ansi asme b.1.20.1
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ANSI-ASME B.1.20.1TRANSCRIPT
A N A M E R I C A N N A T I O N A L S T A N D A R D
ASME B1.20.1-2013[Revision of ASME B1.20.1-1983 (R2006)]
Pipe Threads, General Purpose (Inch)
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ASME B1.20.1-2013[Revision of ASME B1.20.1-1983 (R2006)]
Pipe Threads,General Purpose(Inch)
A N A M E R I C A N N A T I O N A L S T A N D A R D
Two Park Avenue • New York, NY • 10016 USA
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Date of Issuance: November 15, 2013
This Standard will be revised when the Society approves the issuance of a new edition. There willbe no written interpretations of the requirements of this Standard issued to this edition.
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The American Society of Mechanical EngineersTwo Park Avenue, New York, NY 10016-5990
Copyright © 2013 byTHE AMERICAN SOCIETY OF MECHANICAL ENGINEERS
All rights reservedPrinted in U.S.A.
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CONTENTS
Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ivCommittee Roster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vCorrespondence With the B1 Committee . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2 American National Standard Pipe Thread Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
3 Specification for Taper Pipe Threads, NPT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4 Specifications for Internal Straight Threads in Pipe Couplings, NPSC . . . . . . . . . . . . . . . . . . 13
5 Specifications for Railing Joint Taper Pipe Threads, NPTR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6 Specifications for Straight Pipe Threads for Mechanical Joints; NPSM, NPSL . . . . . . . . . . . 16
7 Gages and Gage Tolerances for American National Standard Taper PipeThreads, NPT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Figures1 Root, Crest, and Flank Engagement, NPT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Basic Form of American National Standard Taper Pipe Thread, NPT . . . . . . . . . . . . . . . 33 American National Standard Taper Pipe Thread Notation . . . . . . . . . . . . . . . . . . . . . . . . . . 64 Gaging External Taper Threads With L1 Ring Gage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 Gaging of Chamfered Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 Gaging Internal Taper Threads With L1 Plug Gage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 NPT Standard Taper Pipe Thread Plug and Ring Gages . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 Suggested Form of Gage Thread . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Tables1 Limits on Crest and Root Truncation of American National Standard External
and Internal Taper Pipe Threads, NPT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Basic Dimensions of American National Standard Taper Pipe Thread, NPT . . . . . . . . . 83 Tolerances on Taper, Lead, and Angle of Pipe Threads, NPT . . . . . . . . . . . . . . . . . . . . . . . 104 Dimensions, Internal Straight Threads in Pipe Coupling, NPSC . . . . . . . . . . . . . . . . . . . . 145 Dimensions of External and Internal Taper Pipe Threads for Railing
Joints, NPTR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 Dimensions of External and Internal Straight Pipe Threads for Fixtures, NPSM . . . . . 177 Dimensions, External and Internal Straight Pipe Thread for Locknut
Connections, NPSL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 Basic Dimensions of Threaded Gages for American National Standard Taper Pipe
Threads, NPT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 Working Gage Tolerances for American National Standard Taper Pipe
Thread, NPT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2310 Diameter Equivalent of Variation in Half Included Angle of Thread for Tools
and Gages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2511 Diameter Equivalent of Variation in Lead for Tools and Gages . . . . . . . . . . . . . . . . . . . . . 26
Nonmandatory AppendicesA The Turns of Engagement Method of Gaging Product Threads . . . . . . . . . . . . . . . . . . . . . 27B Tap Drill Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28C Thread Types and Corresponding Gages and Gaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
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FOREWORD
In 1973, American National Standards Committee B2, which had formerly been responsible forpipe thread standards, was absorbed by American National Standards Institute (ANSI) StandardsCommittee B1 and reorganized as Subcommittee 20. A complete rewrite of the B2.1-1968 standardon Pipe Threads (Except Dryseal) was undertaken. It was approved and formally designated asan American National Standard on February 4, 1983 and was reaffirmed in 2001 and 2006. Thesystem of numbering, to include metric conversions, is as follows:
ANSI/ASME B1.20.1, Pipe Threads, General Purpose (Inch)ASME B1.20.2M-2006, Pipe Threads, 60°, General Purpose (Metric Translation)These standards, ANSI/ASME B1.20.1 and B1.20.2M, have product thread dimensions and
gaging in the same document. Thread inspection specifies the use of L1 taper thread gages similarto B2.l-1968. In addition, emphasis was given to the requirement that all basic thread designdimensions were to be met within the specified tolerances.
This revision of ANSI/ASME B1.20.1 has both significant and subtle substantive changes tothe 1983 revision. It is more explanatory for the user than the previous revision. Significantchanges are as follows:
(a) An acceptability section has been added, providing a referee method in cases of dispute.This acknowledges the potentially wide but acceptable variation in the prescribed gages andgaging methods.
(b) Figures have been updated with additional information and drawn to be more visuallyexplanatory.
(c) The Turns of Engagement method has been moved to an appendix, due to its inherent gagecorrelation issues. This gaging method may be used when parties agree, but it is no longer anaccepted method within the Standard.
(d) Calculated data have been revised following the rounding rules of B1.30M. This providesa standardized high level of precision in calculation. Some tabulated values changed, but nochanges were deemed significant enough to affect the conformance status of products or gages.These changes are generally beyond the margin of error of the required measurements. NPTR,NPSM, and NPSL thread dimensions were not recalculated as some historical methodology,necessary for computation, was not available.
(e) Guidance for tap drill sizes has been updated to reflect varying manufacturing conditionsand the wider range of available drill sizes. Instead of specifying drill sizes, the Standard nowrefers to the tabulated basic minor diameter of the internal thread as a reference in which to basedrill size choice.
(f) Added are detailed explanations on the effects of coatings on threads, as well as guidancefor precoating size compensation.
(g) The gaging point of reference is moved for external threads having chamfer diameterssmaller than the minor diameter at the small end. This change was made to help ensure adequatethread engagement over a wider range of product thread chamfers. This change is correspondentto the existing treatment of chamfers for internal threads.
(h) The point of reference for checking wear on working gages is changed to basic. Previously,the point of reference was the size at the time of manufacture. This change facilitates the calibrationof gages when the original size at manufacture is not known and standardizes gage sizes atmaximum wear.
(i) Gaging guidance for straight pipe threads has been expanded, including allowing the No-Go to enter up to three turns, mimicking ASME B1.2.
(j) The use of indicating gages has been added as a gaging method.Following the approvals of the Standards Committee and ASME, approval for the new edition
was granted by ANSI on October 15, 2013.All requests for interpretation or suggestions for revisions should be sent to the Secretary,
B1 Committee, The American Society of Mechanical Engineers, Two Park Avenue, New York,NY 10016-5990.
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ASME B1 COMMITTEEStandardization and Unification of Screw Threads
(The following is the roster of the Committee at the time of approval of this Standard.)
STANDARDS COMMITTEE OFFICERS
A. L. Barrows, ChairD. S. George, Vice ChairA. L. Guzman, Secretary
STANDARDS COMMITTEE PERSONNEL
A. L. Barrows, Swanson Tool Manufacturing, Inc.K. Bly, Vermont Thread GageG. A. Cuccio, Capitol Manufacturing Co.R. Dodge, Pennoyer Dodge Co.D. Everrett, National Institute of Standards & TechnologyJ. O. Gehret III, Vermont Thread Gage, LLCD. S. George, Ramco SpecialtiesJ. Gervasi, Kerr Lakeside, Inc.J. Greenslade, Industrial Fastener InstituteA. L. Guzman, The American Society of Mechanical EngineersR. J. Hukari, SPS TechnologiesL. C. Johnson, The Johnson Gage Co.P. A. Larouche, Alternate, The Johnson Gage Co.D. D. Katz, Precision Fittings
SUBCOMMITTEE 20 — PIPE THREADS
D. D. Katz, Chair, Precision FittingsP. A. Larouche, Vice Chair, The Johnson Gage Co.K. Bly, Vermont Thread GageM. Cox, Contributing Member, ConsultantG. A. Cuccio, Capitol Manufacturing Co.R. Dodge, Pennoyer Dodge Co.J. O. Gehret III, Vermont Thread Gage, LLCJ. R. Gervasi, Kerr Lakeside, Inc.J. A. Gruber, Contributing Member, J. A. Gruber & Associates, LLCL. C. Johnson, The Johnson Gage Co.R. P. Knittel, Leitech-U.S. Ltd.
v
R. P. Knittel, Leitech-U.S. Ltd.M. H. McWilliams, PMC Lone StarD. R. Maisch, Alternate, PMC Lone StarD. Miskinis, Kennametal, Inc.D. R. Oas, Seaway Bolt & Specials Corp.J. R. Popovic, Cleveland Speciality Inspection Services, Inc.M. W. Rose, Glastonbury Southern GageE. Schwartz, ConsultantB. F. Sheffler, Dresser-Rand Co.D. Skierski, Contributing Member, Sterling Gage & Calibration, LLCR. D. Strong, Doerken Corp.A. F. Thibodeau, Honorary Member, Swanson Tool Manufacturing,
Inc.C. J. Wilson, Contributing Member, Consultant
X. Li, Contributing Member, China Productivity Center forMachinery Industry
D. R. Maisch, PMC Lone StarM. H. McWilliams, PMC Lone StarD. R. Oas, Seaway Bolt & Specials Corp.J. R. Popovic, Cleveland Speciality Inspection Services, Inc.M. W. Rose, Glastonbury Southern GageA. D. Shepherd, Emuge Corp.D. Skierski, Contributing Member, Sterling Gage & Calibration, LLCA. F. Thibodeau, Contributing Member, Swanson Tool
Manufacturing, Inc.
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CORRESPONDENCE WITH THE B1 COMMITTEE
General. ASME Standards are developed and maintained with the intent to represent theconsensus of concerned interests. As such, users of this Standard may interact with the Committeeby requesting interpretations, proposing revisions, and attending Committee meetings. Corre-spondence should be addressed to:
Secretary, B1 Standards CommitteeThe American Society of Mechanical EngineersTwo Park AvenueNew York, NY 10016-5990
Proposing Revisions. Revisions are made periodically to the Standard to incorporate changesthat appear necessary or desirable, as demonstrated by the experience gained from the applicationof the Standard. Approved revisions will be published periodically.
The Committee welcomes proposals for revisions to this Standard. Such proposals should beas specific as possible, citing the paragraph number(s), the proposed wording, and a detaileddescription of the reasons for the proposal, including any pertinent documentation.
Proposing a Case. Cases may be issued for the purpose of providing alternative rules whenjustified, to permit early implementation of an approved revision when the need is urgent, or toprovide rules not covered by existing provisions. Cases are effective immediately upon ASMEapproval and shall be posted on the ASME Committee Web page.
Request for Cases shall provide a Statement of Need and Background Information. The requestshould identify the Standard, the paragraph, figure or table number(s), and be written as aQuestion and Reply in the same format as existing Cases. Request for Cases should also indicatethe applicable edition(s) of the Standard to which the proposed Case applies.
Attending Committee Meetings. The B1 Standards Committee regularly holds meetings, whichare open to the public. Persons wishing to attend any meeting should contact the Secretary ofthe B1 Standards Committee.
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ASME B1.20.1-2013
Pipe Threads, General Purpose (Inch)
1 INTRODUCTION
1.1 Scope
This Standard covers dimensions and gaging of pipethreads of the following series:
NPTNPSCNPTRNPSMNPSL
1.2 Related Standard
Hose coupling joints are ordinarily made with straightinternal and external loose-fitting threads. There are sev-eral standards of hose threads having various diametersand pitches, one of which is based on the AmericanNational Standard Pipe Thread. By the use of this threadseries, NPSH, it is possible to join small hose couplingsin sizes 1⁄2 to 4, inclusive, to ends of standard pipe havingAmerican National Standard external pipe threads,using a gasket to seal the joint. For dimensions, toler-ances, and gaging, see ASME B1.20.7.
1.3 Thread Designations
1.3.1 The types of pipe threads included in thisStandard are designated by specifying in sequence thenominal pipe size, number of threads per inch, and thethread series symbol as follows:
1⁄8–27 NPT1⁄8–27 NPSC1⁄2–14 NPTR1⁄8–27 NPSM1⁄8–27 NPSLDecimal equivalent notation may be substituted for
fractional pipe sizes. For example
0.125–27 NPT
For left-hand threads, add “LH” to the designation.For example
1⁄8–27 NPT–LH
Designations without “LH” will signify right-handthreads.
