.

This practice, however, must not be looked on as a simple solution to sealing all misoriented rivets. It is not only the additional time and

materials that limit this practice, but additional weight is added to the

airplane for its entire lifetime. Aircraft weight is a critical item since

every pound means more fuel consumption and less payload.

Figure 53 is identical to Figure 52 except that all rivets are incor­

rectly oriented. In this case, notice that in order to make each joint

leakproof it would be necessary to apply two additional fillet seals in

View A, and to apply sealant to the six rivet heads in Views B, C,

andD.

NON-SEALED AREA - THIS SIDE OF WEB

0 .. °"'7 ® ® ~. £3]ID; Qffi; ~ SEALED AREA-THIS SIDE OF WEB

DOTTED LINES INDICATE POSSIBLE LEAK PATHS

FIGURE 53. INCORRECT RIVET ORIENTATION

14·3

If DASH PAGE REVISION DASH PAGE REVISION 0_ METHOD METHOD

~J NO. NO. U:T. DAft NO. NO. lU. DAn:

~ MtTHOD-ItIV£T II SCRr_ HOLE PREPARATION ..• Ie t-I·17 -Z7 COIJHTEftSIIHC fOIt THE 8R,Il ("$14219) TENSION

" 8A 9-30-'~1 HUD R1V!.TS,

TABlE OF CONTENTS. REviSION LUlU RECORD COUNTERSINK rOR T!olE 150' ('000801 SHEAR ·1 " I .. I'··"··~ ~f.

1.0,0,1 Ie t- 1_11 ." HEAD seRlE'" g

TABLE or CONTENn .. REVI$ION lETTER RECORD 1.0.0,2 Ie I-I-It g l' TABt.[ or CONTENTS .. ftEV'S'ON lETT[JII RECORD 1.0.1 Ie 1-1-t7

~l "11 OIU.llrING S'nUIOLI FOR HOLt: PREPAItATIOH ... 10-8-75

!! is DIV •• 'LUSN 1"0111 RIVETS " c: -. PRE-DUIPL! 'Olt ftlVETS AZ I 7-1-11

"Ii: ::u

!I-m -. COMBINATION PIIIE-D'MPL£ a COUNTERSINK rOR Rlv£TS " en eCUHTtRSI'UC fOR 'UV£TS I. 10-15-81 ~ i

-I s:: -. PRt-QUIPl.l' roft ICIU_S .W 11-12-71 g lie:: $~ !!I -, COUIINATION "Rt-OIMPLE Il COUNTERSINI( fOR SCREW! , AW 11-12-11 ~ =g ::z: CouTtltalNt( ,.Olt ,. ... UtI" T£NSlON H£AO SCIUW 10-t-1' l ::9: ~ ~~ 0 -.. COVT£RSI"IC IHAeA1 "OR IUVETS 1-1_71

U CI ,.

~ ~; T"11il ' ... VSN '011: II:IVETS-COUNTlRSH'fI( ONt.or .. AT I-II-IS g .j,. CI

fa:- ::u -.. oaSOUTED • ,,£PLAC£O BY _1 c: ~ l> -IS Ol"Ot.£TID • Itt.PLACtD tv-3

II

i =e

~ z -.. EIIICO IIIIYUS " AT 2:-11-6'

Ci) -IS NON-FLAIH RIYITt AZ 1-1-17

~. en -II ILIHD II:IVITI " 10-1-7' en (;) ·-11 ",ACA SlUiQ; Rlv!fa " AY t-3-1'

'" ~ -II eOM8INATION PIII[-OIWPI..! It. C'suNK FO" HAc A ,!IIyns " AZ 7_ '-77 !.l jJ !il ." . g -It DE-leu DIMPL.E " AT 2:-II~U Z ...

~ ~ ~ -.. COUNTERSINK 'Olt RIVIT HEAD aCIIEWS " AW 11-12-7 I ,.. '" -II PRE-OIWIlt.! 'Olt Iitlvn HUD ICIitE .. S •• Aw 11-12-71 ... ...

-u COMBINATION PIItt-DIMPI..! It. COUNTlRSlNI( '0111

" low 11-12-71 .. IJI

RIVET HUD leU:w. i'l -u eOuHTtRSINIC '0111 IH(AIII HlAo RivETS " AZ 1-1-71

-.. , ... u; ,"vnl CUNCO" .ounn PRoeUt) .. AW 11-12:-11

-II COUIHUI'HIC 'OR "tOUclO HUD IC·It!.1 " AW 1I-lt-11

-II eouHTU~HIC 'Olt THE 11111"211 SHUlit HEAO RiVET " Ie 1-'-11'

SECTION 15 METHOD DRAWING S5076260

15-1. GENERAL

Method Drawing S5076260 (see Figure 54) covers 24 standard

methods for rivet and screw hole preparation. Each of the methods is

identified by a title and dash number. The drawing may be obtained

from Manual Control Files and is subject to revision without notice.

NOTE

It is the responsibility of the user to work to the latest change

letter.

Authorization for the various methods is indicated by the number­

letter code in the southwest quadrant of the drawing symbol. Refer to

Section 11 for an explanation of the coding system used in the draw­

ing symbol.

15·1

ORAWING NO. SOZliZ6Q

G? PAGE NO. 5

_____ ~C:H~A:N:G:E~L~E:T~T~E~R:·::~B:B.:::::: ____ DOUGLAs

TITLE: -4 COUNTERSINK FOR RIVETS (MS20426, MS20427, NAS"991 545794291 S45794'311 -4

DIHENSIONAL LIMITATIONS:

A

[

SHEET THICICH(SS

<1000 iiO> DRAWING

SYMBOL

&I""<"'''''~'"''®'"''~'''"''''''' ::-+-"""'"@<"<"~<"<"~~~'""'""1"""""'" ~ . t CT~

e ?Z 2 Z2 ?2 22 221 Ie?? ?~2 2 ? S!:A: EDGE .010 MAX RADIUS FOR COMBINA noN MACHI NE

C~ D:/COUNTERS'NK OPERATION

~'>~~ .OIOMAX. RAOIllSJ ./

r----r--~F~~~:~~,~:~~~'---r~--"-T-rn--'c-'-.,-S-S~c-OU-.-T'-'-S'-.-" ~ *" MINIHUM DIAMETER ,. A RiVET

SIZE STANDARO JACKETED

1116 .067 .. 032 .095 *NOTE: THE HOLE SIZES .072 .105 SPECIFIED ARE 111£

3/)2 .098 .. 160 SUBJECT OF AN INTCR-.0110 COMPANY AGREEMENT

.103 .110 8ETWEEN OAC AND MeA/ii

118 .1285 .!Jla .2'" AND MAY NOTSE CHANGEl .oso WITHOUT PHIOR INTER-

.1311 .111" .216 COMPANY COORDINATION.

