I did not say they wont be accurate if mounted properly. I'm merely pointing out that most people don't mount them properly, and thus don't obtain the best possible accuracy. Nowhere have I said it's a good idea not to mount them properly.

We both already knew everything either of us has posted in this thread, so the only purpose in discussing is to let others know. Spreading the knowledge is the whole purpose of this forum, hence I discuss.

Your lasts post seems to be suggesting the reference edge of the master rail is perfectly straight? Which is surprising, as this simply is not true. The point of the reference plane on the rail is that is it parallel to the grooves the balls run in - you can't easily indicate off the grooves but can use a plane. You have to first straighten the master rail when mounting by attaching a bearing block and indicator and using a genuine straight edge as the reference for the indicator, or by clamping the reference plain to the straight surface.

Hiwin's document on the subject explains it all perfectly clearly, well worth a read:

http://www.hiwin.de/DownloadCenter/f...9TE14-1006.pdf