ISO 4762 specifies the dimensions and tolerances for metric socket head cap screws (SHCS) with hexagonal sockets. These are commonly called Allen bolts or hex socket screws. They feature a cylindrical head with a recessed hex drive.

What is the head diameter of an M8 SHCS?

Per ISO 4762, an M8 socket head cap screw has a head diameter (dk) of 13.0 mm, head height of 8.0 mm, and uses a 6 mm hex key (Allen wrench).

What is the difference between ISO 4762 and DIN 912?

ISO 4762 replaced DIN 912. They are functionally identical for most sizes, but ISO 4762 is the current international standard. Some minor tolerance differences exist on larger sizes.

What property class are SHCS typically?

Standard socket head cap screws per ISO 4762 are property class 12.9 (Rm = 1220 MPa, Rp = 1100 MPa). Some manufacturers also offer 8.8 and 10.9 versions.

When should I use socket head cap screws instead of hex bolts?

Use SHCS when: (1) space is limited and a low-profile head is needed, (2) the head must be recessed/counterbored, (3) higher strength is required (12.9 vs typical 8.8), or (4) a cleaner aesthetic is desired.

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Socket Head Cap Screw — ISO 4762

Look up dimensions of metric socket head cap screws (Allen bolts) per ISO 4762 / DIN 912. Select size to see head dia, height, hex key, and mass.

ISO 4762DIN 912Class 12.9

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Estimated Mass

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Head Diameter (dk)

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Head Height (k)

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Hex Key Size

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Counterbore Diameter (rec.)

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ISO 4762 Dimensions

Size	dk (mm)	k (mm)	Hex Key
M3	5.5	3.0	2.5
M4	7.0	4.0	3
M5	8.5	5.0	4
M6	10.0	6.0	5
M8	13.0	8.0	6
M10	16.0	10.0	8
M12	18.0	12.0	10
M16	24.0	16.0	14
M20	30.0	20.0	17
M24	36.0	24.0	19

Counterbore diameter is typically dk + 1 mm for clearance.

Socket Head Cap Screw ISO 4762 Dimensions | Free Online Tool

Published by Nikolai Shelkovenko on February 15, 2026 February 15, 2026

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ISO 4762 Dimensions