5/32 .161 .171 .06,3 .261 A NOTE: WHEN ATTACHING .166 .17" .217 NUTPLATES AND GANG

)/16 • "192 .202 ~O71

.,3)" CHANNELS ONLY • .198 .205 .3"" INCREASE COUNTERSINK

OIAMETER TO .174· .184 IN

1/' .255 .265 .100 .1157 .050 AND THICKER • 263 .268 •• 61 MATERIAL •

5/16 .317 .125 .5"5 .)2) .555

3/8 .380 .160 .675 .)87 .685

NOTES: I. THIS MeTHOD SHALL 8E USED ONLY IN THE FOLLOWING CONOIT-ION$..

A. WHERE THE SHEET THICKNESS EXCEEDS THE MAXI MUll THICKNESS FOR

DIMPLE IJETHODS. OR ..

B. wHERe DIMPLe MeTHoa OF INSTALLATION IS NOT SPECIFICALLY INDICATEa

ON THE ASSFMBL Y DRAW/NG.

C. SHEET THICKNESS MIN. 032 FOR RIVETS WHEN ATTACHING ANCHOR NUTS.

<. COUNTERSINK DIMENSIONS ARE CHOSEN SO THAT MANUFACTURED RIVET HEAD

WILL BE "FLUSH" TO "HIGH" AFTER DRIVING. THIS MAY N£CESSI TATE

SHAVING DEPENDING UPON SURFACE REOUIREMENTS •

.1. WHEN + OR • ., IS SPECIFIED. SHEETS 8ELOW JON THICKNESS MUST 8£ CSK.

FIGURE 55. COUNTERSINK FOR RIVETS -- 55076260·4

15·2

15-2. COUNTERSINK FOR RIVETS, S5076260-4

The -4 method (see Figure 55) is authorized for use when a "c" or a

"-4" appears in the southwest quadrant of the drawing symbol. This

method is used for hole preparation for 100-degree flush-head rivets:

Countersink is 100 ± 1/2 degrees. The chart provides information for

(a 3/16-inch-diameter rivet is used as an example):

Final Hole Size: 0.192 to 0.198 inch for a 3/16-inch standard rivet.

Minimum Sheet Thickness (for countersinking): 0.071. Do not

countersink material thinner than 0.071 inch for a 3/16-inch rivet

unless Note 3 on the -4 drawing is applicable.

Countersink Diameter: 0.334 to 0.344 inch. Note 2 on the -4 draw­

ing specifies that rivet heads will be "flush" to "high" after

driving.

15-3

POSSIBLE LEAKS ARE STOPPED BY RIVET HEAD

I HEAD IS MILLED TO MEET SURFACE i HEIGHT REQUIREMENTS

'--~~-7-=*"t ~....,

VIEW A

COUNTERSINK DIAMETERS ARE CALCULATED SO THAT MANUFACTURED RIVET HEADS WILL BE 'FLUSH' TO 'HIGH,' NEVER LOW. RIVET GUN VIBRATION PACKS (CONCENTRATES) THE RIVET HEAD INTO THE COUNTERSINK.

CORRECT INSTALLATION OF FLUSH HEAD RIVET

MILLABLE DEPTH . ,..--COUNTERSINK DIAMETER IS LESS THAN THE l ~ MiNIMUM REQUIREMENT

I f ( ~ HEAD DIAMETER, AFTER MILLING. TO SURFACE HEIGHT REQUIREMENT, EXCEEDS THE 5% REDUCTION LIMITATION

VIEW B COUNTERSINK IS TOO SMALL

VIEW C COUNTERSINK IS TOO LARGE

BUCKING BAR PUSHES SUB-SURFACED RIVET HEAD AGAINST THE RIVET SET AND FLUSH WITH THE MATERIAL SURFACE

FIGURE 56. COUNTERSINK WIDTH FOR FLUSH HEAD RIVETS

15-4

It is important that countersink dimensions are within the specifica­

tion. Fuselage skins are usually attached to longerons and station

frames by this method. Since rivet heads are flush on the outside skin

surface, and therefore no option is possible for rivet orientation, the

hole seal must be obtained at and by the manufactured head. View A

of Figure 56 shows how the hole seal is achieved, providing that the

hole and countersink width conform to the method drawing.

If the countersink width is less than the minimum specified (see

View B, Figure 56), too much of the rivet head will be removed by the

milling process. This results in a tension loss that may be prohibitive.

The head diameter of flush rivets must not be reduced over 5 percent

by the milling process (reference DPS 3.621).

If the countersink width is more than the maximum specified (see

View C, Figure 56), the head will not fill the countersink, and leak

paths will be created for fuel or air pressurized areas.

If any portion of the countersink is visible after riveting, it is not acceptable. The head should not be swelled to hide the countersink,

since a void will exist below the surface of the head.

15·5

DRAWING NO.-25l!O!...72.62"'6"!O"-___ _

______________ DOVO~ PAGE NO._...:4:-______ _

CHANGE LETTER AI!

