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