The rpm's means little, I do have a variable speed router, but only 15k to 30k, currently running at 25k. I've had better results at this speed with chips.

I did the cut and measure and did it a couple of times and seems to be consistent, 5" gets me 5.002 to 5.004

Not sure on the calculate method how it's done. From the vendor, "The screw is 10 threads per inch, the stepper is 200 steps per revolution, you multiply one by the other and you get 2000. The controller can be set at 1/1, 1/2, 1/4, 1/8 and 1/16 step mode. Your controller is set at 1/2 step mode so you multiply 2000 by 2 and you get the the steps per inch"

So this means I'm at 4000 steps per inch? 1 step = .00025 So I just add or subtract however many steps to equal what I'm off?

I must have measured pretty good, and I learned a major lesson and alot about calibration today! I just recut the file, and I got 1" outer on the pocket and .174 on the inner island!

Close isn't good enough, it has to be correct. I thank everyone who helped me with this! I'm going to cut some other stuff and verify that they come out correctly now as well.

Mark