Some time ago, there was a post describing how to check the actual angles of V bits. Also, some time ago, Bill Korn and I found that some 1/8" mills that we were using on a joint project were not really .125" in diameter. Some were closer to .118".
Frequently, on this forum, there are questions about how accurate the Mill is. Users create gcode for a 4" square for example and find that when they mill it out, it is not precisely 4". Many Mill owners are looking for accuracy down to .001" or better, which, with wood that moves with humidity and stress relief is a tall order at the best of times. Combine that with bits/mills that may not be precisely as advertised and it’s pretty much impossible to achieve.
Today, for giggles, I tested 3 different 1/4" end mills - a down cut, an up cut and a single flute. I simply fired up the router and used the jog keys in gSender to route two grooves with each mill - one in X and one in Y. None of the grooves was precisely .25" wide. They ranged from .235" to .246".
I just thought that I would throw this out there for anyone seeing that they are not getting the precision that they would like from the Mill. When Bill and I were doing our project, we both simply entered the correct mill diameters into our respective CAM applications and things worked out.
I assume that can be done in any CAM application, but I can only speak for VCarvePro and Fusion.