"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 3.70...
"Pete C." fired this volley in news:4dfa2a54$0
:


I think that could introduce errors if the vice is not solidly locked
closed/down. The vise way surfaces with the vice open are probably
better since those are the surfaces your part or parallels supporting
your part reference off of generally.


I think that could introduce some errors beyond that.

Unless you're _positive_, Ig, that the plate itself has been ground flat
to within tenths, end-to-end, you have no way of telling if one end is
high, or there are bellies or waves in it.

You need to tram to the surface of the bed, which at least once was
ground to precision.


Actually, you want to

(1 ) set a known flat surface ( a granite surface plate is typically used )
onto the table, and level it to be parallel to the X and Y TRAVELS using
shim stock or machinist jackscrews while moving the table left /right and
forward/reverse.

(2 ) THEN set a cylindrical square onto the surface plate and make sure that
your z travel is perpendicular to x and y....if it's not, then you need to
shim the collumn or scrape the knee ways before proceeding....

Otherwise, sweeping the spindle in a circle and ****ing around cocking the
head back and forth is basically a crap shoot when it comes to hoping to
obtain better finishes and higher 3 dimensional accuracy.