TITLE: -J COMBINATION PRE-DIMPLE AND COUNTERSINK FOR RIVETS OBtENSIONAL II HIT AT IONS: (MS2042G, MS20427, NASI199

1

S4579429, S45794St)

OUTER SHEET

~H I

HIDOl( SHEff (OR SIf££TS) (MAY Oil HAY' MOT BE

PREStMT - SEE HOT( ))

Hilt Sti((T TH'C1.~£SS7

f.R <S'" ]

" ~,~~ NOT£: rHE IIOL£ SIZeS SPErIFJ£O AII£ TH£ SlIe"Err OF AN

INTERCOMPANY AGREEMENT BETWEEN OAC AND MC AIR AND MAY NOT 8£ CHANGED WITHOI.IT PRIOR INTERCOMPANY COORDINATION.

DRAWINQ SYHBOL

+ -3

11==::::::~ I L-e~~~~1 -3 O!~l~~r It===::~ I f \

OTH(lhfIS( I SPECIFIED ( Jig

. I -34 _)~~~ ! 0=, ur- (SEE 'OTE}) L ____ J.J ~ I

~ ~-~!~ L~~?'D£ ~~E,~~;::~,.PU" I

.IV1:T -,* Sttl: OI~U(lll

1". ... , .OT2

:t/u ,0 •• .10S .1U!J • U"

slu • 161 .16(-• t •• ... .,,' .".1 ::!,

.o,t'

.... ...... 0171 .I'U 0, .lO, '-.

.117

.U7

. ~4' ." . .471 .... , .... .S>

NOTES: I. FOR ATTACHMENT OF ANCHOR NUTS (USE .1/.12 RIVETS ONLY}. DIMPLE OUTER SHEErS

I.IP TO AND INCLUDING .025 AND COUNTERSINI( OUTER SHEETS .0.32 AND OVER,

2. IIIDOLE SHEET (OR SHEETS} MAY 8E PR£~DIl/PL£D PER ~2 IF SHEET DOES NOT £).'C££O

MAX THICKNESS FOR DIMPLING. IIIDDLE SHEET NEXT TO DIMPLE MAY BE CSUNK IF

SHEET IS "'IN THICKNESS FOR CSK. UNLESS OTHERWISE SPECIFIED BY OWG SYMBOL.

3, COUNTERSINKING or MIDDLE SHEET (OR SHEErSI BELOW MIN THICKNt::SS IS NOT PER. MITTEO UNLESS DC OR w.JA IS SPECIFIED

4. WHEN O~C OR -38 IS SPECIFIED. MIDDLE SHEET OR SHEETS /JUST 8£ OIl/PLED.

So GAP BE TWEEN SHE£ TS TO BE AS SHOWN FOR • Z ME THaD.

FIGURE 57. COMBINATION PRE·DIMPLE AND COUNTERSINK FOR RIVETS

MeOonneIi Douctas Corpor.tion Proprietary 1nf00000ion - Use or disclosure of 1his information is subject to the restriction on the title page or on the first page of this document.

15-6

15-3. COMBINATION PRE-DIMPLE AND COUNTERSINK

FOR RIVETS, S5076260-3

The -3 method is used. when the drawing symbol code specifies DC,

D2C, -3, -3A, or -3B. Figure 57 shows various types of joints. The -3

method consists of a dimple nested into a countersink, and is used

when the outer sheet(s) is too thin for countersinking and the inner

structure is too thick for dimpling. Notice that the countersink

diameter for a 3/16-inch rivet is 0.349 to 0.359 inch, while the -4

method specifies 0.334 to 0.344 inch for the same size rivet. The -3

method (larger countersink) would allow a rivet head to seat below

the surface. However, the -3 countersink is not for a rivet, but to

accommodate a dimple. The inner side of a dimple is always wider

than the outer; therefore, the nesting countersink must be larger

than the fastener head to prevent a gap (see Figure 58). Do not use a

fastener head to determine countersink widths; use the micrometer­

type countersink gages for accuracy. The minimum sheet thickness

for a 3/16-inch rivet is 0.080 inch. Since the countersink for the -3

method is wider than in the -4 method (minimum sheet thickness:

0.071 inch) the material must be thicker.

MAXIMUM MATERIAL THICKNESS I" '" DIMPLE WIDTH ON FLUSH SIDE

MINIMU' MATERIA~ <1- (LOWE'! PORTION OF DIMPLE IS WIDER THAN flUSH THICKNESS q , SIDE. COUNTERSINK WIDTH TO ACCOMMODATE DIMPLE

~COUNTERSINK PER -3 METHOD

~- HOLE DIAMETER

FIGURE 58. DIMPLE WIDTH DETERMINES COUNTERSINK WIDTH

15·7

DRAWING NO. ~.",0C!.7.",t,-,.",0,--__ _

~ PAGE NO._--'2"'2'-____ _

___ ~~:A:N~G:E~L~ET~T~ER::A=C::::::::::= ____ DOUGLAS

TITLE:

NOTES:

-23 COUNTERSINK FOR SHEAR HEAD RIVETS (NASI097 23 54579428, 54579430-N,4SI200, RV5928 J

uZZZZZZI PIZZZZZZ3

RIVET HOLE SHEET THICKNESS COUNTERSINK SIZE DlA* MINIMUM alA

.098 .135 3/32 .103 .032 .140

118 .1285

.040 .175

.134 .185

.!3i .161 .0.0

.226 .... .236

3116 .192: .283 .19. .06' .293

1/4 .255 .071

.376 .265 .386

DRAWING SYMBOL

-zi-

I. COUNTERSINK DIMENSIONS ARE CHOSEN SO THAT MANUFACTURED RIVET

HEAD WILL BE "FLUSH TO HIGH" AFTER DRIVING, THIS MAY NECESSITATE SHAVING DEPENDING UPON SURFACE REOUIREMENTS.

2. WHE"!n/- OR - 23 IS SPECIFIED. SHEETS 8ELOW MIN. THICKNESS

MUST 8£ COUNTERSUNK.

*NOTE: THE HOLE SIZES SPECIFIED ARE THE SUBJECT CF AN INTERCOMPANY AGREEMENT BETWEEN DAC AND MC AIR AND MAY NOT BE CHANGED WITHOUT PRIOR INTERCOMPANY COORDINATION.

