Thread Notation

Coordinate Dimensioning Table of ContentsReturn to the Previous Slide Slide 1 QuitMaster Table of ContentsGlossary

86

57.656.6

100 99

9.69.4

25.525.4

3634

41.341.1

20.00 - 20.13

0.14 A C

B

M42 X 1.5 - 6g

0.1 M B M

0.06 A

6.66.1

9.69.4

44.6044.45

0.08 M A

C

A

0.02

31.831.6

0.1 B

8X 7.9 - 8.1

8X 45°

0.14 M A C M

44Engineering Graphics PrinciplesEngineering Graphics Principles Copyright © 2002

Brigham Young UniversityAll Rights Reserved

CoordinateCoordinateDimensioning andDimensioning and

TolerancingTolerancing

UnitUnit


86

57.656.6

100 99

9.69.4

25.525.4

3634

41.341.1

20.00 - 20.13

0.14 A C

B

M42 X 1.5 - 6g

0.1 M B M

0.06 A

6.66.1

9.69.4

44.6044.45

0.08 M A

C

A

0.02

31.831.6

0.1 B

8X 7.9 - 8.1

8X 45°

0.14 M A C M

COORDINATE DIMENSIONING and

TOLERANCINGBasic Thread Notation

COORDINATE DIMENSIONING and

TOLERANCINGBasic Thread Notation

ENGINEERINGENGINEERING GRAPHICSGRAPHICS


REPRESENTING AND DIMENSIONING REPRESENTING AND DIMENSIONING SCREW THREADSSCREW THREADS


Basic Dimensioning Guidelines and RulesBasic Dimensioning Guidelines and Rules

Representing and Dimensioning Screw ThreadsRepresenting and Dimensioning Screw Threads

Screw threads are depicted in one of Screw threads are depicted in one of the following three ways: (1) The the following three ways: (1) The simplified version, which is most simplified version, which is most commonly used—especially in commonly used—especially in industries where manual drafting is still industries where manual drafting is still done, done,

Dimensioning SymbolsDimensioning Symbols

Simplified Form




Screw threads are depicted in one of Screw threads are depicted in one of the following three ways: (1) The the following three ways: (1) The simplified version, which is most simplified version, which is most commonly used—especially in commonly used—especially in industries where manual drafting is still industries where manual drafting is still done,done, (2) the schematic version which (2) the schematic version which is also popular, and used frequently in is also popular, and used frequently in industry, industry,


Simplified Form

Schematic Form




Screw threads are depicted in one of Screw threads are depicted in one of the following three ways: (1) The the following three ways: (1) The simplified version, which is most simplified version, which is most commonly used—especially in commonly used—especially in industries where manual drafting is still industries where manual drafting is still done, (2) the schematic version which done, (2) the schematic version which is also popular, and used frequently in is also popular, and used frequently in industry,industry, and and (3) the detailed method (3) the detailed method which is least often used because of the which is least often used because of the time to construct, and the fact that left- time to construct, and the fact that left- and right-hand threads are drawn in a and right-hand threads are drawn in a reversed angle format.reversed angle format.


Simplified Form

Schematic Form

Detailed Form



Dimensioning Screw ThreadsDimensioning Screw Threads

Screw threads are dimensioned Screw threads are dimensioned according to the standards ANSI Y14.6 according to the standards ANSI Y14.6 and ANSI Y14.6aM (Metric). For and ANSI Y14.6aM (Metric). For standard screw threads called out on standard screw threads called out on mechanical drawings, mechanical drawings, the major the major diameter is identified, followed by the diameter is identified, followed by the number of threads per inch and the number of threads per inch and the thread form, series, and class of fit.thread form, series, and class of fit. The The end of the screw threads is chamfered at end of the screw threads is chamfered at a 45º angle unless specified otherwise. a 45º angle unless specified otherwise. An external thread is designated by the An external thread is designated by the ‘A’ following the class of fit, whereas ‘A’ following the class of fit, whereas an internal thread is classified as a ‘B’ an internal thread is classified as a ‘B’ threadthread (A partial thread table is (A partial thread table is displayed on the next slide).displayed on the next slide).


