Today I attempted to machine a nice concentric M12 worm.
I first turned a nice std M12 thread and turned a clear
shank both ends. I decided to make it standard rather than
ACME to make it match the gear. ACME can come later.
Bored it out to fit snugly on
this little worm assembly that
had some purpose built thrust/end play bearings.
You can see the original worm sitting beside it.
The idea here was to set it all up on my shed bench and
run it for an hour or so and feel the play/slop/eccentricity
in the whole setup.
I screwed the spindle and HD platter gear down to the bench first
then meshed in the worm until it was on centreline and snug.
I drove it around a bit first using a battery drill to check
concentricity of everything and see if it hadn't bound up
anywhere.
Next I bedded in the M12 worm with the worm wheel
using a 24AC motor/reduction gearbox and small chain and sprocket.
Some cutting compound every now and then was added.
The gear was SOOOO smooth and had absolutely nil slop.
After driving itself around in both directions for about an hour there
was no slack or backlash present.
With some light grease on it, it was very quiet too!
Steve