FIGURE 59. COUNTERSINK FOR SHEAR HEAD RIVETS, S5076360-23

McDonnell Douclas Corporltion Proprietary Information - Use or disclosure of this information is subject to the restriction on the title page or on the first page of this document.

15·8

15-4. COUNTERSINK FOR SHEAR-HEAD RIVETS, S5076260-23

The -23 method is used for countersinking when flush shear-head

rivets (Figure 59) are specified. If the drawing symbol code specifies

"-23," sheets below the minimum thickness must be countersunk.

The countersink diameter for this particular rivet is frequently a

"controlled countersink" (Engineering specifically calls out by

blueprint an exception to the method drawing). This countersink

diameter is less than the dimensional callout on the method drawing

since the material thickness is unusually thin. To prevent chatter and

to maintain concentric countersinks, the substructure must be in

place while the skin is being countersunk (see Figure (2).

NOTE

For inner-member countersink dimensions in a combination

dimple and countersink joint, refer to DPS 3.67-3.

15·9

T I TL[: -16 BLIND RIVETS:

DIKUSIOMAL LI"ITATIOM$:

PULL STEil RIVETS:

COUNTERSINK AND HOH-FlUSH ST.utOARO SHANK RIVETS

RIVEr FlU!.. HOlE SIZE DIAMETER

)/32 .091 .101

118 .1285 • 1'2

5/)2 .160 .164

)/16 .192 •• 96

COUNTERSINK. OIHFtE & NOH-FLUSH BUlB SHAHK RIVETS

RIVET SIZE FINAL

RJ~;:

'/8

5/n

,/16

DIMPLE STANDARD SHANK FLUSH RIVET

KOlf OIA aTORE DIMPliNG

.Q94

.100

•• 20 .128

.152

.159

COUHTEr.,IH. OIA.

I"01t Fl.USH

&tILa RIVETS

IoH="'=I=NA=L=t==A;,;C=TU=A=L=~~H=OL;,;E,,;O;;;'=A'=I (5££ HoTE I)

I • .11&4 .22.2

~_'_._+-_'_'_' __ -j:._...: . .:." __ 7-1 . 232 .177 .213

~_51_)_2-+ __ .'_7) __ -j~":'':''. __ '-1 .ttS

L-:.:)/.::l,:,,'-L_..:.:.2 __ .1_5 __ ..L-':i.i~~~:.-..J :.!::

CHEIIICALLY EXPANDED RIVETS:

flUS'H AHO MOH flUSH

RIVET SrzE fiNAl HOLE

IIOH I IU.l ACTUAl DIAMETER

,18 .1:). .1}S .139

5/:)2 ~171 .172 .176

)/16 .202 .20) .207

DRAwING NO. __ --=S:;o;,.76::;.~6:;:O:._._ PA"E. NO ____ ~/5~ __ _

CHANGE LETTER· AY

-16

DIMPlE OVERSIZE SHAHK flUSH RIVET

FINAL HOLE OIA ~~~!i . Hoi!""'iA

.1285

.1;32 .1'~ .1)7 .141

.160-

.16 • .112 .117

.18' .192 .196

.20, .205 .209

NOTES: 2. ~rJlttf'!r/I/-:'Jfr~.AND GAGE L IMI TATICNS ARE PER ~4 AfETHOO. EXCEPT

3. DIJJPL£ DIAMETERS ANO G.46E LlAfI TAT/CNS ARE PER -2 IlElHOO.

4. IIH&I OII.lPt..£S ARE USED. FINAl.. HOLE DIAJlETERS ARE {)fIILL£[) AFTER OIJJPL./NG.

5. INSTALL PER CPS J.67.

FIGURE 60. BLIND RIVETS - 55076260·16

McDonnell Dougtas Corporation Proprietary Information - Use or disclosure of this information is . suPiect to the restriction on the titre page or on the first page of this document.

15-10

15-5. BLIND RIVETS, S5076260-16

The -16 method specifies hole sizes, dimpling, and countersinking

requirements for various types of blind rivets (see Figure 60).

15-11

pRAWING NO. 5076260

_____________________________ ~UG~ PAGE NO. ,

CHANGE lETTER AT

TITLE: .. /0 COUNTERSINK (NACAJ FOR RIVErs -/0 DIHElISIDHAl LIMIT'TiOKS:

>;SS" 5S5SSS S1 ISS\SSSSSSS\

PROTRUDIKG HEAD FLUSH HEAO

I«<~{@ O"VI'G~ .,"",cru'£o SYHBOl. RiVET HEAD (REF)

ssi HOLE 01 AM(T£R SHEET

RIVET COUNTERSINK THICKNESS

SIZE STANOARD *" JAClETEO MINIMUM OUMETER

1/16 ,061 .025 .!OO .ou .100

3/32 .098 .0,)2 .136 .103 .1"6

,/8 .1285 ., .. .0110 .1S11

.131l .1111 ' . • 19Z1

SIJ2 .161 .171 .... .231 .166 .17 • .2/11

)/16 . In .202 .06) .283 .198 .205 .29)

,I, .255 .265 .090 .)95 .263 .268 •• 05

5116 .311 .100 .1t55

.)23 .1165

NOTCS:

I, RIvEr IS UPSET INTO THE COUNTERSINK ANO I,/UST 8£ SHAVED ':fH£R£ FLUSHNESS IS REOUIREO.

2. TI~/S AIETHoa WHEN SP~CIFI£O J,lAY BE USED IN COUIJlNAT/ON WITH .j ... 40;1

-15 U£THODS SPEC/FIEO FOR THt. MFO HEAD f..NO OF THE RIVEr.

*Nor£: rHE HOLE SIZeS SPECIFIED ARE THE SUBJECT OF AN INTERCOMPANY AGREEMENT BETWEEN OAe AND "'CAIN AND MAY NOT BE CHANGED w'rHovr PRIOR INTERCOMPANY COORDINATION

FIGURE 61. COUNTERSINK (NACA) FOR RIVETS - S507626()"10 McDonnell DoucIas Corporation PToprietary Information - Use or disclosure of this information is subjes;t to the restriction on the title page or on the first page of this document.