1.3.2 Each of these letters in the symbols has signif-icance as follows:
N p National (American) Standard
1
P p PipeT p TaperS p StraightC p CouplingR p Railing Fittings
M p MechanicalL p Locknut
1.4 Sealing (NPT and NPSC Only)
1.4.1 Mating Threads. Mating threads shouldalways contact on the thread flanks. The design toler-ances are such that mating crests and roots may clear,contact, or interfere (see Fig. 1). This joint may not neces-sarily seal, unless a sealant is used.
1.4.2 Sealant. Where pressure-tight, leak-free jointsare required, it is intended that threads conforming tothis Standard be made up wrench-tight with a sealant.To prevent galling during installation, the sealant mayhave lubricating properties.
1.4.3 Tightening Torque. Due to application-specificvariables such as materials, wall thickness, operatingpressures, etc., no guidance is given in this Standardregarding joint-tightening torque. However, jointsshould be tightened beyond the hand-tight engagementposition. Advancing the joint past hand-tight createsinterference between external and internal thread flanks,produces a seal (with the use of a sealant), and helpsprevent loosening of the joint. Overtightening may bedetrimental to the sealing function of the joint.
1.4.4 Other Considerations. Out-of-roundness ofmating parts can negatively affect their ability to sealwhen made up wrench tight. The product’s elasticityand ductility will also affect sealing.
1.4.5 Pressure-Tight Threads Without Sealant. Pipethreads designed for pressure-tight joints that may beused without sealing compounds (Dryseal Threads) arecovered in ASME B1.20.3.
1.5 Appendices
Useful and supplementary information that is not apart of this Standard is presented in a nonmandatoryappendix. Specifically, the nonmandatory appendicescover the turns of engagement method of gaging, sug-gested prethreading hole diameters, and an explanatorygaging matrix.
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ASME B1.20.1-2013
Fig. 1 Root, Crest, and Flank Engagement, NPT
External Thread
Internal Thread
Roots and crests clear
Roots and crests contact
Roots and crests interfere
1.6 Referenced Standards
The latest issues of the following documents form apart of this Standard to the extent specified herein.
ASME B1.2, Gages and Gaging for Unified ScrewThreads
ASME B1.7, Screw Threads: Nomenclature, Definitions,and Letter Symbols
ASME B1.20.3, Dryseal Pipe Threads (Inch)ASME B1.20.7, Hose Coupling Screw Threads (Inch)ASME B1.30, Screw Threads: Standard Practice for
Calculating and Rounding DimensionsASME B47.1, Gage Blanks
Publisher: The American Society of MechanicalEngineers (ASME), Two Park Avenue, New York, NY10016-5990; Order Department: 22 Law Drive, P.O.Box 2900, Fairfield, NJ 07007-2900 (www.asme.org)
1.7 Terminology
Definitions of terms and symbols for thread dimen-sions are given in ASME B1.7.
2
2 AMERICAN NATIONAL STANDARD PIPE THREADFORM
2.1 Thread Form
The form of thread profile specified in this Standardshall be known as the American National Standard PipeThread Form (see Fig. 2).
2.2 Angle of Thread
The angle between the sides of the thread is 60 degwhen measured in an axial plane. The line bisecting thisangle is perpendicular to the axis.
2.3 Thread Height
The height of the sharp V thread, H, is
H p 0.86602540P
where
P p pitch of thread
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ASME B1.20.1-2013
Fig. 2 Basic Form of American National Standard Taper Pipe Thread, NPT
External Thread Internal Thread
Axis
90 deg 90 deg
60 deg
90 deg 90 deg
Crest
Root
Frs
frsh
H
Fcs
fcs
fcn
Fcn
Crest
RootP
frn
Frn
90 deg
3
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ASME B1.20.1-2013
For a symmetrical straight screw thread with a 30-degflank angle, H p cot �/2n p 0.86602540P. For a symmet-rical taper screw thread with a 30-deg flank angle anddiametral taper of 0.750 in./ft, H p (cot � − tan2 � tan�)/2n p 0.86574320P. For an 8-pitch thread, which isthe coarsest standard taper pipe thread pitch, the corres-ponding values of H are 0.1082179 and 0.1082532, respec-tively. The difference of 0.000035 in. being insignificant,the value of H p 0.86602540P is used for all straightand tapered threads in this Standard.
2.4 Thread Truncation
The maximum height of the truncated thread, h (seeFig. 2), is based on factors entering into the manufactureof cutting tools and the making of tight joints.
h p 0.800P
The crest and root of pipe threads are truncated aminimum of 0.033P. The maximum depth of truncationfor the crest and root of these pipe threads will be foundin Table 1. The crests and roots of the external and inter-nal threads may be truncated either parallel to the pitchline or parallel to the axis. The illustration in Table 1,giving a sectional view of this Standard thread form,represents the truncated thread form by a straight lineand sharp corners. However, a radius form is acceptable,as long as the crests and roots lie within the limits shownin Table 1. Some of the truncations in this illustrationare shown with dotted lines as radii.
3 SPECIFICATION FOR TAPER PIPE THREADS, NPT
3.1 General
NPT joints made in accordance with these specifica-tions consist of an external taper and internal taperthread (see Figs. 1 through 3). NPT taper pipe threadsare intended to be made up wrench-tight and with asealant when a pressure-tight joint is required.
3.1.1 Notation. The standard notation applicableto the American National Standard Taper Pipe Thread,NPT, is shown in Fig. 3.
3.1.2 Symbols. The following symbols are specificto this Standard:
D p outside diameter of pipeE0 p basic pitch diameter at small end of external
thread (or end of pipe)E1 p basic pitch diameter at plane of hand-tight
engagement length (L1), external thread, andlarge end of internal thread
E2 p basic pitch diameter at plane of effectivethread length (L2), external thread
E3 p basic pitch diameter at plane of wrench-tightengagement
E5 p basic pitch diameter pipe at L5, plane of com-plete thread length
4
K0 p basic minor diameter at small end of externalthread (or end of pipe)
L1 p length of hand-tight engagement betweeninternal and external threads
L2 p length of effective thread, external thread.Equal to L1 plus wrench make-up threads
L3 p length of thread beyond L1 allowing wrench-tight engagement, internal thread (also,wrench make-up)
L4 p overall length of thread, including vanishthread, external thread
L5 p length of complete threads, external thread,where cone of major diameter intersects out-side diameter of pipe
V p length of vanish threads
3.1.3 Handling Considerations. The potential effectson thread form and gaging must be considered whenchoosing coatings and other processes. Some processes,such as barrel coating, can be damaging to the threadform, especially the crests of external threads. See para.3.2.3 on gaging nicked threads.
3.1.4 Form of Thread. The form of the thread isspecified in para. 2.1.
3.1.5 Taper of Thread. The basic taper of the threadis 1 in 16 or 0.75 in./ft measured diametrically relativeto the axis.
3.1.6 Pitch Diameters of Thread. The basic pitchdiameters of the tapered thread are determined by thefollowing formulas based on the outside diameter of thepipe and the pitch of the thread:
E0 p D − (0.05D + 1.1) 1/np D − (0.05D + 1.1)P
E1 p E0 + 0.0625 L1
whereD p outside diameter of pipeE0 p pitch diameter of thread at end of pipe or
small end of external threadE1 p pitch diameter of thread at the large end of
internal threadL1 p hand-tight length of engagement between
external and internal threads, also the hand-tight length of thread for both internal andexternal threads
n p threads per inch
3.1.7 Length of Effective Thread. The basic lengthof the effective external taper thread L2, is determinedby the following formula based on the outside diameterof the pipe and the pitch of the thread:
L2 p (0.80D + 6.8)1/np (0.80D + 6.8)P
whereD p outside diameter of pipen p threads per inch
Copyright ASME International Provided by IHS under license with ASME Licensee=CTCI Corporation/5926309001, User=Wang, Hsien Yu
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ASME B1.20.1-2013
Table 1 Limits on Crest and Root Truncation of American National Standard External andInternal Taper Pipe Threads, NPT
Minimum truncation
Maximum truncation
Minimum truncation
Maximum truncation
External Thread
Internal Thread
Root
Crest
Crest
Root
Crest
Minimum truncation
Maximum truncation
Minimum truncation
Maximum truncation
Max. h
H
Truncation, f Equivalent Width of Flat, FHeight of Thread,Height ofh Min. Max. Min. Max.Threads/ Sharp V
Inch, n Thread, H Min. Max. Formula in. Formula in. Tolerance Formula in. Formula in. Tolerance
1 2 3 4 5 6 7 8 9 10 11 12 13 14
27 0.0320750 0.02496 0.02963 0.033P 0.0012 0.096P 0.0036 0.0024 0.038P 0.0014 0.111P 0.0041 0.002718 0.0481125 0.03833 0.04444 0.033P 0.0018 0.088P 0.0049 0.0031 0.038P 0.0021 0.102P 0.0057 0.003614 0.0618590 0.05072 0.05714 0.033P 0.0024 0.078P 0.0056 0.0032 0.038P 0.0027 0.090P 0.0064 0.003711.5 0.0753066 0.06261 0.06957 0.033P 0.0029 0.073P 0.0063 0.0034 0.038P 0.0033 0.084P 0.0073 0.0040
8 0.1082532 0.09275 0.100 0.033P 0.0041 0.062P 0.0078 0.0037 0.038P 0.0048 0.072P 0.0090 0.0042
GENERAL NOTE: The basic dimensions of the American National Standard Taper Pipe Thread are given in inches to four or five decimal places.While this implies a greater degree of precision than is ordinarily attained, these dimensions are the basis of gage dimensions and are soexpressed for the purpose of eliminating errors in computations.
5
Copyright ASME International Provided by IHS under license with ASME Licensee=CTCI Corporation/5926309001, User=Wang, Hsien Yu
Not for Resale, 12/26/2013 16:53:44 MSTNo reproduction or networking permitted without license from IHS
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ASME B1.20.1-2013
Fig. 3 American National Standard Taper Pipe Thread Notation
Pla
ne
of
wre
nch
mak
e-u
p
Ref
eren
ce p
lan
e
zero
Pla
ne
of
han
d-t
igh
t
eng
agem
ent
Pla
ne
of
com
ple
te
thre
ad le
ng
th
Pla
ne
of
effe
ctiv
e
Pla
ne
of
van
ish
po
int
thre
ad le
ng
th
Wrench make-up
L3 L1
L5
L2
L4
V
2P
E2 d DE5E1E0K0E3
6
Copyright ASME International Provided by IHS under license with ASME Licensee=CTCI Corporation/5926309001, User=Wang, Hsien Yu
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ASME B1.20.1-2013
This formula determines the length of effective exter-nal thread. This may include two usable threads incom-plete at the crest.
3.1.8 Hand-Tight Engagement Between External andInternal Taper Threads. The basic length of engagementbetween external and internal taper threads whenscrewed together hand-tight is L1, shown in column 6,Table 2.
3.1.9 Wrench-Tight Engagement Between Externaland Internal Taper Threads. The external thread length,L2 − L1, and the internal thread length, L3, are allowancesfor wrench-tight assembly after the hand-tight engage-ment of L1 lengths.
3.1.9.1 Thread Engagement Considerations. Thegaging tolerance of ±1 turn for both external and internalthreads has the effect of potentially increasing the lengthof engagement by up to two turns or reducing the lengthof engagement by up to two turns. Working gage wearhas the additional effect of reducing thread engagementby the amount gages wear past basic.
3.1.9.2 Special Applications. It is recognized thatin special applications, such as flanges for high-pressurework, longer thread engagement is needed, in whichcase the pitch diameter (dimension E1, Table 2) is main-tained and the pitch diameter E0 at the end of the pipeis made smaller. The taper must be kept at 3⁄4 in./ft, andthread is made longer.
3.1.10 Tolerances on Product Taper, Lead, andAngle. The permissible variations in taper, lead, andangle are given in Table 3. This table is a guide forestablishing limits of the thread elements of threadingtools. The correct manufacture of tools and the use ofgages should provide adequate control of functionalsize.
3.1.11 Basic Dimensions. The basic dimensions oftaper pipe threads, derived from the above specifica-tions, are given in Table 2.
3.2 Gaging NPT ThreadsThe L1 gages prescribed in this Standard are consid-
ered functional in that they give assurance of assembla-bility over the L1 length, the length of hand-tightengagement. They simulate a mating product thread thatconforms to this Standard. They encompass multipleelements of the thread, including thread diameters, flankangle, lead, taper, and root truncation. The simultaneousengagement of all elements results in a measurementthat reflects the cumulative variation of all those ele-ments, the functional diameter. This is expressed asstandoff for rings and plugs or measured directly byindicating gages. See section 7 for gage specifications.
