My plates are as listed:15,16,17,18,19,20. 21,23,27,29,31,33. 37,39,41,43,47,49. My rotary table, however, is a 90:1. To find the proper plate/turns without a table or chart one would divide 90 by the desired number of divisions. Let's use 22. 90 divided by 22 is 4 with a remainder of 2/22. The denominator needs to meet a plate you have, so you need to adjust the fraction. 2x1.5=3. 22x1.5=33. Or 3/33. That works. Using a 33 hole plate one would turn 4 turns and 3 spaces. All that is to illustrate that a set of plates for a 72:1 is liable to be different than sets for other gear ratios. The hole numbers being set to work/divide well with the ratio.You have one plate so you know everything except numbers. I would look up sets for sale geared the same and see what they have. If the small plate matches up with yours, the others hold your answer. I hope that makes sense, and Best of luck.
