working drawings and assemblies

7/29/2019 Working Drawings and Assemblies

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Working Drawing and

Assemblies

Chapter 10


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Objectives

1.Define working drawings.

2. Describe how working drawings are used inindustry.

3. List the major components of a complete setof working drawings.

4. Describe the differences between detail andassembly drawings.

5. Describe how part numbers, zoning, andtables are used on working drawings.

6. Draw standard representation of threads.


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Objectives

7. Specify a metric or English thread in a note.

8. Use the graphic language of mechanisms

such as gears, cams, bearings, and linkages.

9. Interpret the specialized graphic language

used in piping and welding drawings.

10. Describe how CAD is used to create, store,

and retrieve working drawings.

11. List techniques used to create copies of

engineering drawings.


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Working Drawings

Working drawings are the

complete set of standardized

drawings specifying the

manufacture and assembly of a

product based on its design.


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Working Drawings

The complexity of the design

determines the number and types

of drawings.Working drawings may be on more

than one sheet and may contain

written instructions calledspecifications.


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Working Drawings

Working drawings are the blueprints

used for manufacturing products.

Therefore, the set of drawings must: completely describe the parts, both visually

and dimensionally

show the parts in assembly

identify all the parts

specify standard parts.


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Working Drawings

A complete set of working drawings for

an assembly include:

detail drawings of each nonstandard part. an assembly or subassembly drawing

showing all the standard and nonstandard

parts in a single drawing.

a bill of materials (BOM). a title block.


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Detail Drawings

A detail drawing is a dimensioned,

multiview drawing of a single part,

describing the parts shape, size,material, and finish, in sufficient

detail for the part to be

manufactured based on the drawingalone.


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Assembly Drawings

An assembly drawing shows how

each part of a design is put

together. If the design depicted isonly part of the total assembly, it is

referred to as a subassembly.


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Assembly Drawings

An assembly drawing normally consists of:

All the parts, drawn in their operating position.

A parts list orbill of materials (BOM) shows the

detail number for each part, the quantity needed fora single assembly the description or name of thepart, the catalog number if it is a standard part, andthe company part number.

Leader lines with balloons, assigning each part a

detail number, in sequential order and keyed tothe list of parts in the parts list.

Machining and assembly operations and criticaldimensions related to these functions.


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Assembly Drawings

Types

outline assembly gives a general

graphic description of the exteriorshape. Outline assemblies are used

for parts catalogs and installation

manuals or for production when the

assembly is simple enough to bevisualized without the use of other

drawings.


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Assembly Drawings

Types

sectioned assembly gives a general

graphic description of the interiorshape by passing a cutting plane

through all or part of the assembly.

Sectioned assembly drawings are

used for the manufacture andassembly of complicated devices.


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Assembly Drawings


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Assembly Drawings

Types

pictorial assembly gives a general

graphic description of each part, anduses center lines to show how the

parts are assembled.


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Part and Drawing Numbers

A part number is usually a string of numbers

coded in such a way that a company can keep

accurate records of its products.

Drawing number: Each company develops its

own standard numbering system, based on

various criteria such as sequential numbers,

combinations of numbers and letters, sheet

sizes, number of parts in the assembly, modelnumbers, function, etc.


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Title Blocks

Title blocks are used to record all theimportant information necessary for the workingdrawings. The title block is normally located in

the lower right corner of the drawing sheet. Title blocks should contain the following:

Name and address of the company ordesign activity.

Title of the drawing. Drawing number.

Names and dates of the drafters, checker,issue date, contract number, etc.


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Title Blocks

Design approval, when subcontractors areused.

Additional approval block.

Predominant drawing scale.

Federal supply code for manufacturers(FSCM) number.

Drawing sheet size letter designation.

Actual or estimated weight of the item.

Sheet number, if there are multiple sheetsin the set.


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Parts Lists

A complete set of working drawings

must include a detailed parts list or

bill of material. Based on ANSIstandards, a parts list should be

located in the lower right corner

above the title block.


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Parts Lists

The information normally included in a parts list

is as follows:

Name of the part.

A detail number for the part in the assembly.

The part material, such as cast iron or bronze.

The number of times that part is used in the

assembly.

The company-assigned part number.

Other in formation, such as weight, stock size,

etc.


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Revision Blocks

When a drawing is revised because of design

changes, errors, etc., an accurate record of the

change should be created.

This information includes:

the person making the change

description of the change

the change number approval for the change


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Engineering Changes Order

Used to make changes in a design.

Most industries require the use of

engineering change notice (ECN).Common features includes;

Identification of what has to be

changed in the form of part numbers,part names, and drawing numbers.


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Engineering Changes Order

An explanation of the need for the

requested changed.

A list of all documents anddepartments affected by the change.

Approval by the projects managers

Instruction describing when thechanges are to be implemented.


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Scale and Tolerance Specs.

The designations METRIC or SI appear in or

near the title block to show that metric

dimensions and scale are used on the drawing.

A graphics scale can also be used, especiallyon mapping drawings.

