Socket Cap Screw / Allen Bolt (DIN 912 / ISO 4762)
Socket cap screws (commonly 'Allen bolts' after the Allen drive) are high-strength precision screws with a hex-socket drive in a cylindrical head. The high property class (typically 12.9) and clean head profile make them the default choice for machine assembly, jigs and fixtures, and any application where space is limited but high torque is required.
Specifications
| Standards | DIN 912, ISO 4762, ANSI/ASME B18.3 |
|---|---|
| Property Class | 12.9 (standard), 10.9, A2-70 / A4-70 stainless |
| Diameter | M2 – M30 |
| Surface Finish | Black oxide (most common), Plain, Zinc plated, Stainless |
| Drive | Hex socket per DIN/ISO |
Frequently Asked Questions
Why are most socket cap screws black?
The standard black finish on Class 12.9 socket cap screws is black oxide, a thin conversion coating that provides modest corrosion resistance and the characteristic appearance. It's not a heavy plating — for outdoor or corrosive service, choose zinc-plated or stainless variants.
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