Hul Tytus wrote:
rec.crafts.metalworking
measuring play in quill+spindle of milling machines & drills

I'm hoping that some here have measured the play in the quill+spindle
of bridgeport & equivilent millers, which will be a deciding factor when I
buy one in the future.
The measurements that I have made were by chucking a 10 inch piece of
bar stock and pulling 10 lbs left then 10 lbs right at the end with a spring
scale with the quill lock, when present, loose. A dial indicater set on the
spindle indicates the play.
A small bench size drill press, a $60 version, showed 13 thousandths
of an inch play, 8 for a full size and heavier drill press, and 5 for a
spanking new mill/drill from Harbor Freight. The last omitted the scale
which leaves it a bit questionable.
If anyone has made equivilent measurements, posting the results
here would be greatly appreciated.
I cobbled a massively abused Bridgeport 1-J head onto my ancient
round-ram Bridgeport mill some years ago. I did some checks on
it when I was done. I got about .001" total back and forth
movement when pushing about 50 Lbs one way, then the other way
on the spindle. I was measuring with a magnetic mount indicator
stand clamped onto the main head casting, so I was only
measuring quill+spindle radial play, not any flexing of the head
to base component stack. This amount of play is the
displacement of oil from the bearing balls, and will be zero
when the bearing is spinning. I can't find any movement at all
in the quill. Unless horribly worn, the Bridgeport quill is a
very fine fit, and rarely gets loose. The spindle bearings can
get worn out, and they can be pretty expensive ($300 - 700 a
set.) But, it is much easier to check them by listening when
they are run. If they sound rough, diesngage the direct-drive
clutch and try again. The motor and backgear bearings are cheap
and easy to replace, so don't reject it is only the small
bearings are noisy. You can spind the spindle by hand when the
direct-drive clutch is open, and then ONLY the spindle bearings
will be turning, so if it sounds OK then, it should be fine.

Jon