# Indexing a 100 tooth gear



## H. K. Barrows (Apr 30, 2011)

Helo Folks. I'm running around in circles trying to make 100 tooth 32 pitch gear with 72- to- 1 R/T with 15 and 28 hole plates. I'm very slow with math, given simple gide lines and an example to work with this will hell me to learn, and put in my book of learning. Thank You. RED


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## steamer (Apr 30, 2011)

100 holes in a 72 hole plate

50 holes in a 36 hole plate

25 holes in an 18 hole plate

I can't come up with anything with a 15 or 28 hole plate

Sorry

Dave


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## mklotz (Apr 30, 2011)

I think Dave got himself turned around.

It's turns = ratio/(divisions desired)

so we have:

72/100 = 36/50 = 18/25

or

72 holes on a 100 hole plate,
36 holes on a 50 hole plate,
18 holes on a 25 hole plate.

Red, you may want to think about downloading the free DIVHEAD program from my page.


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## MachineTom (Apr 30, 2011)

Red, what you could do, is make a blank plate, or if there is room on yours, then ask a member here to drill x # holes in said plate you would provide. Sure to find someone to offer help.


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## BillC (May 1, 2011)

I have a CNC mill that loves to drill holes.....needs no supervision, will work in the dark, doesn't drink any of my beer, and does not complain about drilling lots of holes. We would be happy to make a 100 hole plate for you....

BillC


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## steamer (May 1, 2011)

Marv's right...sorry about that.

Dave


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## Maryak (May 1, 2011)

If you don't have a plate then perhaps you could use the degrees and minutes method

i.e. 100 divisions = 3.6o per division, (360/100)

or 3o 36'

Set the RT table dial to zero, move 3.60, lock the table, cut the gap, reset the dial to zero, unlock the table, move 3.60, lock the table, cut the next gap and so on.

As a matter of interest, in the case of a 72:1 worm ratio 1 turn = 5o (360/72), 15 holes = 1 turn which = 5o. 

so 1 hole = 1/15*5*3600 = 1200"

28 holes = 5o

so 1 hole = 1/28*5*3600 = 643"

It sometimes helps to break down all your dividing plates into seconds of arc per hole as quite often it is possible to compound index on a dividing plate to get the desired ratio.

Hope this helps

Best regards
Bob


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## tel (May 2, 2011)

Or none of the above. For a 100 tooth gear I would use a change-wheel set up, a 2:1 reduction pair (say 30/60) with a 50t keyed to the 30t, then just run around the 50t twice, indexing at every tooth. Might not apply with your equipment tho!.


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## H. K. Barrows (May 2, 2011)

Hello Folks. What a great bunch of replys. THANK YOU ALL VERY MUCH. I bought a r/t a few years back on an impulse it was at a H-F parking lot sale left it in box on a shelf untill I read you'r replies, I just looked at it, supprise the thing has a hole plate with with 25 holes, just set it up looks like it's going to work for 100 tooth gear. Best Regards. Red


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## steamer (May 2, 2011)

Well ...there you have it sports fans!


 ;D

Happy indexing!

Dave


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