Quote Originally Posted by Jonathan View Post
Backlash can cause the effect you describe. It could be something else, like a slightly loose pulley/coupling, but that seems less likely since the rest of the part isn't all over the place. If you're machine is driven by ballscrews then you're unlikely to notice their backlash on wood, since it's very small (<0.05mm). That's not the case if you've used ACME or threaded rod...
That's a worry then as I do have ballscrews! Just got a dial gauge so i will check later and report back :)

Jim