Hobbing A Worm Gear On A Lathe, Free Wheeling Method.

[gearcutter]

Necessity is the mother of invention.
The blank would have first been gashed in a milling machine.
The gashes are required so as the hob's lead can pick up on the gashes causing the free wheeling blank to then rotate.
Something that's also interesting in the video is that the hob looks like it has been made from an original worm shaft.

http://youtu.be/C3hXM5jd-pY

Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

http://www.aussieweb.com.au/email.aspx?id=1194181

 

[MikeHalloran]

Damn clever.

I'm curious about how good the gashes have to be, pitch-wise.
I'm thinking that a hob with negative top rake might be inclined to follow the gashes, like a knurling roll, whereas a hob with positive top rake might tend to 'do its own thing' and maybe ruin the gashed blank. ... or not.

I'm guessing there may be a few details not shown in the video.
Okay, I wouldn't show off everything, either.

The machinists are proud of themselves, and rightly so.


Mike Halloran
Pembroke Pines, FL, USA

 

[imcjoek]

I've done some small worm wheels this way using a tap as the "hob".

I think I used a #8-32 tap to cut the "worm wheel" and then the "worm" was a #6-32 threaded rod. Crude, but effective.
The gashes aren't even strictly necessary, but not having them can cause the hob to slip and eat away the teeth that were cut on the previous pass.

 

[JOHNNYWIZ]

Correct indexing has to be performed inorder to have the same pitch