SHCS stands for socket head cap screw, the cylindrical, knurled-head screw with an internal hex drive that fills tooling, fixtures and machinery. Alloy steel versions are heat treated to roughly 170 to 180 ksi minimum tensile in inch sizes, or property class 12.9 in metric, and usually carry a black oxide finish. The head is about one and a half times the thread diameter, which lets screws sit close together in counterbored holes.
Fixture plate gets M8 SHCS in counterbores, twelve-nine, and torque them, don't just lean on the T-handle.
Alloy socket heads are among the strongest screws in any bin, so a broken one in a fixture usually means something else went badly wrong.
Also heard as
- socket head cap screw
- socket head
- Allen bolt
Related terms
Allen key
Shop name for an L-shaped hex key used to drive socket head cap screws and set screws.
Cap screw
A precision-headed screw, hex or socket, made to close tolerances and usually driven into a tapped hole.
Property class
The metric strength grade of a bolt or nut, stamped on the head as a number such as 8.8, 10.9 or 12.9.
Class 3A/3B
The tightest standard inch thread fit, with no allowance on the external thread, used for precision hardware.