3.2.1 External Thread Gaging
3.2.1.1 L1 Ring Gage. The L1 ring and externalproduct thread are screwed together hand-tight, and the
7
position relative to the small end of the ring (or basicstep on a stepped ring gage) is noted (see Figs. 4 and5). This is the standoff. The tolerance for the standoff is±1 turn (or ±1 pitch, as shown in column 4 of Table 2)from the small end of the ring (or basic step on astepped ring).
3.2.1.2 External L1-Indicating Gage. The externalL1-indicating gage is set with a master plug gage, whichis made to basic dimensions. Accordingly, when theproduct is engaged by an indicating gage, readings indi-cate the diametral variation from basic. The tolerancefrom basic is the diametral equivalent to ±1 pitch (or±0.0625/n, as shown in column 23 of Table 2).
3.2.2 Internal Thread Gaging
3.2.2.1 L1 Plug Gage. The L1 plug gage and inter-nal product thread are screwed together hand-tight, andthe position relative to the basic step of the gage is noted(see Figs. 5 and 6). This is the standoff. The tolerancefor the standoff is ±1 turn (or ±1 pitch, as shown incolumn 4 of Table 2) from the basic step of the plug gage.
3.2.2.2 Internal L1-Indicating Gage. The internalL1-indicating gage is set with a master ring gage, whichis made to basic dimensions. Accordingly, when theproduct is engaged by an indicating gage, readings indi-cate the diametral variation from basic. The tolerancefrom basic is the diametral equivalent to ±1 pitch (or±0.0625/n, as shown in column 23 of Table 2).
3.2.3 Nicked Threads. Pipe threads are particularlysusceptible to damage that interferes with proper gag-ing. Generally, this damage appears as “nicks” on thecrest of external or internal threads. These nicks willalways hold the gage back from properly seating. Thismakes the external functional size seem larger than itis and the internal functional size seem smaller than itis. Because pipe threads are designed to be installedwrench-tight, and the wrenching reforms the nicks totheir proper crest position, some degree of nicking isacceptable. A product mated with a gage may be“rapped” and hand-tightened while engaged. Careshould be exercised when rapping to minimize thepotential damage to the gage. Rapping and tighteningmay continue until the product and gage do not engageany further. Products that remain beyond the gagingtolerance after rapping and hand-tightening arenonconforming.
3.2.4 Treatment of Chamfers, Recesses,Counterbores. Threaded products have thread cham-fers to avoid sharp edges, protect the start thread, andaid in assembly. The nature of threads generally necessi-tates external chamfer diameters at least as small as theminor diameter and internal chamfer diameters at leastas large as the major diameter, if complete sharp edgeremoval is desired. In practice, many product threadchamfers exceed the minimal chamfer that removes the
Copyright ASME International Provided by IHS under license with ASME Licensee=CTCI Corporation/5926309001, User=Wang, Hsien Yu
Not for Resale, 12/26/2013 16:53:44 MSTNo reproduction or networking permitted without license from IHS
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ASME B1.20.1-2013
Tabl
e2
Bas
icD
imen
sion
sof
Amer
ican
Nat
iona
lSt
anda
rdTa
per
Pipe
Thre
ad,
NPT
L 4
V
2P
E2
DE
5E
1E
0K
0E
3
L 2
L 5
L 3L 1
Van
ish
th
read
s d
ue
to c
ham
fer
on
die
Tap
er o
f th
read
1 in
16
mea
sure
d o
n d
iam
eter
8
Copyright ASME International Provided by IHS under license with ASME Licensee=CTCI Corporation/5926309001, User=Wang, Hsien Yu
Not for Resale, 12/26/2013 16:53:44 MSTNo reproduction or networking permitted without license from IHS
--``,,,,`,`,,`,`````,`,,`,`,`-`-`,,`,,`,`,,`---
ASME B1.20.1-2013
Tabl
e2
Bas
icD
imen
sion
sof
Amer
ican
Nat
iona
lSt
anda
rdTa
per
Pipe
Thre
ad,
NPT
(Con
t’d)
Basi
cPi
tch
Chan
geM
inor
6
Leng
th,L
1Di
amet
erin
Diam
eter
Hand
-tigh
tEf
fect
ive
Thre
ad,
Plan
eto
L 2No
min
alCo
mpl
ete
atDi
amet
erat
Wre
nch
Mak
e-Up
Leng
th,
Enga
gem
ent
Exte
rnal
Plan
e,Ex
tern
alTh
read
s5
Begi
nnin
gO
vera
llpe
rSm
all
Inte
rnal
Thre
adEx
tern
alVa
nish
O.D.
Pitc
hof
Pitc
hPi
tch
Leng
th,
Pitc
hHe
ight
Turn
End
Leng
th,1
Leng
th,3
Thre
ad,
Leng
th,
Thre
ad,
Leng
th,
Nom
inal
ofof
Exte
rnal
Diam
-Di
am-
Pitc
hEx
tern
alDi
am-
ofof
ofL 1
L 2L 2
−L 1
L 3V
L 5Pi
pePi
pe,
Thre
ads/
Thre
ad,
Thre
ad,
eter
,2et
er,
Diam
-Th
read
,4et
er,
Thre
ad,
Thre
ad,
Pipe
,Si
zeD
Inch
,nP
E 0in
.Th
read
sE 1
in.
Thre
ads
E 3in
.Th
read
sin
.Th
read
set
er,E
3in
.Th
read
sL 4
in.
E 5h
0.06
25/n
K o
12
34
56
78
910
1112
1314
1516
1718
1920
2122
2324
1 ⁄ 160.
3125
270.
0370
3704
0.27
118
0.16
004.
320.
2811
80.
2611
7.05
0.28
750
0.10
112.
730.
1111
30.
2642
40.
1285
3.47
0.38
960.
1870
0.28
287
0.02
963
0.00
231
0.24
151 ⁄ 8
0.40
5027
0.03
7037
040.
3635
10.
1615
4.36
0.37
360
0.26
397.
130.
3800
00.
1024
2.76
0.11
113
0.35
656
0.12
853.
470.
3924
0.18
980.
3753
70.
0296
30.
0023
10.
3338
1 ⁄ 40.
5400
180.
0555
5556
0.47
739
0.22
784.
100.
4916
30.
4018
7.23
0.50
250
0.17
403.
130.
1667
30.
4669
70.
1928
3.47
0.59
460.
2907
0.49
556
0.04
444
0.00
347
0.43
293 ⁄ 8
0.67
5018
0.05
5555
560.
6120
10.
2400
4.32
0.62
701
0.40
787.
340.
6375
00.
1678
3.02
0.16
673
0.60
160
0.19
283.
470.
6006
0.29
670.
6305
60.
0444
40.
0034
70.
5675
1 ⁄ 20.
8400
140.
0714
2857
0.75
843
0.32
004.
480.
7784
30.
5337
7.47
0.79
178
0.21
372.
990.
2143
30.
7450
40.
2479
3.47
0.78
150.
3909
0.78
286
0.05
714
0.00
446
0.70
14
3 ⁄ 41.
0500
140.
0714
2857
0.96
768
0.33
904.
750.
9888
70.
5457
7.64
1.00
178
0.20
672.
890.
2143
30.
9542
90.
2479
3.47
0.79
350.
4029
0.99
286
0.05
714
0.00
446
0.91
061
1.31
5011
.50.
0869
5652
1.21
363
0.40
004.
601.
2386
30.
6828
7.85
1.25
631
0.28
283.
250.
2609
31.
1973
30.
3017
3.47
0.98
450.
5089
1.24
544
0.06
957
0.00
543
1.14
4111 ⁄ 4
1.66
0011
.50.
0869
5652
1.55
713
0.42
004.
831.
5833
80.
7068
8.13
1.60
131
0.28
683.
300.
2609
31.
5408
30.
3017
3.47
1.00
850.
5329
1.59
044
0.06
957
0.00
543
1.48
7611 ⁄ 2
1.90
0011
.50.
0869
5652
1.79
609
0.42
004.
831.
8223
40.
7235
8.32
1.84
131
0.30
353.
490.
2609
31.
7797
80.
3017
3.47
1.02
520.
5496
1.83
044
0.06
957
0.00
543
1.72
662
2.37
5011
.50.
0869
5652
2.26
902
0.43
605.
012.
2962
70.
7565
8.70
2.31
630
0.32
053.
690.
2609
32.
2527
20.
3017
3.47
1.05
820.
5826
2.30
543
0.06
957
0.00
543
2.19
95
21 ⁄ 22.
8750
80.
1250
0000
2.71
953
0.68
205.
462.
7621
61.
1375
9.10
2.79
063
0.45
553.
640.
2500
22.
7039
10.
4338
3.47
1.57
120.
8875
2.77
500
0.10
000
0.00
781
2.61
953
3.50
008
0.12
5000
003.
3406
30.
7660
6.13
3.38
850
1.20
009.
603.
4156
30.
4340
3.47
0.25
002
3.32
500
0.43
383.
471.
6337
0.95
003.
4000
00.
1000
00.
0078
13.
2406
31 ⁄ 24.
0000
80.
1250
0000
3.83
750
0.82
106.
573.
8888
11.
2500
10.0
03.
9156
30.
4290
3.43
0.25
002
3.82
188
0.43
383.
471.
6837
1.00
003.
9000
00.
1000
00.
0078
13.
7374
44.
5000
80.
1250
0000
4.33
438
0.84
406.
754.
3871
31.
3000
10.4
04.
4156
30.
4560
3.65
0.25
002
4.31
875
0.43
383.
471.
7337
1.05
004.
4000
00.
1000
00.
0078
14.
2343
55.
5630
80.
1250
0000
5.39
073
0.93
707.
505.
4492
91.
4063
11.2
55.
4786
30.
4693
3.75
0.25
002
5.37
511
0.43
383.
471.
8400
1.15
635.
4630
00.
1000
00.
0078
15.
2907
66.
6250
80.
1250
0000
6.44
609
0.95
807.
666.
5059
71.
5125
12.1
06.
5406
30.
5545
4.44
0.25
002
6.43
047
0.43
383.
471.
9462
1.26
256.
5250
00.
1000
00.
0078
16.
3460
88.
6250
80.
1250
0000
8.43
359
1.06
308.
508.
5000
31.
7125
13.7
08.
5406
30.
6495
5.20
0.25
002
8.41
797
0.43
383.
472.
1462
1.46
258.
5250
00.
1000
00.
0078
18.
3335
1010
.750
08
0.12
5000
0010
.545
311.
2100
9.68
10.6
2094
1.92
5015
.40
10.6
6563
0.71
505.
720.
2500
210
.529
690.
4338
3.47
2.35
871.
6750
10.6
500
0.10
000
0.00
781
10.4
453
1212
.750
08
0.12
5000
0012
.532
811.
3600
10.8
812
.617
812.
1250
17.0
012
.665
630.
7650
6.12
0.25
002
12.5
1719
0.43
383.
472.
5587
1.87
5012
.650
00.
1000
00.
0078
112
.432
814
14.0
000
80.
1250
0000
13.7
7500
1.56
2012
.50
13.8
7263
2.25
0018
.00
13.9
1563
0.68
805.
500.
2500
213
.759
380.
4338
3.47
2.68
372.
0000
13.9
000
0.10
000
0.00
781
13.6
749
1616
.000
08
0.12
5000
0015
.762
501.
8120
14.5
015
.875
752.
4500
19.6
015
.915
630.
6380
5.10
0.25
002
15.7
4688
0.43
383.
472.
8837
2.20
0015
.900
00.
1000
00.
0078
115
.662
418
18.0
000
80.
1250
0000
17.7
5000
2.00
0016
.00
17.8
7500
2.65
0021
.20
17.9
1563
0.65
005.
200.
2500
217
.734
380.
4338
3.47
3.08
372.
4000
17.9
000
0.10
000
0.00
781
17.6
499
2020
.000
08
0.12
5000
0019
.737
502.
1250
17.0
019
.870
312.
8500
22.8
019
.915
630.
7250
5.80
0.25
002
19.7
2188
0.43
383.
473.
2837
2.60
0019
.900
00.
1000
00.
0078
119
.637
424
24.0
000
80.
1250
0000
23.7
1250
2.37
5019
.00
23.8
6094
3.25
0026
.00
23.9
1563
0.87
507.
000.
2500
223
.696
880.
4338
3.47
3.68
373.
