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 low domed head has no collar, unlike ISO 7380-2. 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.