steps for reading dimensions

8/3/2019 Steps for Reading Dimensions

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Steps FOR READING DIMENSIONS

1. 1

Many different sizes.

Read the numbers. They will look something like one of these:

o #4-40 x .5

o 1/4-20 x 5/8

o M3-50 x 10

2. 2

The major diameter for the threaded portion of the screw.

Interpret the first number. The first number gives the major, or largest, diameter.

o In Unified threads (measured in inches) there are numbered diameters #0 through #10, with 0

the smallest and 10 the largest. (Diameters #12 and #14 may also be found, but are usually on older

equipment and needed for repairs or restorations. #14 is close to, but not exactly the same as, 1/4-

inch.) The major diameter in Unified threads = 0.060" + 0.013"*(numbered diameter). So #2 has a

major diameter of 0.086". The odd numbers exist, but the even numbers are in far more common use.

o For screws larger than a #10, the diameters are listed in fractional inches. For instance, a 1/4-

20 screw has a 1/4-inch major diameter.
http://www.wikihow.com/Image:Screwthreaddia.jpghttp://www.wikihow.com/Image:Screwthreaddia.jpghttp://www.wikihow.com/Image:Screwthreadcallout1.jpghttp://www.wikihow.com/Image:Screwthreadcallout1.jpg


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o For metric threads, e.g. M3.5, the number following the M is the major diameter of the external

thread in millimeters.

3. 3

The distance between adjacent threads, or thread pitch.

Interpret the second number. It has to do with the distance between adjacent threads. It may be given as the

number of threads per unit length; or it may be given as the distance between threads, also called the thread

pitch.

o For Unified threads, the number given is threads per inch. For instance, a 1/4-20 screw has

20 threads per inch.

o For metric threads, the thread pitch is given in millimeters per thread. Thus, an M2 x 0.4 screw

has threads every 0.4mm. Although most metric fasteners have two or more standard pitches (fine &

coarse threads), the pitch is often omitted from a thread callout, it is always helpful to carry a sample

with you to the hardware store.

There are two major metric "industrial standards": DIN Deutsches Institut fr

Normung (German) and the JIS Japanese Industrial Standards. Although these standards are

closely related and often identical, there will be cases where say a JIS M8 bolt may not have

the same pitch as a DIN M8 bolt.

4. 4

The length of most screws is measured from the bottom of the head.
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Read the length, which is generally given after the "x". The length of most screws is measured from the

bottom of the head, as shown. Note, however, that a flathead screw, designed to sit flush in a countersunk

material, is measured to the top of the head.

o For unified threads the length is given in inches. A 1/4-20 x 3/4 screw is .75 inches long. The

length may be given in fractional inches or the decimal equivalent.

o For metric threads, the length is given in millimeters.

5. 5

Understand some other nomenclature that sometimes goes with screw threads.

o

Nuts have internal threads.

Thread classes refer to fit, how loosely or tightly the screw fits in the nut. The most common thread

classes are 2A or 2B. A indicates an external thread, such as on a screw or bolt. B indicates aninternal thread, such as on a nut. The 2 (or, far less commonly, 1 or 3) describes the tightness of the

fit.

o You may see the abbreviations UNC and UNF. These stand for unified coarse and unified

fine, respectively, and they refer to standard series of thread pitch. Each series assigns a pitch to

diameter. For instance, a #10 UNC screw has 24 threads per inch, whereas a #10 UNF screw has 32

threads per inch. If a thread is specified by its series, look for the pitch in a table.

o Minor diameter is the smallest diameter of the thread, the innermost diameter. Major diameter

is the largest diameter of the thread, the outermost diameter. The diameter given is typically the

nominal major diameter of an external, or male, thread.

6. 6
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American/United National Threads

Size DiameterTPI

Coarse

TPI

Fine

Root Dia.