0000
23.9
000
0.10
000
0.00
781
23.6
124
GEN
ERA
LN
OTE
:Th
eba
sic
dim
ensi
ons
ofth
eA
mer
ican
Nat
iona
lS
tand
ard
Tape
rPi
peTh
read
are
give
nin
inch
esto
four
orfiv
ede
cim
alpl
aces
.W
hile
this
impl
ies
agr
eate
rde
gree
ofpr
ecis
ion
than
isor
dina
rily
atta
ined
,th
ese
dim
ensi
ons
are
the
basi
sof
gage
dim
ensi
ons
and
are
soex
pres
sed
for
the
purp
ose
ofel
imin
atin
ger
rors
inco
mpu
tati
ons.
NO
TES
:(1
)A
lso
leng
thof
L 1ri
ngga
gean
dle
ngth
from
gagi
ngno
tch
tosm
all
end
ofL 1
plug
gage
.(2
)A
lso
pitc
hdi
amet
erat
gagi
ngno
tch
ofL 1
plug
gage
(han
d-ti
ght
plan
e).
(3)
Als
oth
read
edle
ngth
ofL 1
plug
gage
.(4
)Re
fere
nce
dim
ensi
on.
(5)
The
leng
thL 5
from
the
end
ofth
epi
pede
term
ines
the
plan
ebe
yond
whi
chth
eth
read
form
isin
com
plet
eat
the
cres
t.Th
ene
xttw
oth
read
sar
eco
mpl
ete
atth
ero
ot.
At
this
plan
e,th
eco
nefo
rmed
byth
ecr
ests
ofth
eth
read
inte
rsec
tsth
ecy
linde
rfo
rmin
gth
eex
tern
alsu
rfac
eof
the
pipe
(L5
pL 2
−2P
).(6
)G
iven
asin
form
atio
nfo
rus
ein
sele
ctin
gta
pdr
ills
(see
Non
man
dato
ryA
ppen
dix
B).
9
Copyright ASME International Provided by IHS under license with ASME Licensee=CTCI Corporation/5926309001, User=Wang, Hsien Yu
Not for Resale, 12/26/2013 16:53:44 MSTNo reproduction or networking permitted without license from IHS
--``,,,,`,`,,`,`````,`,,`,`,`-`-`,,`,,`,`,,`---
ASME B1.20.1-2013
Table 3 Tolerances on Taper, Lead, and Angle of Pipe Threads, NPT
Tolerances
Taper on Pitch Line,3⁄4 in./ftThreads/ Lead in Effective 60-deg Angle of
Nominal Pipe Size Inch, n Max. Min. Length of Threads Threads, Deg
1 2 3 4 5 6
1⁄16, 1⁄8 27 +1⁄8 −1⁄16 ±0.003 ±21⁄21⁄4, 3⁄8 18 +1⁄8 −1⁄16 ±0.003 ±21⁄2, 3⁄4 14 +1⁄8 −1⁄16 ±0.003 ±2
1, 11⁄4, 11⁄2, 2 11.5 +1⁄8 −1⁄16 ±0.003 ±11⁄221⁄2 and larger 8 +1⁄8 −1⁄16 ±0.003 [Note (1)] ±11⁄2
NOTE:(1) The tolerance on lead shall be ±0.003 in./in. on any size threaded to an effective thread length greater than 1 in.
Fig. 4 Gaging External Taper Threads With L1 Ring Gage
(a) Basic Size (b) Maximum Size (c) Minimum Size
Ring gage Ring gage Ring gage
Flush One turn large
One turn small
10
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Fig. 5 Gaging of Chamfered Threads
Chamfered Internal Thread
of Basic Size With Chamfer
Exceeding the Major Diameter
Chamfered External Thread
of Basic Size With Chamfer
Diameter Smaller Than
the Minor Diameter
Chamfered External Thread of
Basic Size With the Chamfer
Diameter the Same as
the Minor Diameter
Chamfered Internal Thread
of Basic Size With Chamfer
Diameter the Same as the
Major Diameter
Ring gage
Ring gage
Pipe or fitting
Pipe or fitting
Gaging face
Point of last thread scratch
Gaging face
Point of last thread scratch
Fitting
Plug gage
Fitting
Plug gage
Point of last thread scratch
Point of last thread scratch
Plane of gaging notch
Plane of gaging notch
(c)
(a) (b)
(d)
GENERAL NOTE: See para. 3.2.4.
11
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Fig. 6 Gaging Internal Taper Threads With L1 Plug Gage
(a) Basic Size (b) Maximum Size (c) Minimum Size
Plug gage
Plug gage
Plug gage
Flush One turn large One turn small
sharp edge to better ensure sharp edge removal. Theexistence of chamfers has the effect of reducing engagedthread length, and larger chamfers further reduce threadlength. Designers and manufacturers are therefore cau-tioned to take into consideration the effects of chamferson the intended assembly. The gaging reference pointfor a product thread depends on the chamfer diameter.
3.2.4.1 For an external thread with a chamferdiameter smaller than the minor diameter, the referencepoint is the last scratch of the chamfer cone [see Fig. 5,illustration (a)].
3.2.4.2 For an internal thread with a chamferdiameter larger than the major diameter, the referencepoint is the last scratch of the chamfer cone [see Fig. 5,illustration (b)].
3.2.4.3 For an external thread with a chamferdiameter equal to or greater than the minor diameter,the reference point is the end of the fitting [or pipe; seeFig. 5, illustration (c)].
3.2.4.4 For an internal thread with a chamferdiameter equal to or smaller than the major diameter,the reference point is the end of the fitting [see Fig. 5,illustration (d)].
3.2.4.5 Recesses and counterbores must beaccounted for when gaging internal threads. Dogpointsor lead-ins to external threads must be accounted for
12
when gaging external threads. These features must notbe included in thread length measurements.
3.2.5 Acceptance of Product Made Prior to This Revi-sion. This revision includes changes to gaging practice,specifically the changing of the gaging point of referencefor external threads having chamfer diameters smallerthan the minor diameter at the small end. This changeis an important advance and should be implementedupon issuance of this Standard. As long as there are nospecifically identified assembly issues, products con-forming to the prior revision of this document are con-sidered suitable and allowed for sale and acceptanceuntil depleted.
3.2.6 Coated Threads. The specifications in thisStandard do not include an allowance for coating (orplating). If coating is desired, it may be necessary tomodify the threads since the gaging requirements mustbe satisfied for coated and uncoated parts. This may beemphasized by adding the words “AFTER COATING”to the thread designation of the finished product. Gagelimits before coating may be specified, followed by thewords “BEFORE COATING” or “PRE-PLATE.”
3.2.6.1 Coating Buildup. If significant, a coatingbuildup will necessitate making external threads smallerand internal threads larger, so that after coating, threadsizes and gaging are conforming to the Standard. It isimportant to note that coating buildup on the flanks of
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threads increases external thread pitch diameter sizesand reduces internal pitch diameter sizes by four timesthe coating thickness. Coating buildup in crests androots increases major diameter sizes and decreasesminor diameter sizes by two times the coating thickness.See paras. 3.2.6.2 and 3.2.6.3 for guidance on compensat-ing for uniform coatings. Many product coatings do notcoat features evenly. Information about coating buildupshould be obtained from the coating processor.
3.2.6.2 Precoating Gaging Standoff Compensation,Internal Thread. Thread gaging standoff tolerance maybe adjusted to compensate for a uniform coating withan upper and lower thickness tolerance in the followingmanner:EXAMPLE: 1⁄2–14 NPT internal thread with uniform coatingthickness of 0.0002 in. to 0.0004 in. After coating, final producttolerance is flush ±1 turn standoff. Before coating, tolerance isestablished by the following formula:
Large end of product tolerance:1 turn large + (minimum coating thickness � 60-deg thread
constant � taper standoff constant)or0.0714 in. large + (0.0002 in. � 4 � 16) p 0.0842 in. large
Small end of product tolerance:1 turn small − (maximum coating thickness � 60-deg thread
constant � taper standoff constant)or0.0714 in. small − (0.0004 in. � 4 � 16) p 0.0458 in. small
Calculated before coating standoff tolerance: 0.0842 in. large to0.0458 in. small.
Threads with nonuniform coatings or other residualeffects (like nicks) may have to be compensated for dif-ferently to obtain standard after-coating tolerances.
3.2.6.3 Precoating Gaging Standoff Compensation,External Thread. Thread gaging standoff tolerance maybe adjusted to compensate for a uniform coating withan upper and lower thickness tolerance in the followingmanner:EXAMPLE: 1⁄2–14 NPT external thread with uniform coatingthickness of 0.0002 in. to 0.0004 in. After coating, final producttolerance is flush ±1 turn standoff. Before coating, tolerance isestablished by the following formula:
Small end of tolerance:1 turn small + (minimum coating thickness � 60-deg thread
constant � taper standoff constant)or0.0714 in. small + (0.0002 in. � 4 � 16) p 0.0842 in. small
Large end of tolerance:1 turn large − (maximum coating thickness � 60-deg thread
constant � taper standoff constant)or0.0714 in. large − (0.0004 in. � 4 � 16) p 0.0458 in. large
Calculated before coating standoff tolerance: 0.0842 in. small to0.0458 in. large.
13
Threads with nonuniform coatings or other residualeffects (like nicks) may have to be compensated for dif-ferently to obtain standard after-coating tolerances.
3.2.6.4 Precoating Gages. Special modified ringand plug gages may be designed and used in place ofthe standoff compensation methods described above.These are based on the standard gages described insection 7. It is common to modify the gage diameterssuch that the plug’s basic step and the small end ofthe ring are flush with product threads that are at acompensated basic size. Formulas similar to those abovemay be used in arriving at modified gage sizes.
3.2.7 Supplemental Gaging Conformance to thisStandard requires that all basic design dimensions bemet (within applicable tolerances), including taper,thread truncations, lead, and thread flank angle over theL2 and L3 lengths. Since the gaging systems prescribedin this Standard may not ensure conformance to theseindividual thread elements, supplemental gaging maybe employed to evaluate conformance. When supple-mental gaging is employed, it shall be agreed upon bythe supplier and purchaser. It is common to measuretruncation equivalent width of flat (Table 1) by opticalprojection of external threads directly to determinewhether or not such truncations are within the limitsspecified or particularly to see that maximum truncationis not exceeded.
3.3 Acceptability
Thread gages made to this Standard will have varia-tion between them due to gage manufacturing tolerancesand allowable gage wear. There can be more variationin tapered thread gaging than straight thread gaging dueto the interplay of the taper variations (within tolerance)between gages and products. The functional gagingrequirement of this Standard will be met when the prod-uct is accepted by a gage that conforms to this Standard.It is acknowledged that the allowable differences in con-forming gages may produce wider ranges of productdimensions than would be constructed strictly by thethread drawings and tolerances. However, product func-tionality and interchangeability are ultimately met usingthese gages.
4 SPECIFICATIONS FOR INTERNAL STRAIGHTTHREADS IN PIPE COUPLINGS, NPSC
4.1 Pressure-Tight Internal Straight Pipe Threads
Threads made in accordance with these specificationsare straight (parallel) threads of the same thread formas the American National Standard Taper Pipe Threadspecified in para. 2.1. They are used to form pressure-tight joints when assembled with an NPT external taperthread and made up wrench-tight with sealant (seepara. 1.4).
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Table 4 Dimensions, Internal Straight Threads in Pipe Coupling, NPSC(Pressure-Tight Joints With Sealant)
Pitch Diameter [Note (1)]O.D. Pipe, Minimum MinorNominal Pipe Size D Threads/Inch, n Diameter Min. Max.
1 2 3 4 5 6
1⁄8 0.405 27 0.340 0.3701 0.37711⁄4 0.540 18 0.442 0.4864 0.49683⁄8 0.675 18 0.577 0.6218 0.63221⁄2 0.840 14 0.715 0.7717 0.78513⁄4 1.050 14 0.925 0.9822 0.99561 1.315 111⁄2 1.161 1.2305 1.2468
11⁄4 1.660 111⁄2 1.506 1.5752 1.591511⁄2 1.900 111⁄2 1.745 1.8142 1.8305
2 2.375 111⁄2 2.219 2.2881 2.304421⁄2 2.875 8 2.650 2.7504 2.7739
3 3.500 8 3.277 3.3768 3.400231⁄2 4.000 8 3.777 3.8771 3.9005
4 4.500 8 4.275 4.3754 4.3988
NOTE:(1) The actual pitch diameter of the straight tapped hole will be slightly smaller than the value given when gaged with a taper plug gage
as specified in para. 4.2.1.
