On 18 Apr, 17:09, Danny Richardson wrote:
On 18 Apr 2007 14:17:27 -0700, art wrote:

I've never seen a 'spirit level' being used in a tool room for
accuracy nor could I specify from what you said as to why it should be
used from now on instead of conventional means.

Well, I guess you haven't had much experience in the tool room.
Otherwise you would have been aware of how precession levels used to
set up machinery. They are used often. How do you think those long bed
lathes are adjusted so they are straight, level and parallel? Yes, my
poor misinformed person they use precession levels.

Danny, K6MHE

Danny,
don't be silly, you obviously have not spent a lot of time in a tool
room.
A tool room machine is not in any way used as a reference level. What
is used as a reference level is the machine slide with reference to
the cutting plane. An installation of a machine is subject to settling
but it does not affect the accuracy of the product.
Use of a spirit level over the use of a straight piece of angle as a
reference plane is rather stupid and impracticable.