Knob for socket cap-head screws in M3, M4 and M5

This is a remix of my M3 screw knob design that seems to be quite popular. I have tidied up the code, made it more reliable to print, and expanded it to cover M3, M4 and M5 socket cap screws.

It comes in two flavours: using either a standard nut, or a nyloc nut. In the pictures, the white knobs have standard nuts, and the red have nylocs - note the slightly greater height. The standard nut is easy, and usually very secure. If you feel the need for a more reliable knob then you can use a nyloc nut - but be aware that it is a struggle to fit onto M4 and M5 (M3 is fairly easy). I recommend that the nyloc nut is wound down as far as possible using a spanner/wrench, then pushed into the hexagonal cavity and the screw wound home; the problem is that it's very difficult to hold onto the knob at this point. It will be necessary to hold the outside using a vice or pliers during this process, while trying not to damage the surface.

If you want a secure fixing without the hassle, I recommend using a standard nut and some thread-locking fluid.

Parameters such as knob diameter, number of grooves around the outside, and so on can be easily changed in the OpenSCAD code. The chamfer.scad library can be found at https://github.com/SebiTimeWaster/Chamfers-for-OpenSCAD/blob/master/Chamfer.scad

I used 0.2mm layer height, 25% infill, in PLA+. However, you can use whatever settings and materials you are most comfortable with.

Originally I tried printing with support, but found that it was very difficult to get the support material out of the lower cavity. In the end I printed without it, and found that the parts only needed a small amount of clean-up before use.