Friday, 26 June 2020

Printing Pinion Gears for the mini lathe.

I managed to strip one of the pinion gears on the mini lathe a while ago and I was surprised that I couldn't find a 3D model of them to print, particularly as I'd seen a lot of gear wheel sets for the mini lathe on thingiverse and elsewhere (I think this is an indicator that perhaps other people aren't as idiotic as me and don't strip their pinion gears)!

 Today I set about sorting it with some 3d printed replacements. I used the involute gear tools in the "Part Design" workbench of FreeCAD which I am using more and more as my go to CAD environment. It's a pretty easy tool to use so long as you know the "module" of your gear which can be worked out as it is the pitch circle diameter divided by the number of teeth. Counting up the teeth on the old stripped gears showed they were a 25 tooth and a 20 tooth and the overall diameter was close enough to make me feel that the pitch diameter was going to be the number of teeth in mm giving a module of 1. I'd read online that the mini lathe gears all ran at 20 degree pressure angle. A quick bit of calliper work on the hole diameter and we were ready to CAD!

The results are great, printed in PLA at 35% infill I've been running the gearbox for a couple of hours and all seems well. I've printed up a few spares and chucked them in the box of gears. As I couldn't find this set of gears online anywhere I've put it up on thingiverse as a project so hopefully it's of use to others. You can find the files and the print settings here. 

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