Tolerances are specified in a drawing using

toleranced dimensions. For those dimensions

that are not specifically toleranced, a generaltolerance note is used.


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Zones and Tabular Drawing

Zones are used on large sheets for

reference purposes. Zones in

engineering drawing are similar to thezones used on highway maps.

Tabular drawings are used when

several similar parts have common

features. Such parts can be groupedtogether into a family of parts.


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Working Assembly Drawing

A working assembly drawing, also

known as a detailed assembly,

combines on a single sheet the detaildrawing and the assembly drawing,

usually a section view. Such drawings

are used for relatively simple assemblies

that use some standard parts.


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Threaded Fastener

Fastening is a method of connecting or

joining two or more parts together, using

processes or devices.One of the most common methods used

for fastening is mechanical fastening, a

process that uses manufactured devices

such as screws, pins, or rivets to holdparts of an assembly together.


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Thread Terminology

Axis

Chamfer

Crest

Depth

Die

External thread

Internal thread

Lead

Major Diameter

Minor Diameter

Pitch

Pitch diameter

Root

Screw thread

Side

Tap

Thread: angle, form,series

Thread per inch


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Thread Specification

English system

Thread form - the profile or shape of a thread cutinto a cylinder.

Sharp-VAmerican National

Unified

Unified National Round

Metric

Acme Square

Knuckle

Buttress


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English system

Series - the number of threads per inch for a given

diameter.

Coarse quick assembly or disassembly of castiron, soft metals, and plastic. NC or UNC.

Fine - fasteners are used when a great deal of

force is necessary for assembly, and are

designated NF or UNF.

Extra fine - fasteners are used when the length ofengagement is short and the application calls for

high degrees of stress.


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English system

Class

Class 1-a loose fit where quick assembly is

required and looseness or play between partsis acceptable.

Class 2-a high-quality, general purpose,commercial class of fit for bolts, nuts, andscrews widely used in mass production.

Class 3-a very high-quality threaded fastenerwith a close fit, used for precision tools andfor high stress and vibration applications.


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Threaded Specification

English system

Note

Major diameterNumber of threads

Form

Series

Class Internal or external

Qualifying information


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Metric system

A complete metric thread note should

contain the following information, in theorder given:

Thread form symbol- The letter M is used to

designate the metric profile. The J profile

class is a modified M profile.

Nominal size (basic major diameter)

Pitch

General purpose tolerance


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Thread Drawings

Three conventional methods:

Detailed

Schematics Simplified


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Standard Bolts, Stud and

ScrewGeneral types of standard threaded

fastener:

Bolt - a mechanical threaded device with a

head on one end and threads on the otherend. Bolts are paired with nuts. A nut is amechanical threaded device used on theend of a bolt, a stud, or a machine screw.

Stud - a rod that is threaded on both endsand joins two mating parts. A nut may beused on one end.


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Screw

Cap screw - a mechanical threadeddevice with a head on one end and threads

on the other end. Cap screws join twomating parts and have longer threads thanbolts.

Machine screw - a mechanical threaded

device with a head on one end and threadson the other end. The threaded end mayscrew into a mating part, or may be usedwith a nut.


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Screw

Set screw - a mechanical threaded device

with or without a head, used to prevent

rotation or movement between parts, such

as a shaft and a collar.


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Nonthreaded Fastener

Nonthreaded fasteners are mechanical

devices generally used to prevent motion

between mating parts. Dowels

Pins dowel, straight, tapered, groove

Key plain, gib head, Woodruff, P&W

Rivet

Retaining rings


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Springs

Mechanical devices that expand or

contract due to pressure or force.

Compression Tension

Extension

Flat

Constant force


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Mechanism

A machine is a combination of interrelated

parts for using or applying energy to do work.

Gears - transmit rotational power and motion

between portions of a mechanism. Cams - used to translate rotational motion into

linear motion.

Linkages - the most common type of mechanism in

use to transmit force. A linkage consists of a

(usually) linear element, called the bar, and one or

twojoints.


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Mechanism

Bearings - used in conjunction with other

mechanisms such as gears and

linkages to minimize friction and wear

between the parts.

Plain

Rolling contact


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Welding

Welding drawings are a specialized

type of technical drawing which differs

from many other types of drawings in

that its main focus is to specify how parts

are joined together. Since welds are both

permanent and structural, proper

location and orientation of the weldedmembers and the type of weld used are

important to properly specify.


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Welding

Eight basic parts;

Reference line

Leader line and arrow

Basic weld symbol (location and depth of weld)

Finish symbol

Weld symbol (type of weld)

Dimensions

Supplementary symbols Tail and specifications


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Reprographics

Refers to the technology and techniques of

reproducing documents. After the engineering

drawings have been created they are copied for

others to use, carefully stored, and set up foreasy future accessibility.

After the original drawing is created, it must be

carefully stored or archived. The process used

to store and retrieve engineering drawings iscalled archiving.


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Reprographics

Techniques

Blueprinting

Diazo Xerography

Microfilming

Digital

Scanning

Storage CAD

working drawings and assemblies

Documents