Flat Head Cap Screw

A flat head cap screw is a socket screw with a countersunk head. It sits flush in a countersunk hole and clamps parts together.

A flat head cap screw sits flush in a countersunk hole and leaves a flat surface after tightening. It takes a hex key of the matching size and often a nut or a tapped hole of the same thread. The head needs a countersunk seat cut to the same angle so the screw sits level.

This kind of screw is often made in stainless steel 304 or stainless steel 316. Grade 304 suits general use. Grade 316 gives better resistance to salt and chemicals.

This is a general guide to checking this kind of part. It says nothing about any supplier's parts.

Ask for a certificate of conformance with the material grade and dimensions. On receipt, check the head angle, socket size and thread form. Check that the head sits flush in a matching countersunk hole.