15·12

15-6. COUNTERSINK (NACA) FOR RIVETS, S5076260-10

This NACA (National Advisory Committee for Aeronautics) counter­

sink for rivets method (Figure 61) was developed to obtain a dry,

metal-to-metal seal for rivet holes in integral wing fuel tanks. An ad­

ditional objective was to maintain the strength of a conventionally

riveted joint.

The angle of countersink for the -10 method is 82 ± 1 degrees. Most

flush-manufactured rivet heads require a 100-degree countersink. It is advisable to always check the degree of the countersink cutter that

is to be used. Failure to be cautious has often resulted in salvage prob­

lems, rework, or scrap.

Protruding rivet-head shanks or flush-head shanks are upset into the

82-degree countersink, as illustrated in Figure 61. If a flush-head

rivet is installed per the NACA method, the exterior side will be an

82-degree countersink, and the manufactured-head side will be a

100-degree countersink. See Figure 61 for the drawing symbol

callout, and Section 11 for an explanation of the code.

15-13

ORAY!'ING NO. _-,5,-,O"7-,6,-,2,-,6",,O~ __

~ PAGE NO. __ -"'7'-_____ _

____ :C~H~A~NG~E~L~E~T~T~E:R~:A~&~:::::::: DOUGII;.AS

TITLE: -18 COI.I8INATION PRE .lJIIJPLE IWO COUNTERSINK FOR N~A RIVETS -18 DIHEMSIOMll lIHlTlTlOMS:

flUSH MEAD

DRAVUG 3YH80L

COOlie FOR MfO H(AO-_Dcl~ COOI:~"~; U~(;(.O.../~~ •. " •. " ~ flUH8(R OF DUnR SH(£.TS TO 8E OIHI'LED HOST e£ SP{ClflEI) IF NO OR MORE, I.£. D2C, o,e.

*NOTc'- THE HOLE SIZES SPECIFIED ARE THE RIV(T HOl( SIZE fiNAL HOLE SI.J/JJ£cr OF' AN INTER- Sll£. SEFOR£. * OIAR'~~~~£.T~ COMPANY AGREEMENT OIHf'lIHC

BETWEEN OAC AND .098 MCAIR AND MAY NOT )in 8E CHAHGED WITHOuT .10;1

PRIOR INTERCOMPANY I/e .128$ .1110 CIXJRDINArtON_ .1)" .1114

5/32 .161 .171 .166 .174

UPPER OIMPU 0 ..

+.oe)2, -.0011

.1~0

.19S

.2110

ouT£.R' SH£.U OR SHU TS

PROTRUDING HEAD

OR~VI"Q 3Y"SOL

~ I COOIHO rOR UPS(T (WO

LOWER DIMPLE T 0 .. MAX +.00_. -.002

.15S .025

.205 .0,32

.259 .01l0

NOTES: I. FOR us£ WHeRE Oll/PLE IS REOUIRED ON UPSET END OF NACA RIVErs.

z. RIVEr IS UPSET INro DIMPLE ANO MUST 8£ SHAVED WHERE FLUSHNESS IS

REOUIRED.

J. THIS METHOD WHEN SPECIFIED MAY'BE USED IN COIIBINATION WITH -.). -4 OR

·15 ,IIErHOD$ SPECIFIED FOR THE "'FO HEAO END OF THE RIVET.

4. CAP BETWeeN SHEETS WILL 8£ .000S TO .012.

FIGURE 62. COMBINATION DIMPLE AND COUNTERSINK FOR

NACA RIVETS -- 55076260·18 McDonnell DoucIa Corporation Proprietary Information - Use or disclosure of this information is subject to the restriction on the title page or on the first page of this document,

15-14

15-7. NACA COMBINATION PRE-DIMPLE AND COUNTERSINK FOR NACA RIVETS, S5076260-18

The -18 method (Figure 62) is used when a combination dimple and

countersink is required for the NACA method of rivet installation.

The -18 method provides specifications for the material to be dimpled

(82 degrees) and the -10 method is used for countersinking (82

degrees).

The upset head (butt) is installed in the dimple. The rivet head is

milled (shaved) to aerodynamic tolerances that are applicable to that

particular section of the aircraft.

15·15

DRAWING NO._-"-50"-7!-'6~2"'6"'O ___ _

___________________________ ~UG~ PAGE NO. ______ .-!1.:::6 ____ _

CHANGE LETTER AV

TITLE: -17 HAC" SLUG R I VETS -17 DIHEMSIDIIAl lIHITATIONS:

res'.I. ~ VIEW A ULARG(O

I

I I UPSET HEAO (REr) I ,-

-'-SLOG RIY(T (REF)

RiVET HOLE OIAHET£R $tI(Er COUNTERS I XI(

SllE: STANDARD JACIt£T(O TKICIUIESS '1' M" 1/8 .128 .'>0 .16" .010

.1)1 .tTt .020

51,2 .IS9 .111 .06, .111 .015 .162 .11' .221 . .,0

'/16 .191 .202 .080 .263 .020 .190 .20' .273 .040

1/_ .m, .265 .'2$ .J1S .020 .256 .268 .}O' ....

5/16 . ,,.

.160 .4J5 .020 .,.111 .US .0cO

NOTES: I •. USE HOLES IN ·STANDARO· COLi/MN FOR $-/456832, $-/458448 ANO NASIJ2/

Z. USE HOLES IN "JACKETED" COLUMN FOR $-1.//9869 RIVETS.

FIGURE 63. NACA SLUG RIVETS -- 55076260-17

McDonnell OoucfIis Corporation Proprieb;ry Inforrrmion - Use or d!sclosure of this information is subject to the restriction.on the title page or on the first page of thiS document.

