Screw: hexagon socket button head

ISO 7380-1

ISO 7380-1 - Hexagon socket button head screws with reduced loadability

Hexagon socket button head screws with reduced loadability, in steel and stainless steel, with metric coarse pitch thread, product grade A. The screw is driven by a hexagon key seated in a socket sunk into a low domed head, and the head rests on the surface of the part instead of being buried in it: the part needs neither a counterbore nor a countersink, and the rounded top leaves no edge for a hand or a cable to catch on; this is what holds covers, guards, panels and brackets too thin to be counterbored. A size is the pair d x l: the thread diameter fixes the head diameter dk, the head height k, the socket size s and the key engagement depth t, while the length decides whether the screw keeps a plain shank or is threaded up to the head, and with it the radius under the head, which is larger on a screw threaded to the head. The head is wider and about half as high as the head of a cap screw of the same thread - 10,5 mm across and 3,3 mm high on M6, driven by a 4 mm key instead of a 5 mm one - and sinking the socket into so low a head is what limits the load the screw can take: the minimum ultimate tensile load of a size is 80 % of the load of a fully loadable screw of the same thread and property class, which the marking shows by a zero in front of the property class, as in 010.9. The reference thread length b is 2d + 12 mm up to M12 and 3d on M16, raised in 2022 so that a partially threaded M16 can still be tensile tested. Covers threads M3 to M16 with nominal lengths 6 to 90 mm. The variant with a collar under the head is ISO 7380-2.