Posted by noel shelley on 02/02/2022 23:45:23:
18 holes in a 20 circle, 27 holes on a 30 circle, 36 holes on a 40 circle , 45 holes in a 50 circle, 54 holes in a 60 circle. Etc ! Hole circle divide by 10 then X 9 = holes needed to be moved. Good luck, Noel.
Edited By noel shelley on 02/02/2022 23:53:01
S’easy when you know how! Noel is spot on with any one of his multitude of options, but you are maybe trying to start at the wrong end of the calculation.
It does not matter how many times you turn the handle, you just need those extra spaces for that extra 3.6 degrees on top of the multiple of 4 degrees. You would need to turn that same amount 100 times for a full revolution at 3.6 degrees each time.
For 3.7 Degrees, you would need 37/40 of a turn. For 3.9 degrees you would need 39/40ths. For those prime numbers (37 and 39) you cannot use a plate with fewer holes than forty.
Your 3.6 degrees would be for a 100 tooth gear, or whatever you might be machining, so you need a plate hole number that when multiplied by 90 is divisible by 100. End of problem, really, in this instance. 90/100 = 0.9. Any plate which has a hole at exactly 0.9 of the way round will do.
Try it and see. 20 space plate: 20*90/100 = 18. 50 space plate: 50*90/100 = 45
This will be how you can calculate any number of spacings required for any integer-number of teeth on a gear, without recourse to tables on the internet (some of which are known to be incorrect).
I’ve never relied on (or even used) tables as the calculation (for gear cutting) is sooo eesy!
The only difficulty might be for someone to pick which plate circle to use when it is not the same as the actual number of increments you want per revolution. Plates are (unsurprisingly) made for prime number (or multiples of primes) calculations. Seems complex at first but is simplicity, if not easily befuddled by maths.
Think simply – each plate circle is that number as a fraction of 40 (rotary tables with different turns/revolution use the same plates but just different fraction denominators).