Coarse

Hex

Head

Size

SAE

Washer

ID

SAE

Washer

OD

SAE

Washer

Thickness

#0 0.0600 - 80 0.0447

#1 0.0730 64 72 0.0560

#2 0.0860 56 64 0.0668 3/32"1/4"

1/32"

#3 0.0990 48 56 0.0771

#4 0.1120 40 48 0.0813 1/8"5/16"

1/32"

#5 0.1250 40 44 0.0971

#6 0.1380 32 40 0.1073 5/32"3/8"

3/64"

#8 0.1640 32 36 0.1299 3/16"7/16"

3/64"

#10 0.1900 24 32 0.1570 7/32"1/2"

1/16"

#12 0.2160 24 28 0.1722 1/4"9/16"

1/16"1/4" 0.2500 20 28 0.1850

3/8"9/32"

5/8"1/16"

5/16" 0.3125 18 24 0.24001/2"

11/32"11/16"

1/16"

3/8" 0.3750 16 24 0.2940 9/16" 13/32" 13/16" 1/16"7/16" 0.4375 14 20 0.3440

5/8"15/32"

15/16"1/16"

1/2" 0.5000 13 20 0.40003/4"

17/32" 1-1/16"

3/32"9/16" 0.5625 12 18 0.4540

7/8"19/32" 1-

3/16"3/32"

5/8" 0.6250 11 18 0.507015/16"

21/32" 1-5/16"

3/32"3/4" 0.7500 10 16 0.6200 1-

1/8"13/16" 1-

1/2"1/8"


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7/8" 0.8750 9 14 0.7310 1-5/16"

15/16" 1-3/4"

1/8"

1" 1.0000 8 12 0.8370 1-1/2" 1-1/16" 1-

3/4"1/8"

Metric Threads

Metric threads use the same thread profile as SAE threads. The biggest difference is that the

thread pitch (distance between consecutive threads) is given instead of threads per unit distance.

Diameter

Coarse

Pitch

mm

Fine

Pitch

mm

Root Dia.

Coarse

mm

Hex

Head

Size

mm

ISO

Washer

ID

mm

ISO

Washer

OD

mm

ISO

Washer

Thickness

mm

1 0.25 0.7294

1.1 0.25 0.8294

1.2 0.25 0.9294

1.4 0.30 1.075

1.6 0.35 1.221 3.2

1.8 0.35 1.421

2 0.40 1.567 4

2.2 0.45 1.713

2.5 0.45 2.013 5

3 0.50 2.459 5.5 3.4 7.0 0.6

3.5 0.60 2.850


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4 0.70 0.50 3.242 7 4.5 9.0 0.9

4.5 0.75 0.50 3.688

5 0.80 0.50 4.134 8 5.5 10 11

5.5 0.50

6 1.00 0.50 4.917 10 6.7 12.5 1.8

7 1.00 0.75 5.917

8 1.25 0.75 6.647 13 8.7 17 1.8

9 1.25 0.75 7.647

10 1.50 0.75 8.376 16 10.9 21 2.2

11 1.50 0.75 9.376

12 1.75 0.75 10.11 18 13.4 24 2.7

14 2.00 1.00 11.83 21

16 2.00 1.00 13.83 24 17.4 30 3.318 2.50 1.00 15.29

20 2.50 1.00 17.29 30 21.5 37.9 3.3

Bolt Strength

Bolt Strength

The Society of Automotive Engineering has issued standard J429, which sets forth standards forboth strength. The SAE grade of a bolt is marked on it's head in the form of short radial lines, the

number of lines being two less than the SAE grade (i.e.. 3 lines for grade 5).

SAE Grade Size Range Strength (psi)

1 1/4" to 1-1/2" 60,000

2 1/4" to3/4" 74,000

2 7/8" to 1-1/2" 60,000

5 1/4" to 1" 120,000

5 1-1/8" to 1-1/2" 105,000

7 1/4" to 1-1/2" 133,000

8 1/4" to 1-1/2" 150,000

ASTM standards are sometimes used as well; A325 bolts are the equivalent of SAE 5, and A490

bolts are the equivalent of SAE 8.

Preload

A very misunderstood part of bolting stuff together ispreload, which is the tension placed on the

bolt by the nut (as opposed to the load). A sufficiently high preload will protect the bolt from


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fatigue as the load changes, as the varying load will change the clamping force on the bolted

components, rather than the tension on the bolt. (This is not strictly true, but for a tinkerer like

me, it's adequate.) As a rule of thumb, the preload should exceed the maximum load by 15% orso.

