Standard USA Bolt Shank Dimensions

1999-11-24, Rev. 1999-11-28.

All countries in the world except USA use millimeters (mm). USA citizens: To convert mm to inch, divide by 25.400.

Standard USA Bolt Shank Dimensions (All dimensions in units of mm unless otherwise specified.)

Unified Bolt ThreadsCoarse (UNC)

Unified Bolt ThreadsFine (UNF)

USA Size

Desig- nation

Nominal (Major) Diam-

eter,Dn

Threads per

inch,n

Pitch (mm per

thread), p

Tensile Stress Dia- meter,

Dt

Shear Stress Minor Dia- meter,

Ds

Threads per

inch,n

Pitch (mm per

thread),p

Tensile Stress Dia- meter,

Dt

Shear Stress Minor Dia- meter,

Ds

0 1.524 80 0.3175 1.215 1.112 1 1.854 64 0.3969 1.468 1.339 72 0.3528 1.510 1.396 2 2.184 56 0.4536 1.742 1.595 64 0.3969 1.798 1.669 3 2.515 48 0.5292 1.999 1.827 56 0.4536 2.073 1.925 4 2.845 40 0.6350 2.226 2.020 48 0.5292 2.329 2.157 6 3.505 32 0.7938 2.732 2.474 40 0.6350 2.887 2.680 8 4.166 32 0.7938 3.392 3.134 36 0.7056 3.478 3.249

10 4.826 24 1.0583 3.795 3.451 32 0.7938 4.053 3.795 12 5.486 24 1.0583 4.455 4.112 28 0.9071 4.603 4.308

0.2500 6.350 20 1.2700 5.113 4.700 28 0.9071 5.466 5.172 0.3125 7.938 18 1.4111 6.563 6.104 24 1.0583 6.906 6.563 0.3750 9.525 16 1.5875 7.978 7.463 24 1.0583 8.494 8.150 0.4375 11.112 14 1.8143 9.345 8.756 20 1.2700 9.875 9.463 0.5000 12.700 13 1.9538 10.796 10.162 20 1.2700 11.463 11.050 0.5625 14.288 12 2.1167 12.225 11.538 18 1.4111 12.913 12.454 0.6250 15.875 11 2.3091 13.625 12.875 18 1.4111 14.500 14.042 0.7500 19.050 10 2.5400 16.575 15.750 16 1.5875 17.503 16.988 0.8750 22.225 9 2.8222 19.475 18.559 14 1.8143 20.457 19.868 1.0000 25.400 8 3.1750 22.307 21.276 12 2.1167 23.338 22.650 1.1250 28.575 7 3.6286 25.040 23.861 12 2.1167 26.513 25.825

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Standard USA Bolt Shank Dimensions

1.2500 31.750 7 3.6286 28.215 27.036 12 2.1167 29.688 29.000 1.3750 34.925 6 4.2333 30.801 29.426 12 2.1167 32.863 32.175 1.5000 38.100 6 4.2333 33.976 32.601 12 2.1167 36.038 35.350

Pitch p is longitudinal length per thread. Note that p = 1 / n, where n = threads per unit length. For USA bolts, tensile stress diameter, by definition, is Dt = Dn –

0.974279 p.

For USA bolts, minor (shear) diameter, by definition, is Ds = Dn –

1.299038 p. For metric bolts, tensile stress diameter, by definition, is Dt = Dn –

0.938194 p. For metric bolts, minor (shear) diameter, by definition, is Ds = Dn –

1.226869 p.

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