Fasteners — Hexalobular socket countersunk flat head screws (common head style) with reduced loadability

This document specifies the characteristics of hexalobular socket countersunk flat head screws with reduced loadability due to head design, in steel and stainless steel, with metric coarse pitch threads M2 to M10, and with product grade A.

If in certain cases other specifications are requested, stainless steel grades can be selected from ISO 3506 1, and dimensional options from ISO 888 or ISO 4753.

NOTE 1 The reduced loadability (related to the countersunk head dimensions in combination with penetration of the hexalobular socket specified in this document) implies a limitation of ultimate tensile load shown by a specific marking (property class preceded by a zero). The loadability in the head is assumed to be 80 % of that in the thread for all sizes and all property classes; see Table 3.

NOTE 2 Hexalobular socket countersunk head screws (high head), with full loadability are specified in ISO 14582, but these products are not interchangeable, because of different head heights.

NOTE 3 Particular attention is needed to ensure alignment of the countersunk head with the bearing surface of the countersink in the assembly.