Picked up a nice desktop CNC mill with ball screws and servos that looks like it could be commercial rather than a conversion. Looks to be about 1980's vintage. The ball screws are 5 TPI as close as I can measure and the encoders are 100 line. Given 4x decoding of the encoders that gives me 0.0005" resolution. I have another small ballscrew mill of similar vintage (but not similar construction) that has significant belt reductions so something like 40,000 steps per inch. Just wondering what resolution most conversions have. Without microstepping it would seem like most would be close or slightly smaller than the 0.0005" of the first machine. Also, what is typical/realistic for accuracy? Clearly the second machine has much more resolution than accuracy. I am thinking 0.0005" while not tool and die shop type resolution it should be more than adequate for most things.