Thanks for all the advice, Taken it all on board. From looking on here and the CNC zone I always planed to use servo motors, linear rails and ballscrews for the main machine, and now I know why.....

Still all good practice, dont know If I can justify ballscrews for this one. No point in having an ultra precise table if the head flexs all over the place. May be I should just get it working and then if its just the backlash thats an issue, I can sort it then.

Made the tap tonight and tried it on some plastic I had kicking around. Worked fine but I think the plastic is to springy and the tap wont cut the last bit for clearance, very tight over a 40mm length. Ive tryed tapping fuild and a drill but the end result is a very hot and shiney leadscrew, Still at least I know the best way to polish them now :clap:. I'll have to order some delrin,or try narrower sections.

Changing the subject, what is the best way to hone the dove tails on the slides? I've got them really smooth, with no play, except for the the first 30mm or so where i can feel an bump, Cant get the oil stone in and dont want to over do it by using a grinder.....If I carry on lapping it will both parts wear and then cause problems over the whole length?

Thanks again