Hello

[Jonathan]

Thanks for the advice I is very mush appreciated, I am getting the message that if buying from china I should go with Chai but for you information the listing I having looking at is http://www.ebay.com/itm/300652998890...ht_3739wt_1037

£400 seemed good for this lot and the ball screws for the X and Y axis are 20mm so whipping should be reduced?

1) RM2005 is more expensive than RM1605 and you only want 20mm screws on one axis, not all.
2) RM2005 has to spin at twice the rpm as RM1610 to obtain the same feedrate and the critical speed of a 20mm screw is less than twice that of a 16mm screw so you'll actually end up with a lower feedrate.
3) Inertia of 20mm screw is significantly greater than 16mm screw so the acceleration and feedrate will be reduced.
4) RM2010 would be worthwhile, but you can only get it in England which is far too expensive particularly for two.

Another question, to make the ball nut housing - if I cut a 36mm hole with a holesaw on my pillar drill into aluminium plate will this be accurate enough or am I best to fork out on ready made ones at £40 a go? (http://www.zappautomation.co.uk/mdg2...ing-p-464.html)

It's easiest to make the hole a little oversize then bolt the nut in the right position so it rests on the flange. That way you get a little adjustment of the centre height to ensure the nut is aligned accurately. Here's some I made earlier: