Here’s some photos of a vertical transmission that I made some years ago that I have ‘retrohobbed’ one side of the drive pulleys on this morning.

G’day Michael, knurling like that would be beyond my paygrade (well and truly).

This is very gentle, the drive wheel being hobbed automatically turns by the action of the tap spinning (for me the lathe at 400rpm is perfect) and you can let it go around as many revolutions as you’d like slowly giving more depth to the cut.

I’ve found that once you are at the preferred depth, I let it do 3-4 revolutions until the tap is no longer removing any material. I then put the piece on a mandrel and use some very fine wet & dry.

Thanks Michael.

Retro Hobbing…..(Worm Gearing) I’ve been busy hobbing my vertical and horizontal transmissions I made some years ago plus a few other accessories.

Things I’ve learned from doing many now – what works for me.

Lathe 400rpm
Use lots of WD40 and a toothbrush to keep clearing away the chips
Very critical is to have the tap centered perfectly in the middle (spend some time eyeballing this) if there’s any chatter whatsoever the tap is either trying ride up or down
Don’t put too much pressure on the tap, its not needed and just keep going in a couple of thou at a time. When you’re at the depth you want, let the piece rotate at least another 4x for a really clean cut.