On Sat, 17 Mar 2012 20:26:54 +0800, "Dennis"
wrote:

when I do a 1mm move sometimes I see 0.90mm or
0.95, sometimes 1.0

That is a massive 10% error. It might not be visible to the naked eye,
but it can't be far off. If you examine threads with a plain thread
gauge, you should easily be able to detect such large errors.

I don't know how accurate allthread is supposed to be, but I cannot
possibly imagine an error this large is within specs.
--
RoRo