Make your draw plate out of a piece of 16 gauge stainless, 7 x 2 inches.
Lay out 2 rows of holes - 6 holes per row.
Drill 2 holes (up and down from each other) 1/4, 9/32, 5/16, 11/32, 3/8, 13/32
On the bottom row, use a 4 flute countersink to bevel the edge to paper thin. (the 4 flute countersink has a tendency to chatter in steel, that is why it is good. It will make the exit side of the hole slightly larger that the original and somewhat ragged).
Use the bevelled hole as a scraper (pull a little tension on the scraper, then pull it up and down the shaft, rotating the shaft as you work) and use the clean hole as a gauge.
Stop at the hole just before the one you want, finish with sandpaper and your spine tester and scale.
It works pretty fast after you get the hang of it, so the work goes quickly.
With this setup you can do almost all the shaft sizes and spines you want.
As soon as I get the time, I have some photos of the equipment, plus some other devices I have designed to help in the small shop, that I am going to put on a web page. I'll let the address be known when I get it done, but it looks like it will be next week or later.