rec.crafts.metalworking
measuring play in quill+spindle of milling machines & drills

Ned & Jon - The level of tightness in the quill/spindle of these machines that
you both are stating is impressive. Jon's finding of 1.5 - 2 thou for 50 lbs
both ways measured from the table but moved from the floor looks significant.
As a guage, a C made from a 4 foot steel 2x4 would show a deflection
of 4 thou with 10 lbs in & out. Surely a miller, with such masive castings,
would make a better show. But, with the number of joints between the cutting
tool and the table, there is room for Murphy. Especially, as Jon mentions,
when the lead screws are considered.
Actually, locking the various movements and then measuring might be an
effective approach. Provide a measure of the foundation, so to speak, then
consider the leadscrew, which would probably lead to inertial & harmonic
calculations fairly quickly.
Ned, if the tool is tight as it should be, then you are most likely
correct about the use of such a measure as an indicator of expected
tolerences; but if the ways are worn or the gibs are gimped or something
similar then maybe not. Jon's last mentioned measure provides an indication of
what could be expected, which is useful. Perhaps mostly to avoid buying a
marginal tool.

Hul