In order for this to work, however, the joint must be stiffer than the bolt. For this reason, theshank of high-tech bolts are often necked down to the same diameter of the root of the thread. As

long as it isn't thinner than the root of the thread, it isn't any weaker than the thread, and thereforedoesn't effect overall bolt strength, but it is significantly less stiff than the original shank.

There are two ways to measure preload on a bolt; a torque wrench, and by measuring the angle

the nut has turned. Of the two, the latter is more accurate, as friction plays a significant - and

more importantly, indeterminate - role when using a torque wrench.

Torque = K preload diameter

K, the so-calledNut Factor, usually varies between 0.3 and 0.1, and is very sensitive to a numberof factors, ranging from temperature to thread condition, even to how fast the bolt is tightened.

Measuring the angle the nut has turned is simply measuring how much the bolt is stretching,

equal to the pitch (distance between threads) times the number of turns. Using this requires thatthe components being bolted don't compress much (or compress a known amount), and that the

"spring rate" of the bolt be known.

Turns = preload (spring rate pitch)

For example, if the "spring rate" of a 1/2-13 bolt is 50,000 pounds per inch (note that I made that

up, and that most bolts will yield longbefore stretching an inch), and you need 500 pounds ofpreload, you'll need to stretch the bolt 500 50000 = 0.01 inch. At 13 threads per inch (0.0769

inches per thread), this would equate to 0.13 turns, or about 45 past snug.

If more than one bolt is used in a joint, and those bolts are closer together than about fourdiameters, the preload on one bolt will effect the preload on the other bolts by compressing the

joint. This effect is called "crosstalk", and then all bets are off. Joints that are significantly less

stiff than the bolts, such as joints involving gaskets, suffer much worse from crosstalk. The bestway to control crosstalk is to use a carefully thought out tightening sequence (usually a spiral

starting at the center, or for circular patterns, alternating bolts), and to tighten the bolts in small

steps. Even so, it's a crap shoot.


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Table of Bolt Sizes ...ISO metric precision hexagon bolts , Coarse Thread Series,Bolt tolerance class 6g

Thread Form to BS 3643

Nominal (D) Thread. Bolt dia Bolt Head Bolt Nut

Size PitchMajor(d)

max - minMinor(d3 )max - min

PitchDiameter (d2

)max - min

Thick (Zb)Acc/Flats

(A/F)max - min

Acc./Corn(A/C)

M3 0,5 2,980 - 2,874 2,439 -2,272 2,655 - 2,580 2,125 5,50 - 5,38 6,40

M4 0,7 3,978 - 3,838 3,220 - 3,002 3,523 - 3,433 2,925 7,00 - 6,85 8,10

M5 0,8 4,976 - 4,826 3,869 - 4,110 4,456 - 4,361 3,650 8,00 - 7,85 9,20

M6 1,0 5,974 - 5,794 4,891 - 4,596 5,324 - 5,212 4,150 10,00 - 9,78 11,50

M8 1,25 7,972 - 7,760 6,272 - 6,619 7,160 - 7,042 5,650 13,00 - 12,73 15,00

M10 1,5 9,968 - 9,732 8,344 - 7,938 8,994 - 8,862 7,180 17,00 - 16,73 19,60

M12 1,7511,966 -11,701

10,072 -9,601

10,829 -10,679

8,180 19,00 - 18,67 22,10

M16 2,0 15,962 -15,682 13,797 -13,271 14,663 -14,503 10,180 24,00 - 23,67 27,70

M20 2,519,958 -19,623

17,252 -16,624

18,334 -18,164

13,215 30,00 - 29,67 34,60

M24 3,023,952 -23,577

20,701 -19,955

22,003 -21,803

15,215 36,00 - 35,58 41,60

M30 3,5029,947 -29,522

26,158 -25,306

27,674 -27,462

19,260 46,00 - 45,38 53,1

M36 4,0035,940 -35,465

31,610 -30,654

33,342 -33,118

23,260 55,00 - 54,26 63,5


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Nuts Sizes, Coarse Thread Series