4.1.1 Thread Designation. The American NationalStandard Coupling Straight Pipe Threads are designatedin accordance with para. 1.3.1 as follows:
1⁄8–27 NPSC
4.1.2 Dimensions and Limits of Size. The dimen-sions and pitch diameter limits of size are specified inTable 4. The pitch diameter sizes correspond to the gag-ing tolerance of one and one-half turns large or smallof the NPT E1. The major and minor diameters varywith the pitch diameter, as the American National Stan-dard Pipe Thread form is maintained within the trunca-tion tolerances shown in Table 1.
4.2 Gaging NPSC Internal Threads
Internal taper thread gages in accordance with section7 shall be used to gage NPSC straight internal pipethreads.
4.2.1 L1 Plug Gage. The L1 plug gage and internalproduct thread are screwed together hand-tight and theposition relative to the basic step of the gage is noted.This is the standoff. The NPSC tolerance for the standoffis ±11⁄2 turns (or ±11⁄2 pitch, as shown in column 4 ofTable 2) from the basic step of the plug gage. See paras.3.2.4.1 and 3.2.4.2 for chamfered threads.
4.2.2 L1 Internal Indicating Gage. When product isengaged in an indicating gage set with a master gage,readings indicate the diametral variation from basic. Thetolerance from basic is the diametral equivalent to ±11⁄2pitches (or ±0.0625/n, as shown in column 23 of Table 2).See paras. 3.2.4.1 and 3.2.4.2 for chamfered threads.
14
CAUTION: When using tapered thread gages in straight prod-uct threads, nonuniformity of gage wear is a particular problem;therefore, tapered gages used for this application should bechecked by direct measurement of thread form and size in addi-tion to checking against a master.
5 SPECIFICATIONS FOR RAILING JOINT TAPERPIPE THREADS, NPTR
5.1 Railing Joints
Railing joints that require a rigid mechanical taperthread joint may be made with external and internaltaper threads. The external thread is the same as theNPT thread, except that it is shortened to permit theuse of the larger end of the pipe thread. The internalthread has the same basic dimensions as the NPT inter-nal thread; however, a recess in the fitting provides acovering for the last scratch or sharp edges of incompletethreads on the pipe. The dimensions of these threadsare shown in Table 5.
5.1.1 Thread Designation. American National Stan-dard Railing Joint Taper Pipe Threads are designated inaccordance with para. 1.3.1 as follows:
1⁄2–14 NPTR
5.1.2 Form of Thread. The form of the thread is thesame as the American National Standard Taper PipeThread shown in Figs. 1 and 2.
5.2 Gaging and Tolerances, NPTR
The dimensions of these threads are specified in Table5. Gaging is performed using standard NPT L1 gages
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Tabl
e5
Dim
ensi
ons
ofEx
tern
alan
dIn
tern
alTa
per
Pipe
Thre
ads
for
Raili
ngJo
ints
,N
PTR
(Mec
hani
cal
Join
ts)
Do
tted
lin
es s
ho
w a
mo
un
t N
PT
sta
nd
ard
tap
er p
ipe
thre
ad is
s
ho
rten
ed a
t th
e en
d.
E6
L 6
D
Tap
er o
f t
hre
ad 1
in 1
6 m
easu
red
on
dia
met
er
V
L 6
L 2
L 4
L 2
NP
T L
1 th
read
gag
e
No
tch
S
Q
Tq
P
Max
imum
Max
imum
Inco
mpl
ete
Dis
tanc
eG
age1
Pitc
hM
inim
umM
inim
umLe
ngth
ofTo
tal
Leng
thof
Thre
ads
due
toN
otch
Com
esD
iam
eter
Dep
thof
Dia
.of
Sho
rten
ing
ofEf
fect
ive
Exte
rnal
Cham
fer
ofB
elow
Face
Hei
ght
atEn
dof
Rece
ssRe
cess
Thre
ad,
Thre
ad,
Thre
ad,
Dia
.,of
Fitt
ing,
O.D
.of
Thre
ads/
ofEx
tern
alin
inM
inim
umL 6
L 2−
L 6L 4
−L 6
VS
Nom
inal
Pipe
,In
ch,
Thre
ad,
Thre
ad,
Fitt
ing,
Fitt
ing,
Leng
th,
Pipe
Siz
eD
nh
E 6in
.Th
read
sin
.Th
read
sin
.Th
read
sin
.Th
read
sq
QT
in.
Thre
ads
12
34
56
78
910
1112
1314
1516
1718
1 ⁄ 20.
840
140.
0571
0.77
180.
214
30.
320
4.47
0.49
96.
980.
179
21 ⁄ 20.
180.
860.
250.
286
43 ⁄ 4
1.05
014
0.05
710.
9811
0.21
43
0.33
24.
640.
510
7.15
0.17
921 ⁄ 2
0.18
1.07
0.25
0.28
64
11.
315
11.5
0.06
961.
2299
0.26
13
0.42
24.
850.
639
7.35
0.21
721 ⁄ 2
0.22
1.34
0.30
0.34
84
11 ⁄ 41.
660
11.5
0.06
961.
5734
0.26
13
0.44
65.
130.
707
8.13
0.26
13
0.26
1.68
0.39
0.34
84
11 ⁄ 21.
900
11.5
0.06
961.
8124
0.26
13
0.46
35.
320.
724
8.33
0.26
13
0.26
1.92
0.43
0.34
84
22.
375
11.5
0.06
962.
2853
0.26
13
0.49
65.
700.
757
8.70
0.26
13
0.26
2.40
0.43
0.34
84
21 ⁄ 22.
875
80.
1000
2.75
080.
500
40.
638
5.10
1.01
38.
100.
375
30.
382.
900.
630.
625
53
3.50
08
0.10
003.
3719
0.50
04
0.70
05.
601.
075
8.60
0.37
53
0.38
3.53
0.63
0.62
55
31 ⁄ 24.
000
80.
1000
3.86
880.
500
40.
750
6.00
1.12
59.
000.
375
30.
384.
040.
630.
625
54
4.50
08
0.10
004.
3656
0.50
04
0.80
06.
401.
175
9.40
0.37
53
0.38
4.54
0.63
0.62
55
GEN
ERA
LN
OTE
:Th
ese
dim
ensi
ons
agre
ew
ith
thos
ede
velo
ped
byth
eM
anuf
actu
rers
Sta
ndar
diza
tion
Soc
iety
ofth
eVa
lve
and
Fitt
ings
Indu
stry
.Th
read
leng
ths
are
spec
ified
toth
ree
deci
mal
plac
esfo
rco
nven
ienc
e.
NO
TE:
(1)
Am
eric
anN
atio
nal
Sta
ndar
dTa
per
Pipe
Thre
adPl
ugG
age
(see
sect
ion
7).
15
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(see section 7). Since the basic length and size (Table 5,column 5) of the external thread have been reducedsignificantly from standard NPT, the start end of theproduct thread will always lie inside the face of the gage.The maximum allowable variation in the external threadis no turns large and one turn small from this modi-fied basic.
EXAMPLE:For a 1⁄2–14 NPTR external thread, Table 5, column 7: the startend of the modified basic thread lies three threads inside theface of the gage. The tolerance during gaging will be 2 turnslarge to 3 turns large.For a 1⁄2–14 NPTR internal thread, Table 5, column 18: the startend of the modified basic thread lies four threads inside theface of the fitting. The tolerance during gaging will be 4 turnslarge to 5 turns large.
6 SPECIFICATIONS FOR STRAIGHT PIPE THREADSFOR MECHANICAL JOINTS; NPSM, NPSL
6.1 Straight Pipe Threads for Mechanical Joints
In addition to pressure-tight pipe joints, for whichtaper external threads and taper or straight internalthreads can be used, there are mechanical joints wherestraight pipe threads are used. Their pitch diametersand root and crest truncations vary as described below.These types of joints are as follows:
(a) free-fitting mechanical joints for fixtures, Table 6,both external and internal, NPSM
(b) loose-fitting mechanical joints with lock-nuts,Table 7, both external and internal, NPSL
6.1.1 Thread Designations. These threads are desig-nated in accordance with para. 1.3.1 as follows:
1⁄8–27 NPSM
1⁄8–27 NPSL
6.1.2 Pitch and Flank Angle. The pitch and flankangle are the same as the corresponding dimensions ofthe taper pipe thread described in section 3.
6.1.3 Diameter of Thread. The basic pitch diameterfor both the external and internal threads is equal to E1of Table 2, which is the same as the large end of theinternal NPT thread.
6.2 Free-Fitting Mechanical Joints for Fixtures, NPSM
Pipe is often used for special applications where thereare no internal pressures and, consequently, no sealingrequirements. Also, straight pipe threads are sometimesfound more suited or convenient where straight threadjoints are required for mechanical assemblies. In thesecases, NPSM threads can be used, creating a reasonablyclose fit of mating parts. The dimensions of these threadsare given in Table 6. Gaging is described in para. 6.4.
16
6.3 Loose-Fitting Mechanical Joints With Locknuts,NPSL
The American National Standard External LocknutThread is designed to produce a pipe thread having thelargest diameter that is possible to cut on standard pipe.Ordinarily, straight internal threads are used with thesestraight external threads, providing a loose fit. Thedimensions of these threads are given in Table 7. It will benoted that the maximum major diameter of the externalthread is slightly greater than the nominal outside diam-eter of the pipe. The normal manufacturer’s variationin pipe diameter provides for this increase. One applica-tion of a taper pipe thread in combination with a locknutthread that has been in use for some time is that shownin Table 7. It consists of the nipple threaded joint usedto connect standpipes with the floor or wall of a watersupply tank.
6.4 Gaging for NPSM and NPSL Threads
Gaging to properly control the production of thesestraight threads should be through the use of GO andNOT GO gages or indicating type gages.
6.4.1 GO Gaging. The GO size is acceptable whenthe GO thread gage (plug or ring) freely engages thefull threaded length of the product.
6.4.2 NOT GO Gaging. The NOT GO size is accept-able when the NOT GO thread gage (plug or ring)applied to the product thread does not enter more thanthree complete turns. The gage should not be forced.Special conditions, such as exceptionally thin or ductilematerial, small number of threads, etc., may necessitatemodification of this practice.
6.4.3 Indicating Gages. When using indicatinggages for straight threads, refer to ASME B1.2 for use.
6.4.4 Gage Dimensions. Gages used for NPSM shallbe made to the pitch diameter limits specified in Table 6.Gages used for NPSL shall be made to the pitch diameterlimits specified in Table 7. These gages shall be madein accordance with standard practice for straight threadgages as outlined in ASME B1.2. The minimum majordiameter of the GO thread plug gage or internal func-tional indicating gage shall be equal to the minimumpitch diameter of the internal thread plus an amountequal to 0.64951905P. The maximum major diameter ofthe NOT GO thread plug gage shall be equal to themaximum pitch diameter of the internal thread plusan amount equal to 0.43301270P. The maximum minordiameter of the GO thread ring gage or external func-tional diameter indicating gage shall be equal to themaximum pitch diameter of the external thread minusan amount equal to 0.43301300P. The minimum minordiameter of the NOT GO thread ring gage shall be equalto the minimum pitch diameter of the external threadminus an amount equal to 0.21650635P.
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Table 6 Dimensions of External and Internal Straight Pipe Threads for Fixtures, NPSM(Free-Fitting Mechanical Joints)
External Thread Internal ThreadAxis
90 deg
Crest
Root
Fcs = 0.12500P
fcs = 0.10825P
hs = 0.64952P
hn = 0.54126PH = 0.866025P
60 deg
30 deg
30 deg
Crest
Root
Frs = 0.12500P
Frn = 0.12500P
frn = 0.10825P
fcn = 0.21651P
frs = 0.10825PFcn = 0.2500P
P
External Thread, Class 2A Internal Thread, Class 2BO.D. of
Major Diameter Pitch Diameter Minor Diameter Pitch DiameterNominal Pipe, Threads/Pipe Size D Inch Allowance Max. Min. Max. Min. Min. Max. Min.I Max.
