Heatset Insert

Heat-Set Insert cuts the pilot hole a brass thermal insert melts into — the cheapest way to give a printed part a real metal thread you can screw into hundreds of times without stripping it. Pick the metric size, from M2 to M10, and it bores the recommended pilot diameter and cuts a 45-degree lead-in funnel at the mouth that squares the insert to the axis as the soldering iron presses it home. The pilot is deliberately smaller than the insert's outside diameter, because it tracks the knurl-root diameter rather than the OD. As the brass heats and sinks, the knurls displace softened plastic that reflows around them and locks the insert in place. Too large a hole and the insert spins under torque; too small and it squeezes plastic up and out around the flange. Those numbers are what the size enum encodes, so you do not have to look them up. Bore depth is yours to set — match it to your insert length — and Fit biases the diameter per side, because heat-set inserts vary noticeably between brands. Set the bore depth to your insert length plus about 0.5 mm of relief so displaced plastic has somewhere to go and the insert seats flush. Make the surrounding boss wall at least as thick as the insert OD — twice is safer — so it does not split, and install square from the chamfered side, letting the iron do the pushing.