Nut tolerance class 6H are dimensioned in BS3692

Thread form to BS 3643

Nominal Thread. Nut Diameter Nut

Size Pitch Major (D)Minor (D1 )Max - min

Thick (Zn)

M3 0,5 3,000 2,599 - 2,459 2,40

M4 0,7 4,000 3,422 - 3,242 3,20

M5 0,8 5,000 4,334 - 4,134 4,00

M6 1,0 6,000 5,153 - 4,917 5,00

M8 1,25 8,000 6,912 - 6,647 6,50

M10 1,5 10,000 8,676 - 8,376 8,00

M12 1,75 12,00010,441 -10,106

10,00

M16 2,0 16,00014,210 -13,835

13,00

M20 2,5 20,00017,744 -17,294

16,00


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M24 3,0 24,00021,252 -20,752

19,00

M30 3,5 30,00026,771 -26,211

24,00

M36 4,0 36,0032,270 -31,670

29,00

Bolt Sizes ...ISO metric precision hexagon bolts , Fine thread series

Bolt tolerance class 6g are dimensioned in BS3692:1967

Nominal Thread. Bolt dia (d) Bolt Head Bolt Nut

Size PitchMajor

max - minMinor

max - min

PitchDiametermax - min

Thick (Zb)Acc/Flatsmax - min

(A/F)

Acc./Corn(A/C)

M6 0,75 5,978 - 5,838 5,166 - 4,929 5,491 - 5,391 4,150 10,00 - 9,78 11,50

M8 1,00 7,974 - 7,794 6,891 - 6,596 7,324 - 7,212 5,650 13,00 - 12,73 15,00

M10 1,25 9,972 - 9,760 8,619 - 8,272 9,160 - 9,042 7,180 17,00 - 16,73 19,60

M12 1,2511,972 -11,760

10,619 -10,258

11,160 -11,028

8,180 19,00 - 18,67 22,10

M16 1,5015,968 -15,732

14,344 -13,930

14,994 -14,854

10,180 24,00 - 23,67 27,70

M20 1,519,968 -19,732

18,344 -17,930

18,994 -18,854

13,215 30,00 - 29,67 34,60

M24 2,023,962 -23,682

21,797 -21,261

22,663 -22,493

15,215 36,00 - 35,58 41,60

M30 2,029,962 -29,682

27,797 -27,261

28,663 -28,493

19,260 46,00 - 45,38 53,1

M36 3,0035,952 -35,577

32,704 -31,955

34,003 -33,803

23,260 55,00 - 54,26 63,5

Nuts Sizes - Fine Thread Series..

Nut tolerance class 6H are dimensioned in BS3692:1967


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Nominal Thread. Nut Diameter Nut

Size Pitch MajorMinor

Max - minThick (Zn)