.500 - 13UNC - 2A

Thread FormsAcmeUN - Unified NationalUNR – Unified National Round

Thread SeriesC – CoarseF – FineEF – Extra Fine


CoarseCoarseaa FineFineaa Extra FineExtra Finebb

Nominal Nominal NC and UNC NC and UNC NF and UNFNF and UNF NEF and UNEFNEF and UNEF Diameter Diameter Thds. per inch Thds. per inch Thds per inchThds per inch Thds per inchThds per inch

0 (.060)0 (.060) … … 80 80 … … 1 (.073)1 (.073) 64 64 72 72 … … 2 (.086)2 (.086) 56 56 64 64 … … 3 (.099)3 (.099) 48 48 56 56 … … 4 (.112)4 (.112) 40 40 48 48 … … 5 (.125)5 (.125) 40 40 44 44 … … 6 (.138)6 (.138) 32 32 40 40 … … 8 (.164)8 (.164) 32 32 36 36 … …

10 (.190)10 (.190) 24 24 32 32 … …12 (.216)12 (.216) 24 24 28 28 32 32

1/4 1/4 20 20 28 28 32 32 5/16 5/16 18 18 24 24 32 32 3/8 3/8 16 16 24 24 32 32 7/167/16 14 14 20 20 28 28 1/2 1/2 13 13 20 20 28 28 9/169/16 12 12 18 18 24 24

5/85/8 11 11 18 18 24 24 11/1611/16 … … … … 24 24 3/4 3/4 10 10 16 16 20 20 13/1613/16 … … … … 20 20 7/8 7/8 9 9 14 14 20 20 15/1615/16 … … … … 20 20 11 8 8 12 12 20 20

American National Standard, Unified, and American National American National Standard, Unified, and American National Screw Threads (Partial Table)Screw Threads (Partial Table)

aClasses 1A, 2A, 3A, 1B, 2B, 3B, 2, and 3 bClasses 2A, 2B, 2, and 3



Dimensioning Screw ThreadsDimensioning Screw Threads

2X R.02 MAX

.400 X .2


Perfect screw threads cannot be formed up snug against a perpendicular shoulder, such as the under side of a bolt head. If the bolt is intended to advance into the receiving tapped hole all the way to the head, the last two or three threads are often removed, or relieved, to avoid a conflict with imperfect threads.



Dimensioning Internal Screw ThreadsDimensioning Internal Screw Threads


An internal thread is usually called out in the circular view of the tapped holeAn internal thread is usually called out in the circular view of the tapped hole . . The minor diameter of the thread is represented by a solid object line, whereas the The minor diameter of the thread is represented by a solid object line, whereas the major diameter of the thread is represented by a hidden line. The dimension major diameter of the thread is represented by a hidden line. The dimension leader line is always radial and attaches to the solid line. leader line is always radial and attaches to the solid line.

.375 - 24UNF - 2B


4X .250 - 20UNC - 2B


Dimensioning internal screw threads requires that the major diameter of the threadDimensioning internal screw threads requires that the major diameter of the thread—in this specific case ¼ inch—be identified with a decimal dimension (.250), —in this specific case ¼ inch—be identified with a decimal dimension (.250), number of threads per inch (20), thread form and series (Unified National Coursenumber of threads per inch (20), thread form and series (Unified National Course—UNC), and the class of fit (2). The “B” specifies an —UNC), and the class of fit (2). The “B” specifies an internalinternal thread. thread.




Dimensioning Left-hand Screw ThreadsDimensioning Left-hand Screw Threads

Left-hand threads are called out by placing the letters LHLeft-hand threads are called out by placing the letters LH following the standard following the standard thread callout. Right-hand threads are assumed unless otherwise specified. thread callout. Right-hand threads are assumed unless otherwise specified.

.250 - 20UNC - 2A LH

Socket Head Cap Screw




Dimensioning Left-hand Screw ThreadsDimensioning Left-hand Screw Threads

This is an example of a left-hand thread callout for a This is an example of a left-hand thread callout for a tappedtapped hole. Remember, right-hand hole. Remember, right-hand threads are assumed unless otherwise specified. The feature is an internal, left-hand Unified threads are assumed unless otherwise specified. The feature is an internal, left-hand Unified screw thread, with a .250 major diameter, 20 threads per inch, and Unified National Course screw thread, with a .250 major diameter, 20 threads per inch, and Unified National Course series. The “2” represents the class of fit, and the “B” indicates that it is an internal thread.series. The “2” represents the class of fit, and the “B” indicates that it is an internal thread.

.250 - 20UNC - 2B LH




Dimensioning Dimensioning MetricMetric Screw Threads Screw Threads

This is an example of a metric thread callout for a This is an example of a metric thread callout for a tappedtapped hole. The tolerance grade (6H) is hole. The tolerance grade (6H) is assumed on metric specifications unless otherwise specified, so it could be removed without assumed on metric specifications unless otherwise specified, so it could be removed without consequence in this example.consequence in this example.