15-16

15·8. NACA SLUG RIVETS, S5076260·17

The -17 method (Figure 63) is used for drivematic-installed slug rivets

and uses the NACA sealing principle. The countersink is 82 degrees,

but the width dimension is slightly smaller than for the -10 method.

The countersink configuration has a radius near the top surface, as

$hown in View A. This improves the seal and reduces chances of

peel-up of the very thin edges of the shaved head due to air velocity

during flight. This occurs if the rivet upset is excessively wide when

bucked into a -10 method countersink.

15·17

DRAWING NO. 5076260 r/ PAGE NO. __ -"-_____ _

______________ DOUG~ __ ~C~H~A~N::GE:...:L::E~T~T::ER~:A~Y=====

TITlE: -8 COUNTERS INK FOR FLUSH TE:NSION HE:AO SCRE:W -8 OtHEHSIOH.ll lIHITATIONS: BREAK EDCE SCREw SiZE 110 ANO ABOVE

:gi~ X 60°845[0 0Ii NOH 0'" OR

NO TcS:

:g~g R RASEO OH HOM OIA

£>..:'-"...::.....:....::.J-4:-J.:::..:>+>..:::.~...::JiOUTE. SHEET THICKNESS

1\:\\\\$1 bSS\\\'I

SCREW NOH 1 HOU: COUKTER5UIIK OUTER COUltT(RSIHK --t,~ SHEET TIfICKKESS o "M(T(R SIZE OIA I Q'AH(TER MIHIHU,",

·'~2 .128 .06,) .220 .1)5 .2)0 .025

.159 .071 .283 ~ .166 ."~-

.166 .060

.)}) .17,) .)11.) A

10 .190 ,190 .O<}O .)8'

'" .)96

1/. .250 .250 .125 .507 .2511 .517

5/16 .J12 .3IZ" .160 .6)5 .316S ,US

.)7:) .37~ .162 .".~ ,I. .)79 .186 .711 .0)0

.<tJ7S .... I 1116 • 4)1

.<'l42S .200 .... I • 500 1.01 • I!> • soo .505

.22_ 1.02' A

9/16 .562 .".25 .258 .1.1.115 UJllESS OTK(R'WISE SPECIFIED ,5675 1.155 0" (/IIG,JI((R,IC DRAWiNG OR

51. • 625 .615 ., .. 1.212 CAllOOT Of It SPEC IFle O.".S • .6,0 1.281

OUVIMa SY"IOL

+ I. COUNTERS/NX DIMENSIONS ARE CHOSEN SO THAT THE SCREW HEAO WILL 8£

"FLUSH" TO "LOW"'.

2. "fH£N c1- OR -8 IS SPECIFIED. SHEETS B£LOW IJIN THICKNESS MUST BE CSK.

FIGURE 64. COUNTERSINK FOR SCREWS - S5076260·8

McDonnell ~$ Corporation Propriet.ry InfOflNtion - Use or disclosure of this information is ~bjectJo the restriction on the title page or on the first page of this document.

15-18

15-9. COUNTERSINK FOR SCREWS, S5076260-8

The -8 method (Figure 64) is used to countersink for standard screw

heads when "c" or "-8" is specified. Dime:p.sional callouts for hole

sizes, per this method, are used only when not specified by the

engineering drawing or a specific DPS. The countersink dimensions

have an overall tolerance of 0.010 and are chosen so that screw heads

will be flush to low. A screw head fabricated to its maximum tolerance

will seat flush in a minimum-width countersink. This meets strength

and aerodynamic requirements and also lessens moisture entrapment

and resulting corrosion in the moat area (see Figure 65). Stop

countersinks should be adjusted near the minimum rather than the

maximum specified countersink width allowed. It is not acceptable

for screw heads to protrude above the surface of the material, since

this creates parasitic drag during flight and thereby increases fuel

usage.

The bottom edge of the countersink must be broken (see View A,

Figure 64) to permit the screw-head-fillet to nest into the radius or

SCREW HEAD IS FLUSH

MINIMUM TOLERANCE COUNTERSINK MAXIMUM TOLERANCE COUNTERSINK

FIGURE 65. ACCEPTABLE SCREW HEAD HEIGHTS

15-19

DRAWING NO. 5076260 __

/ _______________ DOUG~

PAGE NO. ______ '_9 __ _

CHANGE LETTER AW

TITLE: ·20 COUNTERSINK FOR RIVET HcAD SCREwS (.s~4619:JO.]. 4, S. 6, 7. 8)

DIMENSIONAL lIMITATIOHS: -20

SCREW SIZE

10

1/'

5/16

J/3

7116

1/'

DRAWING SYH8Dl

NI'" Oil

.190

.250

.312

.315

.1131

.500

BREAK EDGE SCRE.W SIZE 110 AHI} ABOvE

:~}~ X 60-8A5(0 Oti HOH OIA OR

:gi~ R BASCO ON NOH OIA

[1/2/7/71 PIZZZZZ/ll

COUMHRSUHK ourER COUHT(RSIItK HOll: SHEET THICKNESS OIAMETER

OIAMETER MI"IHUH

f~ .190 .080 .3~1 .1'. .J61 .250 .112 ,1180 ,075 • 2~1t .1!.90

,'In .125 .568 .31.'

:~~:-·315 .160 .)19 .106 A .4l1~ .1BM .BI&l ."4~' .851 .:"00 .2118

.960 .50S .970

* • UNLESS OTHERWISE SPECIfiED

OM £HGINEERI"G OitA-WING OR CALlouT OF It SPECIFIC D.P.S. 'O'O'~ .0)0

I

I A

NOTES: I, COUNTERSINK DIMeNSIONS ARE CHOSeN so THAT THE SCREw HEAD /ifILL 8£

"FLUSH" TO *LOw*,

2. WHEN ---- I -- OR -20 IS SPECIFIED. SHEETS BELOW MINIMUM THICKNESS -~

MUS T BE COUN TERSUNX.

FIGURE 66. COUNTERSINK FOR RIVET HEAD SCREWS

McDonnell Douglas CorporatIOn Proprietary Information - Use or disclosure of this information is subject to the restriction on the title page or on the first page of thiS document.