M6 0,75 6,000 5,378 - 5,188 5,00

M8 1,00 8,000 7,153 - 6,917 6,50

M10 1,25 10,000 8,912 - 8,647 8,00

M12 1,25 12,000

10,912 -

10,647 10,00

M16 1,50 16,00014,676 -14,376

13,00

M20 1,50 20,00018,676 -18,376

16,00

M24 2,0 24,00022,210 -21,835

19,00

M30 2,0 30,00028,210 -27,835

24,00

M36 3,0 36,0033,252 -32,752

29,00

Washers.. Plain Washers , bright metric series

Bright Washers are dimensioned in BS4320: 1968

Nominal Washer Diameter Washer Thickness

SizeInternal

max - minExternal

max - minThick

max - minThin

M3 3,4 - 3,2 7,0 - 6,7 0,6 - 0,4 -

M4 4,5 - 4,3 9,0 - 8,7 0,9 - 0,7 -

M5 5,5 - 5,3 10,0 - 9,7 1,1 - 0,9 -

M6 6,7 - 6,4 12,5 - 12,1 1,8 - 1,4 0,9 - 0,7

M8 8,7 - 8,4 17,0 - 16,6 1,8 - 1,4 1,1 - 0,9

M10 10,9 - 10,5 21,0 - 20,5 2,2 - 1,8 1,45 - 1,05

M12 13,4 - 13,0 24,0 - 23,5 2,7 - 2,3 1,8 - 1,4

M16 17,4 - 17,00 30,0 - 29,5 3,3 - 2,7 2,2 - 1,8

M20 21,5 - 21,0 37,0 - 36,2 3,3 - 2,7 2,2 - 1,8

M24 25,5 - 25,0 44,0 - 43,2 4,3 - 3,7 2,7 - 2,3

M30 31,6 - 31,0 56,0 - 55,0 4,3 - 3,7 2,7 - 2,3

M36 37,6 - 37,0 66,0 - 65,0 5,6 - 4,4 3,3 - 2,7


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Washers.. Plain Washers , Black metric series

Black Washers are dimensioned in BS4320: 1968

Nominal Washer DiameterWasher

Thickness

SizeInternal

max - minExternal

max - minThicknessmax - min

M5 5,8 - 5,5 10,0 - 9,2 1,2 - 0,8

M6 7,0 - 6,6 12,5 - 11,7 1,9 - 1,3

M8 9,4 - 9,0 17,0 - 16,2 1,9 - 1,3

M10 11,5 - 11,0 21,0 - 20,2 2,3 - 1,7

M12 14,5 - 14,0 24,0 - 23,2 2,8 - 2,2

M16 18,5 - 18,00 30,0 - 29,2 3,6 - 2,4

M20 22,6 - 22,0 37,0 - 35,8 3,6 - 2,4

M24 26,6 - 26,0 44,0 - 42,8 4,6 - 3,4

M30 33,8 - 33,0 56,0 - 54,5 4,6 - 3,4

M36 39,8 - 39,0 66,0 - 64,5 6,0 - 4,0

M42 45,8 - 45,0 78,0 - 76,5 8,2 - 5,8

M48 53,0 - 52,0 92,0 -90,0 9,2 - 6,8

Grade and Strength Information

There are numerous standards that fasteners are manufactured to, and those standards describe

everything from material chemistry to surface finish to heat treatment. The most relevant numbers are

"Proof Stress," "Yield Stress" and "Tensile / Ultimate Stress." Tensile Strength is how much stress the

material can withstand before finally ripping apart. Yield Stress is the amount of stress that a material can

undergo before permanently stretching. Proof stress is similar to Yield stress except that it is slightly less

(about 90%), and only applies to fasteners. The thread geometry causes them to yield slightly before the

Yield stress level of the material, so Proof Stress can be thought of the true yield--in other words, the

fastener will behave like a spring below that stress level.


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So which of these numbers should be used? While there are many arguments for tightening a screw

past its yield point (for instance), from this author's viewpoint, if an external load yields a screw, and if that

load is ever removed, the screw will now be permanently stretched and loose. Therefore, we recommend

designing so that the combined internal and external loads stay below the proof stress to avoid

any possibility of yielding. If proof stress is unknown, 85% of Yield stress can be used as an

approximation. The ultimate or tensile stress is sometimes designed to, but we do not know when this

acceptable or not. Also, the ultimate stress is used in designing joints for alternating loads, but this isbeyond our scope.

Several organizations publish standards for fasteners. For inch/english, this includes SAE, ASTM, ANSI,

ASME and others, although the most commonly used are the SAE "Grades." (standard J429). The most

common metric specifications are published by the ISO. (ANSI metric specs agree with ISO for all

practical purposes--Machinery's Handbook)

Common Inch / Imperial SAE Grades: (all values in ksi or 1000 lbs /

square inch)

HeadMarking

Grade Diameter (in) Proof Strength Yield Strength Tensile (Ultimate)

Strength

2 1/4 to 3/4 55 57 74

3/4 to 1-1/2 33 36 60

5 1/4 to 1 85 92 120

1 to 1-1/2 74 81 105

8 1/4 to 1-1/2 120 130 150

Socket Head Cap Screws made from alloy steel are typically manufactured to a higher strength than SAE

Grade 8: 180 ksi tensile strength for fasteners up to 1/2 inch, 170 ksi for larger sizes (ASTM A574, p. G-

34).

