Face mill finish

[Edward]

I don't understand the first test. It seems to measure bed flatness, it does not depend on the column being vertical to the bed.

The indicator holding prong is actually in the spindle, held inside an 8mm collet. The measuring lever is just touching the table. Therefore any readings of the table are relative to the spindle/head/column assembly. Since the only thing that moves is the swipe east to west of the table, , the reading will change if the table is not horizontal.

Then repeat for north to south travel, using a long parallel across the table to serve as a flat surface for the indicator to slide on.