Worm gear hobbing question

[Dfennell]

Question about calculations for worm gear hobbing...

I'd like to try hobbing a few worm gears and would like to know how to calculate OD etc. I've found the GearSpec program from W.M. Berg http://www.wmberg.com/ but the deal is, I'd like to use a 1/10 pitch .500" Acme screw for the worm. I know this isn't a true worm, so the question is - is the data provided by this program close enough to create a servicable worm gear using the Acme threaded rod?

PDF attached with worm gear data

[Les A W Harris]

Dfennell,

"I'd like to use a 1/10 pitch .500" Acme screw for the worm. I know this isn't a true worm,".

It is a true worm!
The Berg Data is for Fine pitch worms, the P.A. is fixed at 20*, You need Industrial wormgearing, Machinery's Handbook has the equations, P.A.'s range from 14.5*(Acme Thread form) to 30*, So you have to crunch a few numbers & you're ready to do it!

Got more medical appointments, will be back to check on you,
Happy Worming!

Cheers Les H.

[Dfennell]

Thanx les, I need to get a copy of the book anyway :-)

[HuFlungDung]

The chart looks about right to me.

One thing to help avoid confusion: the description of diametral pitch in your chart is listed as 1/10" pitch. That is actually your circular pitch. The equivalent diametral pitch for that is about 31.416 Dp. Just telling you this in case you get a notion to purchase some kind of tooling and get perplexed when it it 3.14159 times bigger than you expected