Thanks for the quick replies guys! Thanks for all the info jazzcnc, I have a lot to learn.

I have followed your advice and I think there might have been a couple of solutions in both posts.

I had a look and some of the connections in the terminals of the drivers were looking a bit strained, so I pulled the cable back to relieve the stress. Hopefully that'll minimise any noise.

I also had a look at the movement speed that was set on the tools ( the guy that we got the machine from gave me this advice too after I'd posted here ) and the plunge and movement speed was set pretty high, and could well be causing the machine to miss steps as you suggested John. It does seem odd that it was pretty much exactly 10mm every time, so what you say makes sense.

Having done all that, the machine seems to be behaving itself! Thanks very much! I'm looking forward to being part of the forum.