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Splitting the threaded bolt from the handle was mostly the result of wanting this to print without any supports. The slopes on the thread are different on its two faces, one is angled and the other nearly flat. Printing with the sloped face downwards avoids the need for any support, while printing with the flat face downwards would imply supporting the entire thread (and that would almost certainly fatally compromise the thread mechanically, in addition to being a pain to clean off).
Given that the thread itself has to be printed with the handle end uppermost, incorporating the handle with the thread either means having the underside of the handle supported (which is quite a lot of support material for that area and at that height above the print bed) or making the underside of the handle conical. As I said, I did not want any supports to be needed for this design so that ruled out the former. The latter was ruled out because I wanted a wheel-like handle rather than a bulky knob handle for aesthetics, and to keep the overall size/length down for storage.