OK - here's the problem : Velleman make a 3D printer kit for £700, it is cheap, but nasty. The Z axis is a piece of threaded rod with a standard nut. That strikes me as sloppy by design and I am looking at ways of improving the design by creating a nut with three bits of threaded rod with ends turned to fit into bearings (3x10x4), putting the whole thing together with some end caps so the thing becomes a sort of ballnut that fits on the existing Z axis. I am playing about with the whole idea at the moment. That's what I do (play with ideas, since I lost interest in playing with myself ages ago). I didn't want to go public as the idea may be plain stoopid and I don't want the position of Forum Clown, even if it is vacant.

Having said that the Velleman K8200 kit is crap, it still looks like a cheap way in to 3D printing. You get a lot for the money.

Maybe someone has already done what I am trying out and got far enough to reject the results, or maybe you can buy one from China

Cheers

Rob