Axle hole primitive on a Bar connection.

[Philippe Hurbain]

You just gave me a headache even bringing up the subject. Then we'd have to comb the library for every part that has an axle hole but doesn't use a primitive for whatever reason.

If we ever do that (and I am NOT advocating for this, scares me out of my wits!), axle should be modified too to make the sides fit 22.5° vertex of R6 circle. Not only this could make primitive substitution work better, but also would fit better the physical shape. Axle fins are 1.8mm thick (currently modeled at 1.6). Using 22.5° vertex would make it 1.836mm. Much closer...