Odd dividing plate

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Phil Pascoe

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I've seen advertised on Homeworkshop a dividing plate with 61 holes - the chap has double checked, it's definitely 61 holes. What on earth would be the purpose of one with a prime number of holes? Anyone a suggestion?
 
The most useful dividing plates are those with Prime Number rings. It's easy to divide many even numbers, Primes are the difficult ones and often needed for both Screw & Gear cutting.

Without a 61 hole plate it's very difficult to make a 61T Gear - I don't have a solution in my Gear-hobbing spread-sheet for 61 - - - but neither do I have for 37, 41, 47, 59, 67, 73, 79 . . . . . .

There are solutions, but they all require you to have an existing 61T or 122T gear. Oh yes, to make a 122T gear you also need an existing 61 or 122!

To make a 61 hole plate you need a dividing head that can advance accurately 5.901639344°, most advance 4° per turn so that would be 1 turn plus 0.475409836 turn.

With a 61 hole plate you could easily make a 61T and thence a 122T Gear.

I solved my problem for a 37T gear by using my CNC machine to 'engrave' it, as I did for the 41T.

I've also counted the holes in the plate in question and can confirm that it is 61.
 
Last edited:
From distant memory aren't the odd number dividing plates used with more rotations to achieve finer divisions of the index.
I could be well off the mark.
geoff
 

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