Metric-Sized Bolt Knobs/Thumbscrews

During a recent repair of a music stand, I needed to replace an M8 thumbscrew that holds the music stand's vertical post. I found suitable thumbscrews on ebay, but was a bit taken aback by their cost. For my own use, I created the M8 version of this knob for use with a regular M8 hex head bolt, but made the design parametric. I include STLs for M3, M4, M5, M6, M7, M8, M9 and M10 bolts, but the attached OpenSCAD code will allow you to generate whatever size you want, as well as customising size, thickness, number of lobes and so on.

The M8 version (pictured) is able to take a surprising amount of torque even just printed in PLA. For strength, extra walls are probably more important than high infill.