1 2 3 4 5 6 7 8 9 10 11 12
1⁄8 0.405 27 0.0011 0.397 0.390 0.3725 0.3689 0.358 0.364 0.3736 0.37831⁄4 0.540 18 0.0013 0.526 0.517 0.4903 0.4859 0.468 0.481 0.4916 0.49743⁄8 0.675 18 0.0014 0.662 0.653 0.6256 0.6211 0.603 0.612 0.6270 0.63291⁄2 0.840 14 0.0015 0.823 0.813 0.7769 0.7718 0.747 0.759 0.7784 0.78513⁄4 1.050 14 0.0016 1.034 1.024 0.9873 0.9820 0.958 0.970 0.9889 0.9958
1 1.315 11.5 0.0017 1.293 1.281 1.2369 1.2311 1.201 1.211 1.2386 1.246211⁄4 1.660 11.5 0.0018 1.638 1.626 1.5816 1.5756 1.546 1.555 1.5834 1.591211⁄2 1.900 11.5 0.0018 1.877 1.865 1.8205 1.8144 1.785 1.794 1.8223 1.83022 2.375 11.5 0.0019 2.351 2.339 2.2944 2.2882 2.259 2.268 2.2963 2.304421⁄2 2.875 8 0.0022 2.841 2.826 2.7600 2.7526 2.708 2.727 2.7622 2.7720
3 3.500 8 0.0023 3.467 3.452 3.3862 3.3786 3.334 3.353 3.3885 3.398431⁄2 4.000 8 0.0023 3.968 3.953 3.8865 3.8788 3.835 3.848 3.8888 3.89884 4.500 8 0.0023 4.466 4.451 4.3848 4.3771 4.333 4.346 4.3871 4.39715 5.563 8 0.0024 5.528 5.513 5.4469 5.4390 5.395 5.408 5.4493 5.45986 6.625 8 0.0024 6.585 6.570 6.5036 6.4955 6.452 6.464 6.5060 6.5165
GENERAL NOTES:(a) NPSM threads have a form similar to that of UN threads and tolerances similar to 2A/2B. The internal thread has a minimum pitch
diameter equal to E1 of NPT threads.(b) The minor diameters of external threads and major diameters of internal threads are those as produced by commercial straight pipe
dies and commercial ground straight pipe taps. The major diameter of the external thread has been calculated on the basis of a trunca-tion of 0.10825P, and the minor diameter of the internal thread has been calculated on the basis of a truncation of 0.21651P, to pro-vide no interference at crest and root when product is gaged.
NOTE:(1) Column 11 is the same as the pitch diameter at the large end of internal thread, E1, Basic (see Table 2, column 8).
17
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ASME B1.20.1-2013
Table 7 Dimensions, External and Internal Straight Pipe Thread for Locknut Connections, NPSL(Loose-Fitting Mechanical Joints)
Locknut
Locknut
Tank floor or wall
Standard fitting with taper thread
Taper pipe thread
Straight locknut thread
External Threads Internal Threads
Nominal O.D. of MaximumI Minimum1
Pitch Diameter Pitch DiameterPipe Pipe, Threads/ Major MinorSize D Inch Diameter Max. Min. Diameter Min. Max.
1 2 3 4 5 6 7 8 9
1⁄8 0.405 27 0.409 0.3840 0.3805 0.362 0.3863 0.38981⁄4 0.540 18 0.541 0.5038 0.4986 0.470 0.5073 0.51253⁄8 0.675 18 0.678 0.6409 0.6357 0.607 0.6444 0.64961⁄2 0.840 14 0.844 0.7963 0.7896 0.753 0.8008 0.80753⁄4 1.050 14 1.054 1.0067 1.0000 0.964 1.0112 1.0179
1 1.315 11.5 1.318 1.2604 1.2523 1.208 1.2658 1.273911⁄4 1.660 11.5 1.663 1.6051 1.5970 1.553 1.6106 1.618711⁄2 1.900 11.5 1.902 1.8441 1.8360 1.792 1.8495 1.8576
2 2.375 11.5 2.376 2.3180 2.3099 2.265 2.3234 2.331521⁄2 2.875 8 2.877 2.7934 2.7817 2.718 2.8012 2.8129
3 3.500 8 3.503 3.4198 3.4081 3.344 3.4276 3.439331⁄2 4.000 8 4.003 3.9201 3.9084 3.845 3.9279 3.9396
4 4.500 8 4.502 4.4184 4.4067 4.343 4.4262 4.43795 5.563 8 5.564 5.4805 5.4688 5.405 5.4884 5.50016 6.625 8 6.620 6.5372 6.5255 6.462 6.5450 6.5567
8 8.625 8 8.615 8.5313 8.5196 8.456 8.5391 8.550810 10.750 8 10.735 10.6522 10.6405 10.577 10.6600 10.671712 12.750 8 12.732 12.6491 12.6374 12.574 12.6569 12.6686
NOTE:(1) As the American National Standard Straight Pipe Thread form of thread is produced by a single tool, the major and minor diameters of
the internal thread and the minor diameter of the external thread are presumed to vary with the pitch diameter. The major diameter ofthe external thread is usually determined by the diameter of the pipe. These theoretical diameters result from adding the depth of thetruncated thread (0.666025P) to the maximum pitch diameters in column 5, and it should be understood that commercial pipe will notalways have these maximum major diameters. The locknut thread is established on the basis of retaining the greatest possible amountof metal thickness between the bottom of the thread and the inside of the pipe. In order that a locknut may fit loosely on the exter-nally threaded part, an allowance equal to the increase in pitch diameter per turn is provided, with a tolerance of 1.5 turns for bothexternal and internal threads.
18
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ASME B1.20.1-2013
7 GAGES AND GAGE TOLERANCES FOR AMERICANNATIONAL STANDARD TAPER PIPE THREADS,NPT
7.1 Gage Design
Gages should be made of hardened steel and conformto the designs recommended in ASME B47.1 (see Figs. 7and 8).
7.1.1 Gages for External Threads. The L1 ring gageand indicating gage elements have a length equal todimension L1.
7.1.2 Gages for Internal Threads. The L1 plug andindicating gage elements have a length equal to dimen-sion L2. The L1 plug gage has a gaging notch located adistance L1 from the small end. In locating the basicgaging notch, the plane of the notch should intersectthe crest of the gage thread. The notched area of thelarge end of the plug gage shall remain sharp; however,it should not have burrs extending outside the threadform.
7.1.3 Partial End Threads. Partial end threads shallbe removed on both ends of the ring gage and both endsof the plug gage. This shall be done by chamfering tothe minor diameter of plugs and major diameter of ringsor “convolution” to full-form profile. This avoids possi-ble seating error from bent or malformed feathered edgeand protects the thread from chipping.
7.1.4 Marking of Gages. Each gage shall be markedso as to indicate clearly the nominal size of pipe, threadsper inch, and the proper thread series designation asgiven in the respective section of this Standard. Forrings, the marking shall be on the face of the large end.
7.2 Master Gages
Master gages are used to inspect working gages atthe times of manufacture and calibration. They are alsoused in setting indicating gages. Additionally, masterrings inspect master plugs, and master plugs inspectmaster rings. The L1 plug and ring master gages aremade to the basic dimensions specified in Table 8. Thethread roots of these gages shall clear a 0.0381P flator may be undercut beyond a sharp V. The crests aretruncated by 0.100P.
7.2.1 Master Gage Tolerances. Master gages shouldbe made to the basic dimensions as accurately as possi-ble, but in no case shall the cumulative variation exceedone-half of the total cumulative tolerance specified incolumns 13 and 14 of Table 9. A master ring and masterplug are mated, the large end of the ring seating flushat the plug notch within ±0.002 in. for sizes 1⁄16 through2, within ±0.003 in. for sizes 21⁄2 through 12, and within±0.005 in. for sizes 14 and larger. A supplementary checkby optical or other means should be made of flank angle
19
and form. Each master gage should be accompanied bya record of the measurements of all elements of thethread and the standoff of master plug or master ring(large end of ring gage to basic notch of plug gage).
CAUTION: It should be understood that only a specificallymatched set of masters (L1 plug and L1 ring) can be expected tomate with each other within the tolerance specified above andin General Note (a) of Table 9. There are many characteristics orvariations in gage elements that may combine to cause a signifi-cant standoff difference between master gages that are not specif-ically matched.
7.3 Working Gages
Working gages are used to inspect product threads.They are made to the basic dimensions given in Table 8.The roots of all gage threads shall clear 0.0381P width.A sharp V or undercut clearance is acceptable. The crestsare to be truncated an amount equal to 0.140P for 27threads per inch (tpi), 0.109P for 18 tpi, and 0.100P for14-tpi, 111⁄2-tpi, and 8-tpi threads (see Fig. 8). It is to benoted that these gages are truncated at the crest so thatthey bear only on the flanks of the thread. Thus, theydo not check the product crest or root truncations. Whenit is deemed necessary to determine whether or not suchtruncations are within the limits specified, or particu-larly that the maximum truncations are not exceeded,optical projection is one common method.
7.3.1 Working Gage Tolerances. Working gagesshould be made to the basic dimensions specified inTable 8 and within tolerances specified in Table 9. Themaximum wear on a working plug gage shall not bemore than the equivalent of 1⁄4 turn small from basic,when checked with a master gage. The maximum wearon a working ring gage shall not be more than 1⁄4 turnlarge from basic, when checked with a master gage. Asupplementary check by optical or other means shouldbe made of flank angle and form.
7.4 Relation of Lead and Angle Variations to PitchDiameter Tolerances of Gages
When it is necessary to compute from measurementsthe decimal part of a turn that a gage varies from thebasic dimensions, Tables 10 and 11 should be used.Table 10 gives the correction in diameter for angle varia-tions, and Table 11 gives the correction in diameter forlead variations. These corrections are always added tothe pitch diameter in the case of external threads andsubtracted in the case of internal threads, regardless ofwhether the lead or angle variations are either plus orminus. The diameter equivalent for lead and angle varia-tions plus the pitch diameter variation multiplied by 16gives the longitudinal variation from basic at the gagingnotch. This longitudinal variation divided by the pitchequals the decimal part of a turn that the gage variesfrom basic at the gaging notch.
Copyright ASME International Provided by IHS under license with ASME Licensee=CTCI Corporation/5926309001, User=Wang, Hsien Yu
Not for Resale, 12/26/2013 16:53:44 MSTNo reproduction or networking permitted without license from IHS
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ASME B1.20.1-2013
Fig. 7 NPT Standard Taper Pipe Thread Plug and Ring Gages
Plug gage
Notch
L1
L1
E0
E1
Ring gage
L2
Taper of thread 1 in 16 measured on diameter
20
Copyright ASME International Provided by IHS under license with ASME Licensee=CTCI Corporation/5926309001, User=Wang, Hsien Yu
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ASME B1.20.1-2013
Fig. 8 Suggested Form of Gage Thread
Crests truncated Crests truncated
Roots sharp or undercut (form optional)
Ring gage
Plug gage
0.116P
GENERAL NOTE: Roots must clear 0.0381P width.
21
Copyright ASME International Provided by IHS under license with ASME Licensee=CTCI Corporation/5926309001, User=Wang, Hsien Yu
Not for Resale, 12/26/2013 16:53:44 MSTNo reproduction or networking permitted without license from IHS
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ASME B1.20.1-2013
Tabl
e8
Bas
icD
imen
sion
sof
Thre
aded
Gag
esfo
rAm
eric
anN
atio
nal
Stan
dard
Tape
rPi
peTh
read
s,N
PT
Min
orD
iam
eter
sof
Rin
gM
ajor
Dia
met
ers
ofPl
ugan
dIn
tern
alPi
tch
Dia
met
ers
ofPl
ug,
Rin
g,an
dan
dEx
tern
alIn
dica
ting
Indi
cati
ngG
ages
Indi
cati
ngG
ages
[Not
e(1
)]G
ages
Thic
knes
sof
Incr
ease
inN
omin
alA
tS
mal
lA
tG
agin
gA
tLa
rge
At
Sm
all
At
Gag
ing
At
Larg
eA
tS
mal
lA
tG
agin
gL 1
Rin
gor
Dia
./Th
read
Pipe
O.D
.of
Thre
ads/
End,
E 0N
otch
,E 1
End,
E 2En
d,E 0
Not
ch,
E 1En
d,E 2
End,
E 0N
otch
,E 1
Gag
eS
ize
Pipe
,D
Inch
,n
Pitc
h,P
Plan
ePl
ane
Plan
ePl
ane
Plan
ePl
ane
Plan
ePl
ane
0.06
25/n
Elem
ents
12
34
56
78
910
1112
1314
1 ⁄ 16
0.31
2527
.00.
0370
3704
0.29
289
0.30
289
0.30
920
0.27
118
0.28
118
0.28
750
0.24
948
0.25
948
0.00
231
0.16
001 ⁄ 8
0.40
5027
.00.
