wreck.. I hear ya.. actually it is worse than just that.. the shaft drives a bevel gear which turns the knee acme screw .. when I put it together after removing the shaft there was a noticeable back and forth slop in the bevel gear engagement.. not much and I did not try and measure it.. but noticeable.. im guessing that is my limiting factor.. I did think about putting some sort of spring loaded idler on the chain though I guess it would need two , to handle the 2 directions.. so far im pretty happy with how repeatable it seems.. I did measure my cuts , the program did 100 thou in 5 steps for both cuts returning to safe z of .1 between each step and returning home between the 2 cuts.. I measure a depth of .108- .109 for both cuts.. and this is on a piece of hrs that barely fit in my 6 vice and I intentionally did not face it as I wanted the raw iron look.. and did not take real care in setting the z zero .. so that could easily be off a thou.. the piece most likely was bowed a bit from vice pressure.. anyways when I redo the mounting I may add some tensioners as the chain will certainly stretch over time..
rich
rich