On Thursday, June 4, 2015 at 3:49:56 PM UTC-4, Lloyd E. Sponenburgh wrote:

That works. But I don't own a v-mic in order to do it right. Is there
another 'standard strategy' for measuring odd-number-flutes' diameter?

I've been going through all my old texts, and they all show a v-micrometer
as the preferred method. I was hoping for some old 'shop lore' method.

Lloyd

Interesting problem. I am sure I am too late to be of any help. But have thought of two solutions that might help someone else in the future. One is to make a couple of V blocks. One 120 degree and the other a 72 degree v block. And then a bit to bolt on to the block to hold a micrometer head.. Essentially make a big v mic.

The other is to use a spin index and a dial indicator with a magnetic base. Use a rod of known size to get the dial indicator set up and then put the shank of the cutter in the spin index and do the math to get the diameter of the cutter. But then that is pretty much what you did using the lathe.

Dan