0370
3704
0.38
521
0.39
531
0.40
171
0.36
351
0.37
360
0.38
000
0.34
180
0.35
190
0.00
231
0.16
151 ⁄ 4
0.54
0018
.00.
0555
5556
0.51
339
0.52
763
0.53
850
0.47
739
0.49
163
0.50
250
0.44
139
0.45
563
0.00
347
0.22
783 ⁄ 8
0.67
5018
.00.
0555
5556
0.64
802
0.66
302
0.67
350
0.61
201
0.62
701
0.63
750
0.57
601
0.59
101
0.00
347
0.24
001 ⁄ 2
0.84
0014
.00.
0714
2857
0.80
600
0.82
600
0.83
936
0.75
843
0.77
843
0.79
178
0.71
086
0.73
086
0.00
446
0.32
00
3 ⁄ 41.
0500
14.0
0.07
1428
571.
0152
51.
0364
41.
0493
60.
9676
80.
9888
71.
0017
80.
9201
10.
9412
90.
0044
60.
3390
11.
3150
11.5
0.08
6956
521.
2715
51.
2965
51.
3142
21.
2136
31.
2386
31.
2563
11.
1557
21.
1807
20.
0054
30.
4000
11 ⁄ 41.
6600
11.5
0.08
6956
521.
6150
51.
6413
01.
6592
21.
5571
31.
5833
81.
6013
11.
4992
21.
5254
70.
0054
30.
4200
11 ⁄ 21.
9000
11.5
0.08
6956
521.
8540
01.
8802
51.
8992
21.
7960
91.
8223
41.
8413
11.
7381
71.
7644
20.
0054
30.
4200
22.
3750
11.5
0.08
6956
522.
3269
42.
3541
92.
3742
22.
2690
22.
2962
72.
3163
02.
2111
12.
2383
60.
0054
30.
4360
21 ⁄ 22.
8750
8.0
0.12
5000
002.
8027
82.
8454
12.
8738
82.
7195
32.
7621
62.
7906
32.
6362
82.
6789
00.
0078
10.
6820
33.
5000
8.0
0.12
5000
003.
4238
83.
4717
53.
4988
83.
3406
33.
3885
03.
4156
33.
2573
73.
3052
50.
0078
10.
7660
31 ⁄ 24.
0000
8.0
0.12
5000
003.
9207
53.
9720
73.
9988
83.
8375
03.
8888
13.
9156
33.
7542
53.
8055
60.
0078
10.
8210
44.
5000
8.0
0.12
5000
004.
4176
34.
4703
84.
4988
84.
3343
84.
3871
34.
4156
34.
2511
24.
3038
70.
0078
10.
8440
55.
5630
8.0
0.12
5000
005.
4739
85.
5325
55.
5618
85.
3907
35.
4492
95.
4786
35.
3074
85.
3660
40.
0078
10.
9370
66.
6250
8.0
0.12
5000
006.
5293
56.
5892
26.
6238
86.
4460
96.
5059
76.
5406
36.
3628
46.
4227
20.
0078
10.
9580
88.
6250
8.0
0.12
5000
008.
5168
58.
5832
88.
6238
88.
4335
98.
5000
38.
5406
38.
3503
48.
4167
80.
0078
11.
0630
1010
.750
08.
00.
1250
0000
10.6
2857
10.7
0419
10.7
4888
10.5
4531
10.6
2094
10.6
6563
10.4
6206
10.5
3768
0.00
781
1.21
0012
12.7
500
8.0
0.12
5000
0012
.616
0712
.701
0712
.748
8812
.532
8112
.617
8112
.665
6312
.449
5612
.534
560.
0078
11.
3600
1414
.000
08.
00.
1250
0000
13.8
5825
13.9
5588
13.9
9888
13.7
7500
13.8
7263
13.9
1563
13.6
9175
13.7
8937
0.00
781
1.56
20
1616
.000
08.
00.
1250
0000
15.8
4575
15.9
5900
15.9
9888
15.7
6250
15.8
7575
15.9
1563
15.6
7925
15.7
9250
0.00
781
1.81
2018
18.0
000
8.0
0.12
5000
0017
.833
2517
.958
2517
.998
8817
.750
0017
.875
0017
.915
6317
.666
7517
.791
750.
0078
12.
0000
2020
.000
08.
00.
1250
0000
19.8
2075
19.9
5357
19.9
9888
19.7
3750
19.8
7031
19.9
1563
19.6
5425
19.7
8706
0.00
781
2.12
5024
24.0
000
8.0
0.12
5000
0023
.795
7523
.944
1923
.998
8823
.712
5023
.860
9423
.915
6323
.629
2523
.777
680.
0078
12.
3750
GEN
ERA
LN
OTE
:G
age
blan
kssh
allc
onfo
rmto
dim
ensi
ons
give
nin
ASM
EB
47.1
.Th
em
ajor
diam
eter
sof
inte
rnal
thre
adga
ges
and
the
min
ordi
amet
ers
ofex
tern
alth
read
gage
sar
eba
sed
upon
the
trun
cati
ons
spec
ified
inpa
ra.
7.2.
NO
TE:
(1)
The
pitc
hdi
amet
erat
the
larg
een
d,E 2
,do
esno
tap
ply
tori
ngga
ges.
22
Copyright ASME International Provided by IHS under license with ASME Licensee=CTCI Corporation/5926309001, User=Wang, Hsien Yu
Not for Resale, 12/26/2013 16:53:44 MSTNo reproduction or networking permitted without license from IHS
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ASME B1.20.1-2013
Tabl
e9
Wor
king
Gag
eTo
lera
nces
for
Amer
ican
Nat
iona
lS
tand
ard
Tape
rPi
peTh
read
,N
PT
Sta
ndof
fB
etw
een
Plug
and
Ring
Tole
ranc
eon
Tole
ranc
eTo
lera
nce
Gag
esat
Gag
ing
Hal
fA
ngle
,4To
lera
nce
onon
Maj
oron
Min
orTo
tal
Cum
ulat
ive
Tole
ranc
eN
otch
for
Tole
ranc
eon
Min
utes
Tape
r,3,
5D
ia.
Dia
.To
lera
nces
onN
omin
alO
.D.
ofon
Pitc
hD
imen
sion
sat
Lead
2,3
Pitc
hD
ia.
Pipe
Pipe
,D
ia.,1
Plug
s,R
ings
,Pl
ugs,
Ring
s,Pl
ugs,
Ring
s,O
ppos
ite
Extr
eme
Siz
eD
Thre
ads/
Inch
±Pl
ugs
Rin
gs±
±+
−−
+Pl
ugs
Ring
sTo
lera
nce
Lim
its6
12
34
56
78
910
1112
1314
15
1 ⁄ 16
0.31
2527
0.00
020.
0002
0.00
0315
200.
0003
0.00
060.
0004
0.00
040.
0008
00.
0011
80.
032
1 ⁄ 80.
405
270.
0002
0.00
020.
0003
1520
0.00
030.
0006
0.00
040.
0004
0.00
080
0.00
118
0.03
21 ⁄ 4
0.54
018
0.00
020.
0002
0.00
0315
200.
0004
0.00
070.
0006
0.00
060.
0009
20.
0013
40.
036
3 ⁄ 80.
675
180.
0002
0.00
020.
0003
1520
0.00
040.
0007
0.00
060.
0006
0.00
092
0.00
134
0.03
61 ⁄ 2
0.84
014
0.00
030.
0002
0.00
0310
150.
0006
0.00
090.
0010
0.00
100.
0009
70.
0014
20.
038
3 ⁄ 41.
050
140.
0003
0.00
020.
0003
1015
0.00
060.
0009
0.00
100.
0010
0.00
097
0.00
142
0.03
81
1.31
511
.50.
0003
0.00
030.
0004
1015
0.00
080.
0012
0.00
100.
0010
0.00
121
0.00
170
0.04
711 ⁄ 4
1.66
011
.50.
0003
0.00
030.
0004
1015
0.00
080.
0012
0.00
100.
0010
0.00
121
0.00
170
0.04
711 ⁄ 2
1.90
011
.50.
0003
0.00
030.
0004
1015
0.00
080.
0012
0.00
100.
0010
0.00
121
0.00
170
0.04
72
2.37
511
.50.
0003
0.00
030.
0004
1015
0.00
080.
0012
0.00
100.
0010
0.00
121
0.00
170
0.04
7
21 ⁄ 22.
875
80.
0005
0.00
040.
0005
710
0.00
100.
0014
0.00
160.
0016
0.00
158
0.00
211
0.05
93
3.50
08
0.00
050.
0004
0.00
057
100.
0010
0.00
140.
0016
0.00
160.
0015
80.
0021
10.
059
31 ⁄ 24.
000
80.
0005
0.00
040.
0005
710
0.00
100.
0014
0.00
160.
0016
0.00
158
0.00
211
0.05
94
4.50
08
0.00
050.
0004
0.00
057
100.
0010
0.00
140.
0016
0.00
160.
0015
80.
0021
10.
059
55.
563
80.
0005
0.00
040.
0005
710
0.00
100.
0014
0.00
160.
0016
0.00
158
0.00
211
0.05
9
66.
625
80.
0005
0.00
040.
0005
710
0.00
100.
0014
0.00
160.
0016
0.00
158
0.00
211
0.05
98
8.62
58
0.00
050.
0004
0.00
057
100.
0010
0.00
140.
0020
0.00
200.
0015
80.
0021
10.
059
1010
.750
80.
0005
0.00
040.
0005
710
0.00
100.
0014
0.00
200.
0020
0.00
158
0.00
211
0.05
912
12.7
508
0.00
050.
0004
0.00
057
100.
0010
0.00
140.
0020
0.00
200.
0015
80.
0021
10.
059
140.
D.
14.0
008
0.00
080.
0005
0.00
067
100.
0010
0.00
140.
0030
0.00
300.
0020
60.
0027
10.
076
160.
D.
16.0
008
0.00
080.
0005
0.00
067
100.
0010
0.00
140.
0030
0.00
300.
0020
60.
0027
10.
076
180.
D.
18.0
008
0.00
080.
0005
0.00
067
100.
0010
0.00
140.
0030
0.00
300.
0020
60.
0027
10.
076
200.
D.
20.0
008
0.00
080.
0005
0.00
067
100.
0010
0.00
140.
0030
0.00
300.
0020
60.
0027
10.
076
240.
D.
24.0
008
0.00
080.
0005
0.00
067
100.
0010
0.00
140.
0030
0.00
300.
0020
60.
0027
10.
076
23
Copyright ASME International Provided by IHS under license with ASME Licensee=CTCI Corporation/5926309001, User=Wang, Hsien Yu
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ASME B1.20.1-2013
Tabl
e9
Wor
king
Gag
eTo
lera
nces
for
Amer
ican
Nat
iona
lS
tand
ard
Tape
rPi
peTh
read
,N
PT(C
ont’
d)
GEN
ERA
LN
OTE
S:
(a)
The
larg
een
dof
the
mas
ter
ring
gage
shal
lbe
flush
wit
hth
ega
ging
notc
hof
its
mas
ter
plug
whe
nas
sem
bled
hand
tigh
tw
ithi
n±0
.002
for
size
s1 ⁄ 1
6to
2,in
clus
ive,
wit
hin
±0.0
03fo
rsi
zes
21 ⁄ 2to
12,
incl
usiv
e,an
dw
ithi
n±0
.005
for
size
s14
and
larg
er.
(b)
The
tole
ranc
esfo
rth
ele
ngth
L 1fr
omsm
all
end
toga
ging
notc
hof
the
plug
gage
d(F
ig.
4)sh
all
be+0
.000
and
−0.
001
for
size
s1 ⁄ 1
6to
2,in
clus
ive,
and
+0.0
00an
d−
0.00
2fo
rsi
zes
21 ⁄ 2an
dla
rger
.(c
)Th
eto
lera
nces
for
the
over
all
thre
adle
ngth
L 2of
the
plug
gage
(Fig
.4)
shal
lbe
+0.0
50an
d−
0.00
0fo
ral
lsi
zes.
(d)
Tole
ranc
esfo
rth
eth
ickn
ess
L 1of
the
ring
gage
(Fig
.4)
shal
lbe
−0.
000
and
+0.0
01fo
rsi
zes
1 ⁄ 16
to2,
incl
usiv
e,an
d−
0.00
0an
d+0
.002
for
size
s2
1 ⁄ 2an
dla
rger
.