For many more head markings and their corresponding specifications, see here.

Metric ISO Marking

Metric fasteners are marked with two numbers separated by a decimal point, like 10.9. The 10 is 1/100 of

tensile strength in MPa, and the .9 represents the ratio of yield to tensile strength. So 10.9 represents a

tensile strength of 1000 MPa and yield of 900 MPa. Some strengths are stronger than this method shows,

see table 10 on this page. Other references for this table: hereandhere.

Grade size range proof

strength (MPa)

approx yield

strength (MPa)

tensile

strength (MPa)

approx equiv.

to SAE grade:
http://www.appliedbolting.com/pdf/yielding.pdfhttp://www.appliedbolting.com/pdf/yielding.pdfhttp://www.americanfastener.com/technical/grade_markings_steel.asphttp://www.americanfastener.com/technical/grade_markings_steel.asphttp://euler9.tripod.com/bolt-database/22.htmlhttp://www.utm.edu/departments/engin/lemaster/Machine%20Design/Lecture%2028.pdfhttp://www.utm.edu/departments/engin/lemaster/Machine%20Design/Lecture%2028.pdfhttp://www.boltdepot.com/fastener-information/Materials-and-Grades/Bolt-Grade-Chart.aspxhttp://www.boltdepot.com/fastener-information/Materials-and-Grades/Bolt-Grade-Chart.aspxhttp://www.boltdepot.com/fastener-information/Materials-and-Grades/Bolt-Grade-Chart.aspxhttp://www.appliedbolting.com/pdf/yielding.pdfhttp://www.americanfastener.com/technical/grade_markings_steel.asphttp://euler9.tripod.com/bolt-database/22.htmlhttp://www.utm.edu/departments/engin/lemaster/Machine%20Design/Lecture%2028.pdfhttp://www.boltdepot.com/fastener-information/Materials-and-Grades/Bolt-Grade-Chart.aspx


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grade dec x tensile*

4.8 M1.6-M16 310 336 420 SAE 2

8.8 < M16 580 640 800 SAE 5

M16-M76 600 660 830

10.9 > M5 830 940 1040 SAE 8

12.9 M1.6-M100 970 1100 1220 ASTM-A574

alloy socket

screws

*these value aren't necessarily from the standards, they're calculated as described above.

Tensile stress areas and acceptable load estimates for various grades

For applications where there is any chance of bodily or property harm, don't rely on our external load

estimates--they are intended to give a rough approximation of what screws of various grades can

hold in non-critical applications, and are based on the following assumptions:

We use the proof strength as the maximum stress that should be endured from the combined

internal (original tightening) and external loads.

If proof load isn't specified in the above tables, we use 85% of yield

It is assumed that the joint is twice as stiff as the bolt, which implies that 1/3 of the external load is

seen by the bolt, and the other 2/3 goes into reducing clamping load. The forumla explained above

and used below is 60% * proof * tensile area / 1.0 (safety factor). We recommend using a 2.5safety factor for non-critical / costly applications--ie, divide the numbers below by 2.5.For joints

clamping aluminum, plastic, gaskets or other softer material it's safer to assume that 100% of external

load is seen by the fastener (multiply by 20% instead of 60%).

tensile stress area:Tests have shown that the average of the minor and pitch diameters

approximates the effective area of a fastener. The Machinery's handbook has a different formula for

bolts with tensile strengths over 100ksi, but due to some doubtabout its origins, we don't use it.

As far as we can tell, SAE Grades apply only to bolts at least 1/4" in diameter. Any unmarked

machine screws smaller than that are probably Grade 2; we show the higher Grades for reference

only on those sizes. Alloy steel socket head cap screws will most likely have a greater strength than

SAE Grade 8 unless their manufacturer says otherwise.

We assume shear loads and torsional loads from tightening are zero.

For alloy socket screws, yield strength is 180 ksi until 1/2" and 170 ksi for larger diameters. Weuse 85% of these values to approximate proof strength.