15-20

chamfer. This eliminates interference and a resulting gap between

the screw head and the countersink. Refer to 8ection 16 for further

details on breaking hole edges.

15-10. COUNTERSINK FOR RIVET HEAD SCREWS, S5076260-20

The -20 method (Figure 66) is similar to the -8 method (countersink for

screws); the countersink width is less to compensate for the smaller

flush head on the Douglas special bolt, 84619303 (3/16 inch) through

84619308 (1/2 inch). This bolt has shear values equal to the tension­

head bolt (-8 method) but less tension load capability. Engineering

specifies this weight-saving bolt when load factors permit.

15-21

DRAWING NO. ~076260

~ PAGE NO. _-'7'-_____ _

___ :CH~A~N~G:E::L~En<~~R~A~W:::::::::: DOUGLAS _

TITLE: -7 COMBINATION PRE-OIUPLE AND COUNTERSINK FOR SCREWS -7 OIMEHSIOHAl 1IIHTATIOHS: 1=-===::1 I ,-f::=~~~l

t====~~ I r \ . L__ \~~~::,:f£T ~l(P£'_5

I "'DOLE SHEET (OR StiE(fS)

£'" SHUT THICICH[SS (HAY OR HAY loT BE

rOR CS 1111( t P'R(stttr SH JiIOT( ~) F==.JI g ~)!El !~ I

MPf $H((T COUIIT£RSIU HOLE rHICkNESS OIAH£T(R SCREW

SIZ( DI.lMHU fOj:t COUHTERSll'lk

I HOC< I rOIAI 10

1/.

5/16

,I.

.128

.lJ~

.1:59

.166

.166

.17)

.1'0 . I,.

.250

.'54

.11U

.:UCO

.'75 .,79

.OJ,O .215 • UNLESS OTH(R_ .225 WiSE SPEC IF' 1(0

.06) .28) OM (ltGIMHRIItG .29) ORAW'"G 05r .n) CALLOUT OF A

• 080 •• 34) SPECIFIC O.P.S •

.09<) .}86 .)96

.513 .12!J, .!l1J

.160 .8)9 .6119

.lS8 .767 .117

NOTCS: I. COUNTERSINKING 0' IIIDOLE SHEET (OR SHEETS) BELOW /,lIN rHICI<NESS IS NOT

PERlilTrED UNLESS DC OR .. 1A IS SP£CIFIEO

2. WHEN Di.2...JlL:MJulC OR ·78 IS SPECIFIED. MIDDLE SHEEr OR SHEETS MUST BE DIMPLED.

J. "'.IDDL..£ SHEET lOR SHEErS) J/AY 8£ PRE-DIMPLED PER -5 IF SHEET OO£S NOT EXCEED

"AX THICXNESS FOR OIMPL INt;. J/IDDLE SHEET NEXT TO DIIIPLE MAY BE COUNTER ..

SUNK IF SHEET IS MIN THICKNESS FOR COUNTERSINK. UNLESS OTHERwISE SPECIFIED

BY DRAWING SYM/JOL.

4. DIMPLING OF cXTRUSION IS NOT PERMITTED EXCEPT WHERE SPECIFICALLY INOICATEO

ON THE ENGINEERING DRAWING.

S. GAP BETWEEN SHEErs TO 8£ AS SHOWN FOR -5 'uE(HOO.

FIGURE 67. COMBINATION PRE-DIMPLE AND COUNTERSINK FOR SCREWS McDonnell Douglas Corporation Proprietlry Information - Use or disclosure of this information is -subject to the restriction on the title page or on the first page of this document.

15-22

15-11. COMBINATION PRE-DIMPLE AND COUNTERSINK FOR SCREWS, S5076260-7

The -7 method (Figure 67) consists of dimpling the outer sheet(s) and

nesting the dimple(s) into a countersink. It is for standard-tension

screw heads and must be used when the drawing symbol code calls out

a -7, -7A, -7B, or D2C, D3C, etc.

This combination method is used when the flush side material is too

thin to countersink per the -8 method (see Figure 64).

The -7 countersink widths are wider than in the -8 method since they

must accommodate the protrusion side of the dimple. Otherwise, a

gap will occur at the juncture of the countersink and the dimple.

If -7 A or DC is specified, countersinking below the minimum sheet

thickness is permitted (see Section 12-3 and DPS 3.67-3).

The callouts for hole sizes are not to be used if specified otherwise on

the engineering drawing or applicable DPS.

After the drilling operation is completed, the material to be dimpled is

removed. However, it is important that the other sheets are held in

accurate alignment with the proper clamping devices. This is an

essential setup, since the countersink cutter will enlarge the hole in

the top material that normally is too thin for countersinking.

15-23

Hole expansion is done only after the final heat treat and the straight­

ening operations have been completed.

Prior to expansion, holes must be prepared as follows (reference

DPS 3.67-25):

a. Ream holes to proper size.

b. Deburr holes, but do not chamfer hole edge. Remove only the

ridges protruding above the surface; use No. 240 or finer

abrasive paper.

NOTE

Do not use a countersink cutter for deburring.

After expansion, if burrs protrude above the surface (see Figure 105),

remove them by hand with No. 240 abrasive paper or finer. A

chamfered hole edge is not acceptable.

NOTE THE HOUR-GLASS ,REMOVE THESE BURRS BUT DO

HO_~A

FIGURE 105. EXPANDED HOLE - CROSS·SECTION VIEW

22-2

A water-dampened cloth (not dripping wet) shall be used to wipe off

all lubricant residue adjacent to or inside expanded holes. Wipe dry

with a clean cloth.

22-2. QUALITY REQUIREMENTS

Hole expansion must be performed by certified personnel only.

To obtain the maximum fatigue life improvement, it is important that

the holes meet the diameter requirements, as specified in the DPS,

before and after expansion.

Any holes that have been redrilled and rereamed to achieve the mini­

mum size after the hole has been expanded are not acceptable and

must be submitted to Liaison Engineering.