NO
TES
:(1
)To
bem
easu
red
atth
ega
ging
notc
hof
plug
gage
.(2
)A
llow
able
vari
atio
nin
lead
betw
een
any
two
thre
ads
inL 1
leng
thof
gage
(Fig
.4)
.(3
)Th
ele
adan
dta
per
onpl
ugan
dri
ngga
ges
shal
lbe
mea
sure
dal
ong
the
pitc
hlin
eom
itti
ngth
eim
perf
ect
thre
ads
atea
chen
d.(4
)In
solv
ing
for
the
corr
ecti
onin
diam
eter
for
angl
ede
viat
ions
,th
eav
erag
ede
viat
ion
inha
lfan
gle
for
the
two
side
sof
thre
ad,
rega
rdle
ssof
thei
rsi
gns,
shou
ldbe
take
n.(5
)A
llow
able
vari
atio
nin
tape
rin
L 1le
ngth
ofga
ge(F
ig.
4).
(6)
Max
imum
poss
ible
inte
rcha
nge
stan
doff
,an
yri
ngag
ains
tan
ypl
ugot
her
than
its
mas
ter
plug
,m
ayoc
cur
whe
nta
per
devi
atio
nsar
eze
roan
dal
lot
her
dim
ensi
ons
are
atop
posi
teex
trem
eto
lera
nce
limit
s.A
vera
gest
ando
ffsh
ould
bew
ell
wit
hin
thes
em
axim
umlim
its.
24
Copyright ASME International Provided by IHS under license with ASME Licensee=CTCI Corporation/5926309001, User=Wang, Hsien Yu
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ASME B1.20.1-2013
Table 10 Diameter Equivalent of Variation in Half Included Angle of Thread for Tools and Gages
Variation1 in Half Angle(in Minutes) 8 Threads/Inch 11.5 Threads/Inch 14 Threads/Inch 18 Threads/Inch 27 Threads/Inch
1 2 3 4 5 6
1 0.0000559 0.0000389 0.0000320 0.0000249 0.00001662 0.0001119 0.0000778 0.0000639 0.0000497 0.00003313 0.0001678 0.0001167 0.0000959 0.0000746 0.00004974 0.0002237 0.0001556 0.0001278 0.0000994 0.00006635 0.0002796 0.0001945 0.0001598 0.0001243 0.0000829
6 0.0003356 0.0002334 0.0001917 0.0001491 0.00009947 0.0003915 0.0002723 0.0002237 0.0001740 0.00011608 0.0004474 0.0003112 0.0002557 0.0001989 0.00013269 0.0005033 0.0003502 0.0002876 0.0002237 0.0001491
10 0.0005593 0.0003891 0.0003196 0.0002486 0.0001657
11 0.0006152 0.0004280 0.0003515 0.0002734 0.000182312 0.0006711 0.0004669 0.0003835 0.0002983 0.000198913 0.0007271 0.0005058 0.0004155 0.0003231 0.000215414 0.0007830 0.0005447 0.0004474 0.0003480 0.000232015 0.0008389 0.0005836 0.0004794 0.0003729 0.0002486
16 0.0008948 0.0006225 0.0005113 0.0003977 0.000265117 0.0009508 0.0006614 0.0005433 0.0004226 0.000281718 0.0010067 0.0007003 0.0005753 0.0004474 0.000298319 0.0010626 0.0007392 0.0006072 0.0004723 0.000314920 0.0011186 0.0007781 0.0006392 0.0004971 0.0003314
21 0.0011745 0.0008170 0.0006711 0.0005220 0.000348022 0.0012304 0.0008559 0.0007031 0.0005469 0.000364623 0.0012863 0.0008949 0.0007351 0.0005717 0.000381124 0.0013423 0.0009338 0.0007670 0.0005966 0.000397725 0.0013982 0.0009727 0.0007990 0.0006214 0.0004143
26 0.0014541 0.0010116 0.0008309 0.0006463 0.000430927 0.0015101 0.0010505 0.0008629 0.0006711 0.000447428 0.0015660 0.0010894 0.0008949 0.0006960 0.000464029 0.0016219 0.0011283 0.0009268 0.0007209 0.000480630 0.0016779 0.0011672 0.0009588 0.0007457 0.0004971
45 0.0025169 0.0017509 0.0014382 0.0011186 0.000745750 0.0027966 0.0019454 0.0015980 0.0012429 0.0008286
GENERAL NOTES:(a) Values given in inches at 68°F.(b) In solving for the diameter equivalent of angle variations, the average variation in half included angle for the two sides of the thread,
regardless of their signs, should be taken.(c) Table is based upon an NPT gage with 0.100P root/crest truncations with equal half-angle variations. For other gages with equal
truncations, multiply by0.86600P − 2 (truncation)
0.66666667PNOTE:(1) Diameter equivalent p 1.53811978P tan ��, where �� p variation in half included angle of thread expressed in minutes.
25
Copyright ASME International Provided by IHS under license with ASME Licensee=CTCI Corporation/5926309001, User=Wang, Hsien Yu
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ASME B1.20.1-2013
Tabl
e11
Dia
met
erEq
uiva
lent
ofVa
riat
ion
inLe
adfo
rTo
ols
and
Gag
es
Vari
atio
n,�
P0.
0000
00.
0000
10.
0000
20.
0000
30.
0000
40.
0000
50.
0000
60.
0000
70.
0000
80.
0000
9
12
34
56
78
910
11
0.00
000
0.00
0000
00.
0000
173
0.00
0034
60.
0000
520
0.00
0069
30.
0000
866
0.00
0103
90.
0001
212
0.00
0138
60.
0001
559
0.00
010
0.00
0173
20.
0001
905
0.00
0207
80.
0002
252
0.00
0242
50.
0002
598
0.00
0277
10.
0002
944
0.00
0311
80.
0003
291
0.00
020
0.00
0346
40.
0003
637
0.00
0381
00.
0003
984
0.00
0415
70.
0004
330
0.00
0450
30.
0004
676
0.00
0485
00.
0005
023
0.00
030
0.00
0519
60.
0005
369
0.00
0554
20.
0005
716
0.00
0588
90.
0006
062
0.00
0623
50.
0006
408
0.00
0658
20.
0006
755
0.00
040
0.00
0692
80.
0007
101
0.00
0727
40.
0007
448
0.00
0762
10.
0007
794
0.00
0796
70.
0008
140
0.00
0831
40.
0008
487
0.00
050
0.00
0866
00.
0008
833
0.00
0900
60.
0009
180
0.00
0935
30.
0009
526
0.00
0969
90.
0009
872
0.00
1004
60.
0010
219
0.00
060
0.00
1039
20.
0010
565
0.00
1073
80.
0010
912
0.00
1108
50.
0011
258
0.00
1143
10.
0011
604
0.00
1177
80.
0011
951
0.00
070
0.00
1212
40.
0012
297
0.00
1247
00.
0012
644
0.00
1281
70.
0012
990
0.00
1316
30.
0013
336
0.00
1351
00.
0013
683
0.00
080
0.00
1385
60.
0014
029
0.00
1420
20.
0014
376
0.00
1454
90.
0014
722
0.00
1489
50.
0015
068
0.00
1524
20.
0015
415
0.00
090
0.00
1558
80.
0015
761
0.00
1593
40.
0016
108
0.00
1628
10.
0016
454
0.00
1662
70.
0016
800
0.00
1697
40.
0017
147
0.00
100
0.00
1732
00.
0017
493
0.00
1766
60.
0017
840
0.00
1801
30.
0018
186
0.00
1835
90.
0018
532
0.00
1870
60.
0018
879
0.00
110
0.00
1905
20.
0019
225
0.00
1939
80.
0019
572
0.00
1974
50.
0019
918
0.00
2009
10.
0020
264
0.00
2043
80.
0020
611
0.00
120
0.00
2078
40.
0020
957
0.00
2113
00.
0021
304
0.00
2147
70.
0021
650
0.00
2182
30.
0021
996
0.00
2217
00.
0022
343
0.00
130
0.00
2251
60.
0022
689
0.00
2286
20.
0023
036
0.00
2320
90.
0023
382
0.00
2355
50.
0023
728
0.00
2390
20.
0024
075
0.00
140
0.00
2424
80.
0024
421
0.00
2459
40.
0024
768
0.00
2494
10.
0025
114
0.00
2528
70.
0025
460
0.00
2563
40.
0025
807
0.00
150
0.00
2598
00.
0026
153
0.00
2632
60.
0026
500
0.00
2667
30.
0026
846
0.00
2701
90.
0027
192
0.00
2736
60.
0027
539
0.00
160
0.00
2771
20.
0027
885
0.00
2805
80.
0028
232
0.00
2840
50.
0028
578
0.00
2875
10.
0028
924
0.00
2909
80.
0029
271
0.00
170
0.00
2944
40.
0029
617
0.00
2979
00.
0029
964
0.00
3013
70.
0030
310
0.00
3048
30.
0030
656
0.00
3083
00.
0031
003
0.00
180
0.00
3117
60.
0031
349
0.00
3152
20.
0031
696
0.00
3186
90.
0032
042
0.00
3221
50.
0032
388
0.00
3256
20.
0032
735
0.00
190
0.00
3290
80.
0033
081
0.00
3325
40.
0033
428
0.00
3360
10.
0033
774
0.00
3394
70.
0034
120
0.00
3429
40.
0034
467
0.00
200
0.00
3464
00.
0034
813
0.00
3498
60.
0035
160
0.00
3533
30.
0035
506
0.00
3567
90.
0035
852
0.00
3602
60.
0036
199
GEN
ERA
LN
OTE
S:
(a)
Valu
esgi
ven
inin
ches
at68
°F.
(b)
Dia
met
ereq
uiva
lent
p1.
7320
5081
�P,
whe
re�P
pva
riat
ion
inle
adbe
twee
nan
ytw
oth
read
s.
26
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ASME B1.20.1-2013
NONMANDATORY APPENDIX ATHE TURNS OF ENGAGEMENT METHOD OF GAGING
PRODUCT THREADS
A-1 METHOD OF GAGING
The turns of engagement method of gaging taperthreads determines that there is an adequate numberof threads available at hand engagement. This methodeliminates the effects of product chamfers during gaging.However, differences between gages’ end threadremoval and gage crest truncations may give differentgaging results for the same product thread. This maynecessitate collaboration between supplier and user.
27
A-2 TOLERANCE
The theoretical basic turns of engagement are foundin column 7 of Table 2. For the turns of engagementmethod, the turns to remove the L1 gage from the productthread are counted and must be within the tolerance ofbasic number of turns, ±1 turn.
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ASME B1.20.1-2013
NONMANDATORY APPENDIX BTAP DRILL SIZES
Holes prepared for tapping can be either straight ortapered. Both are acceptable as long as the product stan-dards for thread dimensions are met after tapping. Theminor diameter of the product threads should be cut bythe tap minor diameter to ensure concentricity with thepitch diameter, as well as to generate the proper threadheight and truncations. The actual hole size prior totapping is dependent on many variables and shouldapproximate the diameter K0, column 24 of Table 2 (BasicMinor Diameter at Small End of Pipe). Hole sizes mayvary from K0 so the tap can cut an acceptable pipe threadwith the required thread height.
28
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ASME B1.20.1-2013
NONMANDATORY APPENDIX CTHREAD TYPES AND CORRESPONDING GAGES AND GAGING
See Table C-1.
Table C-1 Thread Types and Corresponding Gages and Gaging
Product Thread Tolerance Applied to Basic Size
Thread External InternalThread to Type ofBe Gaged Thread Internal External Gaged With Small Large Large Small
NPT Pressure Taper Taper L1 or indicating gages 1 Turn 1 Turn 1 Turn 1 Turn
NPSC Pressure Straight . . . L1 or indicating gages . . . . . . 11⁄2 Turns 11⁄2 Turns
NPTR Mechanical Taper Taper L1 or indicating gages 1 Turn 0 Turns 1 Turn 0 Turns[Note (1)] [Note (1)] [Note (2)] [Note (2)]
NPSM Mechanical Straight Straight GO/NOT GO or indicating gages . . . . . . . . . . . .
NPSL Mechanical Straight Straight GO/NOT GO or indicating gages . . . . . . . . . . . .
NOTES:(1) See Table 5, column 7 for the modified external thread basic position.(2) See Table 5, column 18 for the internal thread basic position below the face of the fitting.
29
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INTENTIONALLY LEFT BLANK
30
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Not for Resale, 12/26/2013 16:53:44 MSTNo reproduction or networking permitted without license from IHS
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ASME B1.20.1-2013
N10313Copyright ASME International Provided by IHS under license with ASME Licensee=CTCI Corporation/5926309001, User=Wang, Hsien Yu
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