Knurled Thumbscrew M8×25

An M8×1.25 thumbscrew with a Ø20 knurled head, 8mm tall, on a 25mm threaded shank. The thread is a real ISO 68-1 60° profile — 7.188mm pitch diameter, 6.647mm minor — cut 0.2mm under nominal on every face, so it runs in a printed M8 nut or, at a push, a metal one. The grip is a straight (type A) knurl at 90°, which is ISO 13444's fixed profile angle, at 1.61mm pitch. That pitch is a deliberate departure worth explaining: ISO 13444's own selection table would put a head this size on 0.6mm, and at 90° that is a 0.3mm-deep tooth — narrower than a single 0.4mm extrusion, so the slicer rounds it away and you get a rippled cylinder instead of a knurl. Taking the pitch to 1.6mm, the coarsest in the standard's series, gives a 0.8mm tooth you can actually feel. Note ISO 13444's diameter formulas do not apply here at all: they tell a machinist what blank to turn before a rolling tool displaces the metal into teeth, and nothing is displaced when the teeth are modelled directly. Prints head-down: the knurl is a set of vertical grooves and the thread climbs away from the bed, both in their best orientation. PETG.

from £1.37example, in PLA