4X M10 X 1.5 – 6H

Metric thread formMajor diameter of thread (Basic)

Tolerance grade – internal thread

Pitch




Dimensioning Left-hand Dimensioning Left-hand MetricMetric Screw Threads Screw Threads

In this case, a metric thread with a nominal size of 8mm, and a pitch of 1.25, with In this case, a metric thread with a nominal size of 8mm, and a pitch of 1.25, with a tolerance grade of 6g (standard commercial grade) has been specified. The a tolerance grade of 6g (standard commercial grade) has been specified. The tolerance grade for standard fits are frequently omitted from the drawing, and are tolerance grade for standard fits are frequently omitted from the drawing, and are assumed unless otherwise specified.assumed unless otherwise specified.

M8 X 1.25 – 6g LH

Socket Head Cap Screw –(Left-hand Threads)

Metric thread formMajor diameter of thread

Tolerance grade – external threadPitch




Dimensioning Dimensioning MetricMetric Screw Threads Screw Threads

The cap screw depicted in this slide, has a metric thread exactly the same as the The cap screw depicted in this slide, has a metric thread exactly the same as the one shown in the previous slide. The tolerance grade has been omitted, but the one shown in the previous slide. The tolerance grade has been omitted, but the standard (6g) would be assumed in the absence of another specification.standard (6g) would be assumed in the absence of another specification.

M8 X 1.25




Constructing Hex Head Bolts and Hex NutsConstructing Hex Head Bolts and Hex Nuts

Regardless of the “true” projection of the hexagonal bolt head, or a nut fastener, Regardless of the “true” projection of the hexagonal bolt head, or a nut fastener, the three-segment representation is always usedthe three-segment representation is always used. In the example below, the . In the example below, the projection is true. However, in the next slide, the bolt will have been developed projection is true. However, in the next slide, the bolt will have been developed from a viewing station that has been revolved 90from a viewing station that has been revolved 90º from this one.º from this one.

.500 – 13 UNC – 2A




Constructing Hex Head Bolts and Hex NutsConstructing Hex Head Bolts and Hex Nuts

Even though the image is not a “true” projection, it is shown correctly according Even though the image is not a “true” projection, it is shown correctly according to projection conventions. Hexagon bolt heads and hex nuts are to projection conventions. Hexagon bolt heads and hex nuts are alwaysalways shown as shown as though oriented with three of the sides shown (otherwise, it would appear the though oriented with three of the sides shown (otherwise, it would appear the same as a bolt with a square head —as shown in the left view projection).same as a bolt with a square head —as shown in the left view projection).

.500 – 13 UNC – 2A

Correct ProjectionCorrect ProjectionIncorrect ProjectionIncorrect Projection




Projecting Hex Head Bolts, Hex Nuts and Jam NutsProjecting Hex Head Bolts, Hex Nuts and Jam Nuts

This slide depicts the construction and projection of bolts and nuts. The same This slide depicts the construction and projection of bolts and nuts. The same standard is followed in both the national and international standards.standard is followed in both the national and international standards.



Dimensioning KnurlingDimensioning Knurling

PITCH 0.8 RAISED DIAMOND KNURL

19.7 BEFORE KNURLING

28 FULL KNURL


Knurling on an external feature, such as shown here, requires the type of knurl Knurling on an external feature, such as shown here, requires the type of knurl (diamond, in this case), pitch, and diameter (diamond, in this case), pitch, and diameter beforebefore knurling. knurling.

M8 X 1.25



Dimensioning KnurlingDimensioning Knurling


Knurling of an external feature for an internal press fit requires the type of knurl (straight in this Knurling of an external feature for an internal press fit requires the type of knurl (straight in this case), pitch, and diameter case), pitch, and diameter beforebefore knurling. Where the diameter of the feature is to be controlled— knurling. Where the diameter of the feature is to be controlled—for instance to accommodate a press fit—the diameter for instance to accommodate a press fit—the diameter afterafter knurling must also be specified. knurling must also be specified.

PITCH 0.8 STRAIGHT KNURL 20 MIN AFTER KNURLING

19.7 BEFORE KNURLING

12.5 FULL KNURL

M8 X 1.25


End of Unit Number FourEnd of Unit Number Four

Thread Notation

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