Flat Head Socket Screws

A 90° countersunk head with an internal hex drive, to ISO 10642 and DIN 7991. Used wherever the fastener has to finish flush with or below the surface: sliding faces, mating surfaces, anywhere a protruding head would foul something.

The length trap

On a countersunk screw, length is measured from the top of the head, not from under it. Every other head style in this catalogue is measured under the head. Order a flat head to the same nominal length as the cap screw it replaces and you will be short by the head height. Each listing states this explicitly.

Preparing the seat

The countersink angle has to match the head, and the metric standard is 90° included — not the 82° used by most imperial flat head screws. A 90° head in an 82° seat bears on its outer edge only and will pull through soft material. Check the countersink tool before you cut the seat.

Material

304 stainless. The head on a countersunk screw is thinner than on a cap screw of the same thread, so the socket is correspondingly shallower — seat the key fully and do not over-torque. Cross-reference to ASME equivalents is on the standards page.