Bolt: hexagon head

ISO 8676

ISO 8676 - Hexagon head screws with metric fine pitch thread

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Hexagon head screws with a metric fine pitch thread instead of the coarse thread of ISO 4017, fully threaded, product grades A and B. The screw is turned by a spanner on a hexagon head and is threaded over its whole length, so one size fits any grip and it can be driven into a tapped hole to any depth. A size is the thread diameter, the pitch and the length, as in ISO 8676 - M20 x 1,5 x 80 - 8.8: M10 is made with pitches 1 and 1,25, M12 with 1,25 and 1,5, and M18, M20 and M22 with 1,5 and 2, each pair sharing the head. The head is the head of ISO 8765 value for value: the thread diameter fixes the width across flats s, the width across corners e, the head height k and the bearing face dw. The thread reaches the head but for the run-out under it, which the standard limits to a max = 3P, so the guaranteed thread length is l - 3P. The length decides the product grade, which is the close grade A up to M24 and 150 mm and the medium grade B beyond either. The range of standard lengths follows a rule instead of a table: from 2d rounded to the nearest nominal length, 120 mm for M64, up to ten diameters and never above 200 mm - a longer joint takes the partially threaded bolt of ISO 8765. Covers threads M8 x 1 to M64 x 4 with nominal lengths 16 to 200 mm, in property classes 8.8, 10.9 and 12.9 up to M39 and in stainless steel. Its German predecessor DIN 961 was replaced by DIN EN ISO 8676, which changed the widths across flats of M10, M12, M14 and M22; the partially threaded counterpart is ISO 8765 and the coarse thread version is ISO 4017.