The Shop > Metal Stuff
Where to get worm and gear 1:40 or 1:60 for indexinng?
drmico60:
Hi Pekka
I would like to make two comments:
1. I would not rule out using plastic gears. These are cheap and light. They are not as strong as metal gears but an indexing unit the usually has some facility to lock the spindle so the gears are under no stress during machining.
2. I would not worry to much about helix angle of the worm. As long as the worm and gear mesh then one turn of the worm will advance the gear by one tooth. This means that you can use an ordinary spur gear for one component and make a worm to match which is a simple turning job. If you make the worm a good size then the helix angle will be small anyway.
I hope this helps.
Mike
Pete W.:
Hi there, Pekka,
Have a look here:
http://www.hpcgears.com/n/products/4.worms_wheels/worms_wheels.php
Usual disclaimer, no connection except that I have used them (for helical gears) in the past. They have an extensive stock range and will also quote for specials.
PekkaNF:
Thank you very much. This helps a lot. I have something realistic to toy with.
I read Gears & Gear Cutting (Workshop Practice Series 17) again and I thought that I'm sorted and then I found this:
http://www.hpcgears.com/pdf_c33/27.48-27.60.pdf
:coffee:
Nope, It didn't cut it. Soo... I eyballed... and questimated and module 0.8 looks about right :lol:
http://www.hpcgears.com/pdf_c33/15.10-15.13.pdf
For a small stepper motor driven indexer, where accuracy is important, but not much forces are expected. Unless they have no-thank-you p&p price looks right too.
For middle size lathe I would need MOD 2 would clear spindle - and my wallet! Way over 100 GPB. That would require careful consideration.
They have a "budget" model too:
http://www.hpcgears.com/pdf_c33/21.5.pdf
Price is right, but really MOD1 would be too small in 1:40 gear ratio. Even nonstandard biggest 50 tooth wheel would not clear even the smallest lathe spindle I have.
How much compromize really I would be looking at MOD1 60 teeth straight spur gear coupled with MOD1 1 start worm?
http://www.hpcgears.com/pdf_c33/23.28-23.33.pdf
OK, I know putting it to oil bath and using it for circular milling is out of question, but when it comes to indexing would I loose on accuracy?
If I get it right worm should be at lead angle (MOD1 - 3°35´) to wheel? MOD1,5 looks like a good possibility.
Pekka
chipenter:
I would go for a 90 tooth wheel gives you 4 divisions on the indexing per rev , and greater accurarcy and more divisions with youre plates .
PekkaNF:
Thanks. Now I only need to aproximate what I want :lol:
I basically have two more immediate needs: To index few dials for lining (probably something 40-100 divisions) and simple division plate on lathe (maybe 60 or 24 division?).
If I get it right, it does not make much difference between 40/60/90 tooth wheel and and a single start worm when it comes even divisions?
I have a set of indexing plates, arms and handle for 1:40 ratio (Plate #1 has 15, 16, 17, 18, 19, and 20 holes. Plate #2 has 21, 23, 27, 29, 31, and 33 holes. Plate #3 has 37, 39, 41, 43, 47, and 49 holes). Therefore I was rushing into 1:40 division.
I have to check the divisions, but I don't think I'm missing any small divisions, no matter which 40/60/90 ratio I take.
Pekka
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