azotic wrote:

Anyone ever try this methode. It seems simple and quick.

http://www.youtube.com/watch?v=ZfioLDhBNBQ
Well, if the top of the table has any dings, the disc
sits on top of them and may give a bad reading.

What I do is mill the top of a piece of stock with a relatively
small (3/8") end mill. I then indicate a ring of this with
a dial test indicator mounted to the spindle. This compares
the spindle with the XY "plane" of travel of the mill, not
the top of the table. The plane of XY travel is what is REALLY
important, and you can't be sure the table is parallel to that.

My ancient Bridgeport has wear on the ways, and so it does
not travel in a perfectly straight line, there is a slight
arc to the travel. It also has enough dings on the table
that it is iffy to indicate off that.

Jon