After expanding, the hole and the adjacent area must be free from

cracks. Detail parts in fabrication departments must be given a fluor­

escent penetrant inspection for cracks.

Work performed in assembly departments must be visually inspected

with a magnifying glass of five power or better.

22-3

BEARING AREA

BROACH

BROACHED

CHAMFER

CHATTER MARKS

GLOSSARY

The contact area between two surfaces

that are forced against each other.

A tapered, multitoothed tool used to pro­

duce holes of close dimensional toler­

ances with a fine hole wall finish. The

broach is pulled through a previously

made pilot hole.

A term used to describe a discrepant

condition that occurs when a clearance

fit fastener is forced into an undersize or

misaligned hole. This malpractice tears,

enlarges, elongates, and threads the

hole.

A slanted or beveled edge.

Uneven or irregular-shaped cuts on a

surface caused by cutting tool vibration.

G-1

CHUCKING

CHUCK RUNOUT

CLEARANCE FIT

COINING

The process of installing and tightening

a tool in a chuck. (Eccentric chucking is

off-center installation of a cutting tool in

a chuck.)

Runout or wobble induced into a cutting

tool by the chuck. All chucks contribute

to the runout problem; the degree of run­

out depends on the precision built into

the chuck and wear of the spindle sup­

port bearings.

A nonforce fit that results when a fast­

ener is inserted in a larger mating hole.

The process of prestressing holes, slots,

and edges of doublers with highly accur­

ate dies.

COMPRESSION LOAD External axial forces that are applied on

parts and act toward each other.

CONCENTRIC

COUNTERSINK

A hole and countersink having a com­

moncenter.

G-2

CORROSION

DUCTILE

EDGE DISTANCE

FATIGUE FAILURE

FATIGUE LIFE

The process of oxidation or deterioration of metals, induced by either a direct chemical attack or by an electrochemical process.

Capable of being formed, bent, or

stretched without cracking.

The distance measured from the center of a hole to the edge of the material.

A fracture produced by repeated, alter­

nating tension loads induced during

flight or during aircraft operation. Damage first occurs on a submicroscopic scale, the material cracks, and pro­

gressively deteriorates until final rup­

ture.

The number of cycles of fluctuating

stresses of a specified nature that a

material can sustain before failure occurs.

G-3

F AYING SURFACE

FEED RATE

The surface areas of mating parts that

are in contact with one another. The

area between parts where wet sealant is

applied for sealing purposes.

The distance that a hole cutting tool

penetrates the material per each revolu­

tion of a chuck. Feed per revolution

(FPR) is calculated in thousandths of an

inch. Excessive feed or pressure causes

drill-point deflection and vibration;

insufficient feed tends to let the tool idle

and causes discrepant holes.

FRETTING CORROSION Chips and burrs, between mating sur­

faces of metal parts, which when sub­

jected to a slight oscillatory motion

cause abrasion of the surfaces. This

wearing action leaves bare metal sur­

faces, which oxidize rapidly.

GUST LOAD Additional stresses imposed on an air­

plane, especially the wings, as a result of

encountering sudden up or down air cur­

rents.

G-4

HEAT INDUCTION

HOLE TOLERANCE

INTEGRAL PILOT

Heat that is generated and induced into

materials during the drilling operation.

The heat should not exceed touch temp­

erature for stainless steels, titanium,

and aluminum alloys since it causes a

loss of mechanical properties and corro­

sion resistance.

The permissible overall variation bet­

ween the minimum and maximum hole

size as specified by Engineering.

A nonremovable guide that is part of a

countersink cutter. The proper size pilot

provides assurance of concentric

countersinks. Two types are available,

each having a definite and specific pur­

pose: (1) with a built-in radius and

(2) without the built-in radius.

INTERFERENCE FIT The hole size is smaller than the mini­

mum fastener diameter. The fastener is

forced into the hole, permitting uniform

loading of each fastener for shear

stresses.

G-5

MALANGULARITY

NOMINAL

NOTCH PATTERN

PRELOAD

REAM

A condition where holes are other than

perpendicular to a surface or other than

90 degrees to the point of tangency on

contoured surfaces.

Mean; as used in this text designates an

average or intermediate between

minimum and maximum dimensions.

Metal surfaces consist of high and low

areas as a result of the tearing and

abrading action of cutting tools. The tool

finish and direction of cutting operation

determines the pattern.

An external force applied during

assembly by the use of clamping devices

or fasteners to forcibly close a gap bet­

ween mating surfaces. The result is an

assembly built with detrimental, sus­

tained stresses that were not calculated

in the design and may cause premature

failure of the joint.

To enlarge a predrilled hole with a

reamer. Reamers are used for holes hav­

ing a tolerance of 0.002 inch or less. G·6

RESIDUAL STRESS

RUNOUT

SHEAR STRESS

STRESS

STRESS RISERS

STRIATION

Internal or locked-in stresses induced

by manufacturing processes such as

machining, fabricating, and heat

treating.

Inherent wobble at the cutting lip of a

drill or reamer; axis of the cutting lip is

off-center to the axis of the drill shank.

External loads that tend to slide one

structural part over the surface of

another in opposite directions. This

force tends to cut or shear the fastener.

Externally applied loads that are

resisted by the internal strength of a

body. There are many types of stresses,

which are identified by the direction of

the applied loads.

Surface irregularities such as scratches,

nicks, gouges, tool marks, and notch pat­

terns that reduce the fatigue life.

A very small parallel groove.

G-7

TENSION STRESS External forces or loads that tend to

increase the length of a body.

TORSIONAL RIGIDITY The degree of resistance of hole-cutting

tools to a twisting load (torque and feed).

For example, short drills with large

diameters have a high resistance to tor­

sional rigidity, while, conversely, long

drills with small diameters have a lower

resistance.

WOODPECKERING The act of intermittently removing a

drill from the hole to facilitate chip

removal, especially in deep drilling. This

practice is to be avoided during the final

sizing step for holes having a tolerance

of 0.003 inch or less.

G-8