CAP SCREWS & BOLTS

Head & Thread

HEX CAP SCREWS Dimensions

†Length of a cap screw is measured from the underhead bearing surface to the extreme end of the screw.

Hex Cap Screws ASME B18.2.1-2012

E F G H J LT Y
Thread Length
Nominal or Transition
Body Width Across Wrenching
Basic Product Width Across Flats Head Height For Screw For Screw Thread
Diameter Diameter Corners Height Lengths Lengths Length
≤ 6 in. > 6 in.

Max Min Basic Max Min Max Min Basic Max Min Min Ref Ref Max
1/4 0.2500 0.2500 0.2450 7/16 0.438 0.428 0.505 0.488 5/32 0.163 0.150 0.106 0.750 1.000 0.250

5/16 0.3125 0.3125 0.3065 1/2 0.500 0.489 0.577 0.557 13/64 0.211 0.195 0.140 0.875 1.125 0.278

3/8 0.3750 0.3750 0.3690 9/16 0.562 0.551 0.650 0.628 15/64 0.243 0.226 0.160 1.000 1.250 0.312

7/16 0.4375 0.4375 0.4305 5/8 0.625 0.612 0.722 0.698 9/32 0.291 0.272 0.195 1.125 1.375 0.357

1/2 0.5000 0.5000 0.4930 3/4 0.750 0.736 0.866 0.840 5/16 0.323 0.302 0.215 1.250 1.500 0.385

9/16 0.5625 0.5625 0.5545 13/16 0.812 0.798 0.938 0.910 23/64 0.371 0.348 0.250 1.375 1.625 0.417

5/8 0.6250 0.6250 0.6170 15/16 0.938 0.922 1.083 1.051 25/64 0.403 0.378 0.269 1.500 1.750 0.455

3/4 0.7500 0.7500 0.7410 1-1/8 1.125 1.100 1.299 1.254 15/32 0.483 0.455 0.324 1.750 2.000 0.500

7/8 0.8750 0.8750 0.8660 1-5/16 1.312 1.285 1.516 1.465 35/64 0.563 0.531 0.378 2.000 2.250 0.556

1 1.0000 1.0000 0.9900 1-1/2 1.500 1.469 1.732 1.675 39/64 0.627 0.591 0.416 2.250 2.500 0.625

1-1/8 1.1250 1.1250 1.1140 1-11/16 1.688 1.631 1.949 1.859 11/16 0.718 0.658 0.461 2.500 2.750 0.714

1-1/4 1.2500 1.2500 1.2390 1-7/8 1.875 1.812 2.165 2.066 25/32 0.813 0.749 0.530 2.750 3.000 0.714

1-1/2 1.5000 1.5000 1.4880 2-1/4 2.250 2.175 2.598 2.480 15/16 0.974 0.902 0.640 3.250 3.500 0.833

Nominal Screw Length

Nominal Screw
Size Over 1 in. to Over 2-1/2 in. to Over 4 in. to
Up to 1 in., incl. Longer than 6 in.
2-1/2 in., incl. 4 in., incl. 6 in., incl.
1/4 to 3/8 -0.03 -0.04 -0.06 -0.10 -0.18
Tolerance on Length
7/16 and 1/2 -0.03 -0.06 -0.08 -0.10 -0.18

9/16 to 3/4 -0.03 -0.08 -0.10 -0.10 -0.18

7/8 and 1 .... -0.10 -0.14 -0.16 -0.20

1-1/8 to 1-1/2 .... -0.12 -0.16 -0.18 -0.22

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 CAP SCREWS & BOLTS

Gr.2, 18-8 & 316 SS HEX CAP SCREWS

x
GRADE-2 HEX CAP SCREW
A low or medium carbon steel, externally threaded mechanical device 1/4” diameter or larger, with a trimmed hex head and a
Description washer face on the bearing surface.

Applications/ Economical for use in non-critical applications where the fastener is not subject to extreme temperatures or stress beyond the
Advantages limits listed herein.

Material AISI 1006 - 1050 or equivalent steel.

1/4 through 3/4 in. diameter, 6 in. and shorter in length: Rockwell B80 - B100.
Hardness 1/4 through 3/4 in. diameter, over 6 in. in length: Rockwell B70 - B100.
7/8 through 1-1/2 in. diameter, all lengths: Rockwell B70 - B100.
1/4 through 3/4 in. diameter, 6 in. and shorter in length: 55,000 psi.
Proof Load 1/4 through 3/4 in. diameter, over 6 in. in length: 33,000 psi.
7/8 through 1-1/2 in. diameter, all lengths: 33,000 psi.
1/4 through 3/4 in. diameter, 6 in. and shorter in length: 57,000 psi. minimum.
Yield Strength* 1/4 through 3/4 in. diameter, over 6 in. in length: 36,000 psi. minimum.
7/8 through 1-1/2 in. diameter, all lengths: 36,000 psi. minimum.
1/4 through 3/4 in. diameter, 6 in. and shorter in length: 74,000 psi. minimum.
Tensile Strength 1/4 through 3/4 in. diameter, over 6 in. in length: 60,000 p si. minimum.
7/8 through 1-1/2 in. diameter, all lengths: 60,000 psi. minimum.

Elongation* 18% minimum (all diameters)

Reduction of Area* 35% minimum (all sizes)

Plating See Appendix-A for plating information

x
HEX CAP SCREW--STAINLESS STEEL, 18-8 & 316 x

Description 18-8 and 316 stainless steel cap screws are both made from austenitic alloys as described below.

18-8: Used in products that require general atmospheric corrosion resistance, such as chemical and food-processing equipment.
Applications/ Some chemical environments may require special corrosion resistant materials and precautions.
Advantages 316: The molybdenum content gives this type of stainless even greater corrosion resistance than 18-8 as well as superior strength
at high temperatures.
18-8: A cap screw made from one of the following austenitic alloys: 303, 303Se, 304, XM7, all of which are characterized as
having a chromium content of 17-19% and nickel content of 8-10%.
Material 316: A cap screw made from 316 stainless steel, an austenitic alloy which differs from 18-8 by its molybdenum content (2-3%)
and a higher nickel content (10-14%).
The austenitic alloys develop their strength through work hardening during the fastener manufacturing process, as seen from the
Heat Treatment hardness properties below. The only heat treatment normally available on austenitic stainless alloys is annealing, which is done at
approximately 1900°F to a dead soft condition and is not normally thermally reversible.
1/4 through 5/8 in. diameter: Rockwell B95 - C32
Hardness 3/4 through 1 in. diameter: Rockwell B80 - C32
1/4 through 5/8 in. diameter, 2.25D and longer: 65,000 psi. minimum
Yield Strength* 3/4” (2.25D & longer) & 7/8 through 1 in. diameter (3D & longer): 45,000 psi. minimum
1/4 through 5/8 in. diameter, 2.25D and longer: 100,000 - 150,000 psi.
Tensile Strength 3/4” (2.25D & longer) & 7/8 through 1 in. diameter (3D & longer): 85,000 - 140,000 psi.

Elongation in 4D* 1/4 through 5/8 in. diameter: 20% minimum; 3/4 through 1 in. diameter: 25% minimum.

D = Nominal diameter of the screw in inches.

•These properties are tested only on machined specimens when the testing machine cannot provide for full testing of the parts.
••Product standards require the manufacturer’s head marking to appear on the top of all cap screws 1/4” diameter and larger. “X” represents one location such
a marking may appear.

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