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How does one scale a worm gear?

Would like to replicate a worm but 3 times smaller.

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William S01/07/2020 00:08:45
26 forum posts
134 photos

Evening all

So armed with the above information I have had a go at hobbing a worm wheel.

Began with grinding a 20degree pressure angle single point tool(done on the little d bit grinder takes a bit of faffing about the get the clearence angles!); dsc00156.jpg

Then I set the lathe the cut the hob, 64dp which meant swapping the input gear for a 33t. The hob screwcut, then some cutting edges formed with a slitting saw. Couldn't find a piece of 8mm silver steel so I used a piece of printer rod, I haven't harden it as it was only a test;dsc00152.jpgdsc00146.jpg

On the shadow graph at work just to see what it it looks like, not bad if I say so myself!; dsc00142.jpg

The lathe set up to hob the wheel (not the best I know); dsc00153.jpg


First test went well, an old chopping board was the material only issue was not making it single enveloping and not gashing caused 179 teeth;dsc00155.jpg

Final test achived the magic 180t (gashed with a slitting saw) and a single enveloping wheel;


So all in all not bad, totally doable I reckon, I will now refine the hob in silver steel, harden then have a go in a piece of metal!

I think I will now take the time to do some drawings of the BCA, I might start a thread when I come to do my model for those who are interested.

Many thanks for all the input



Edited By William S on 01/07/2020 00:11:15

Edited By William S on 01/07/2020 00:12:13

Michael Gilligan01/07/2020 06:26:04
15768 forum posts
689 photos

Great start, William yes

I look forward to following your progress


Howard Lewis01/07/2020 10:37:10
3289 forum posts
2 photos

A really good effort! Well done


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