Quote Originally Posted by dazp1976 View Post
Otherwise you may have to get some proper expensive grounded C3-C5 type screws. And angular contacts to fit them.
There's no point buying expensive ballscrews unless the whole machine is built to the same very high standard.

To be honest it makes me laugh when I see figures quoted in the 0.001 range or higher from DIY builders because they are just fooling them selfs. Just leaning on the bench while measuring will affect most DIY machines as it deforms to match the bench movement at this level or precision. Measurments taken in the morning will be different than in the after noon and as the machine heats up, most don't even own measuring devices that are calibrated to that level.!

I've got precision ground granite table and calibrated granite squares etc with calibrated measureing devices and wouldn't claim or expect those kind of precision from a bolted together aluminium profile or a welded steel framed machine that hasn't been heat treated and had machined surfaces etc.

Precision of 0.01mm is about as good as you should expect from a DIY machine with C7 screws and bearings. Even then only expect this over a short distance because the thread pitch will vary over the length. Anything above this is a bonus and will most certainly vary over a length not much more than 300mm.!

Keep it real folks, then you won't be dissapointed.