Dimensions For Standard Hex Cap Screws

Cap Screws & Bolts – Grades 5 &8
Dimensions For Standard Hex Cap Screws
Head-thread-dimensions-grade5-grade8

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

 Hex Cap Screws      (ASME B18.2.1-1996)
Nominal or Basic
Product Diameter
E F   G H J L  Y
Body
Diameter
Width Across
Flats
Width Across
Corners
Head
Height
Wrenching
Height
Thread Length Transition
Thread Length
≤ 6″ > 6″
 Max Min Basic Max Min  Max Min Basic Max Min Min Ref Ref Max
1/4  0.2500 0.2500 0.24050  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 0.577  13/64 0.211 0.195 0.140 0.875 1.125  0.278
3/8 0.3750 .03750 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 0.689 9/32  0.291  0.272 0.195 1.125 1.375 0.357
1/2 .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 .05625  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  0627 0.591 0.416 2.250  2.500  0.625
1 1/8 1.1250  1.1250  1.1140 1 1/16 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  1 5/16  0.974 0.902 0.640 3.250 3.500 0.833
Tolerance on Length Nominal Scree Size Nominal Screw Length
Up to 1″ incl Over 1″ to 2 1/2″ incl Over 2 1/2″ to 4″ incl Over 4″ to 6″ incl Longer than 6″
1/4 to 3/8 -0.03 -0.04 -0.06 -0.10 -0.18
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
Grade-5 HEX CAP Screw
Description A cap screw made from medium carbon steel and heat-treated.
Applications/ Advantages Has greater tensile strength than a Grade-2. Yield-to-tensile ratio is the lowest of all heat treated steels.
Heat Treatment Grade-5 cap screws shall be heat treated, oil or water quenched, at the option of the manufacturer, and tempered at a minimum tempering temperature of 800°F.
Material Medium carbon steel. Use of an alloy steel is also acceptable.
Core Hardness 1/4 through 1 in. diameter, all lengths: Rockwell C25 – C34. 1-1/8 through 1-1/2 in. diameter, all lengths: Rockwell C19 – C30.
Surface Hardness 1/4 through 1 in. diameter, all lengths: Rockwell 30N54 maximum. 1-1/8 through 1-1/2 in. diameter, all lengths: Rockwell 30N50 maximum.
Proof Load 1/4 through 1 in. diameter, all lengths: 85,000 psi. 1-1/8 through 1-1/2 in. diameter, all lengths: 74,000 psi.
Yield Strength* 1/4 through 1 in. diameter, all lengths: 92,000 psi. minimum 1-1/8 through 1-1/2 in. diameter, all lengths: 81,000 psi. minimum
Tensile Strength 1/4 through 1 in. diameter, all lengths: 120,000 psi. minimum 1-1/8 through 1-1/2 in. diameter, all lengths: 105,000 psi. minimum
Elongation* 14% minimum (all diameters)
Reduction of Area* 35% minimum (all sizes)
Plating See Appendix-A for plating information.
Grade-8 HEX CAP Screw
Description A cap screw made from medium carbon alloy steel and heat-treated
Applications/ Advantages Has greater tensile strength than a Grade-5. Designed for use in high stress applications. See specifications below for more information on how the Grade-8 exceeds the strength of a Grade-5.
Heat Treatment Grade-8 cap screws shall be heat-treated, oil-quenched and tempered at a minimum temperature of 800°F.
Material Medium carbon alloy steel. Note: For diameters 1/4 through 7/16 inch, it is permissible to use AISI 1541 steel.
Core Hardness 1/4 through 1-1/2 in. diameter, all lengths: Rockwell C33 – C39.
Surface Hardness 1/4 through 1-1/2 in. diameter, all lengths: Rockwell 30N58.6 maximum.
Proof Load 1/4 through 1-1/2 in. diameter, all lengths: 120,000 psi.
Yield Strength* 1/4 through 1-1/2 in. diameter, all lengths: 130,000 psi. minimum
Tensile Strength 1/4 through 1-1/2 in. diameter, all lengths: 150,000 psi. minimum
Elongation* 12% minimum (all diameters)
Reduction of Area* 35% minimum (all sizes)
Plating See Appendix-A for plating information.