Inch tensile areas and loads (in lbs), both fine and coarse thread

size - dec. major tensile Grade 2 Grade 5 Grade 8 alloy socket
http://www.eng-tips.com/viewthread.cfm?qid=33175&page=2http://www.eng-tips.com/viewthread.cfm?qid=33175&page=2http://www.eng-tips.com/viewthread.cfm?qid=33175&page=2


15/20

threads / in diameter (in) stress area

square inches

(proof strength:


16/20

3/4-10 .75 .334 6613.2 17034 24048 28957.8

3/4-16 .75 .373 7385.4 19023 26856 32339.1

7/8-9 .875 .462 9147.6 23562 33264 40055.4

7/8-14 .875 .509 10078.2 25959 36648 44130.3

1-8 1.0 .606 11998.8 30906 43632 52540.2

1-12 1.0 .663 13127.4 33813 47736 57482.1

alternative load carrying recommendations: here.

Standard Thread Pitches

Coarse Thread Series (UNC/UNRC) is the most common designation for general application bolts and nuts. Coarse

thread is beneficial, because they are less likely to cross thread, more tolerant in adverse conditions and facilitate

quick assembly.

Fine Thread Series (UNF/UNRF) is commonly used in precision applications. Because of the larger tensile stress

areas, they have high tension strength. However, a longer engagement is required for fine thread applications than

for coarse series threads to prevent stripping.

8 - Thread Series (8UN) is the specified thread forming method for several ASTM standards including A193 B7,

A193 B8/B8M, and A320. This series is used for diameters one inch and above.
http://www.pencomsf.com/pdf/tech_info.pdfhttp://www.pencomsf.com/pdf/tech_info.pdf


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Coarse Thread Series -

UNCFine Thread Series - UNF 8-Thread Series - 8UN

Nomi

nal

Sizeand

Threa

ds

Per

In.

Basic

PitchDia.

Sectio

n at

Minor

Dia.

Tensil

e

Stress

Area

Nomin

al Sizeand

Threa

ds Per

In.

Basic

PitchDia.

Sectio

n at

Minor

Dia.

Tensil

e

Stress

Area

Nomin

al Sizeand

Threa

ds Per

In.

Basic

PitchDia.

Secti

on at

Minor

Dia.

Tensi

le

Stress

Area

In. Sq in. Sq in. In. Sq in. Sq in. In. Sq in. Sq in.

-- -- -- -- -- 0 - 800.051

9

0.0015

1

0.0018

0

-- -- -- -- --

1 - 640.062

9

0.0021

8

0.0026

31 - 72

0.064

0

0.0023

7

0.0027

8

2 - 560.074

4

0.0031

0

0.0037

02 - 64

0.075

9

0.0033

9

0.0039

4

3 - 480.085

5

0.0040

6

0.0048

73 - 56

0.087

4

0.0045

1

0.0052

3

4 - 400.095

8

0.0049

6

0.0060

44 - 48

0.098

5

0.0056

6

0.0066

1

-- -- -- -- --

5 - 40 0.1088

0.00672

0.00796

5 - 44 0.1102

0.00716

0.00830

6 - 320.117

7

0.0074

5

0.0090

96 - 40

0.121

8

0.0087

4

0.0101

5

8 - 320.143

7

0.0119

60.0140 8 - 36

0.146

0

0.0128

5

0.0147

4

10 -

24

0.162

9

0.0145

00.0175 10 - 32

0.169

70.0175 0.0200 -- -- -- -- --

12 -

24

0.188

90.02060.0242 12 - 28

0.192

80.0226 0.0258 -- -- -- -- --

14 - 200.217

50.0269 0.0318 14 - 28

0.226

80.0326 0.0364 -- -- -- -- --

516 - 0.276 0.04540.0524516 - 24 0.285 0.0524 0.0580 -- -- -- -- --


18/20



Nomi

nal

Sizeand

Threa

ds

Per

Basic

PitchDia.

Sectio

n at

Minor

Dia.

Tensil

e

Stress

Area

Nomin

al Size

and

Threa

ds Per

In.

Basic

PitchDia.

Sectio

n at

Minor

Dia.

