Rotary Table Dividing Plates

[Steve Peterson]

It appears that many 4" rotary tables have a 72:1 ratio, while the larger tables have a 90:1 ratio. Here is a link to a dividing plate set for a 4" table that shows different holes than what LEEQ listed above http://saraltools.com/roatry-tables/indexing-plates-for-rotary-tables/indexing-plate-set.html

The holes are
15, 17, 19, 21, 23, 25
27, 29, 33, 35, 37, 39
16, 20, 41, 43, 47, 49

After looking at the numbers in LEEQ's list, it appears that many numbers are common to both sets of plates. LEEQ's list for a 90:1 ratio includes 18 and 31. My list includes 25 and 35. I am guessing that these uncommon numbers are very rarely used, unless you are making a gear with 113 teeth.

Steve

 

[British Steel]

Set your rotary table so that the pointer on the periphery and the hand-wheel dial are set to zero. Rotate the dial while counting turns until you get to 10 degrees. If it took 6 turns, it is 60:1, 7.2 turns, 72:1, 9 turns, 90:1, Easier than walking it all around the block, so to speak.

Ummmm.... no.
6 turns of a 60:1 is a tenth of a rotation, 36 degrees, as are 9 turns of a 90:1, 7.2 turns of a 72:1...
Just crank 10 turns, see how many degrees the table rotates and divide 360 by THAT, multiply by 10 and you have the ratio.

The 90:1 and 40:1 are most common in larger sizes (6" and up) and have the most available plates - Google up the manual for a vertex or soba rotab the same size for a table of hole circles!

Dave H. (the other one)

P.S. the 72:1 ratio is a real pain, only 2s and 3s as factors, which may be why the 25 and 35 holes are in the set, to allow division by multiples of 5 and/or 7 for gearcutting etc.?