Tensil

e

Stress

Area

Nomin

al Size

and

Threa

ds Per

In.

Basic

PitchDia.

Secti

on at

Minor

Dia.

Tensi

le

Stress

Area


18 4 4

38 - 160.334

40.0678 0.0775 38 - 24

0.347

90.0809 0.0878 -- -- -- -- --

7

16 -14 0.3911 0.0933 0.1063716 - 20 0.4050 0.1090 0.1187 -- -- -- -- --

12 - 130.450

00.1257 0.1419 12 - 20

0.467

50.1486 0.1599 -- -- -- -- --

916 -

12

0.508

40.162 0.182 916 - 18

0.526

40.189 0.203 -- -- -- -- --

58 - 110.566

00.202 0.226 58 - 18

0.588

90.240 0.256 -- -- -- -- --

34 - 100.685

00.302 0.334 34 - 16

0.709

40.351 0.373 -- -- -- -- --

78 - 90.802

80.419 0.462 78 - 14

0.828

60.480 0.509 -- -- -- -- --

1 - 80.918

80.551 0.606 1 - 12

0.945

90.625 0.663 1 - 8

0.918

80.551 0.606

118 - 71.032

20.693 0.763

118 -

12

1.070

90.812 0.856 118 - 8

1.043

80.728 0.790

114 - 71.157

20.890 0.969

114 -

12

1.195

91.024 1.073 114 - 8

1.168

80.929 1.000

138 - 61.266

71.054 1.155

138 -

12

1.320

91.260 1.315 138 - 8

1.293

81.155 1.233

112 - 6 1.391 1.294 1.405 112 - 1.445 1.521 1.581 1

12 - 8 1.418 1.405 1.492


19/20



Nomi

nal

Sizeand

Threa

ds

Per

Basic

PitchDia.

Sectio

n at

Minor

Dia.

Tensil

e

Stress

Area

Nomin

al Size

and

Threa

ds Per

In.

Basic

PitchDia.

Sectio

n at

Minor

Dia.

Tensil

e

Stress

Area

Nomin

al Size

and

Threa

ds Per

In.

Basic

PitchDia.

Secti

on at

Minor

Dia.

Tensi

le

Stress

Area


7 12 9 8

-- -- -- -- -- -- -- -- -- -- 158 - 81.543

81.68 1.78

134 - 5 1.6201 1.74 1.90 -- -- -- -- -- 134 - 8 1.6688 1.98 2.08

-- -- -- -- -- -- -- -- -- -- 178 - 81.793

82.30 2.41

2 - 4121.855

72.30 2.50 -- -- -- -- -- 2 - 8

1.918

82.65 2.77

214 -

4-12

2.105

73.02 3.25 -- -- -- -- -- 214 - 8

2.168

83.42 3.56

212 - 42.337

63.72 4.00 -- -- -- -- -- 212 - 8

2.418

84.29 4.44

234 - 42.587

64.62 4.93 -- -- -- -- -- 234 - 8

2.668

85.26 5.43

3 - 42.837

65.62 5.97 -- -- -- -- -- 3 - 8

2.918

86.32 6.51

314 - 43.087

66.72 7.10 -- -- -- -- -- 314 - 8

3.168

87.49 7.69

312 - 43.337

67.92 8.33 -- -- -- -- -- 312 - 8

3.418

88.75 8.96

334 - 43.587

69.21 9.66 -- -- -- -- -- 334 - 8

3.668

810.11 10.34

4 - 4 3.837 10.61 11.08 -- -- -- -- -- 4 - 8 3.918 11.57 11.81


20/20



Nomi

nal

Sizeand

Threa

ds

Per

Basic

PitchDia.

Sectio

n at

Minor

Dia.

Tensil

e

Stress

Area

Nomin

al Size

and

Threa

ds Per

In.

Basic

PitchDia.

Sectio

n at

Minor

Dia.

Tensil

e

Stress

Area

Nomin

al Size

and

Threa

ds Per

In.

Basic

PitchDia.

Secti

on at

Minor

Dia.

Tensi

le

Stress

Area


6 8

steps for reading dimensions

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