Re: [CAD_CAM_EDM_DRO] Bridgeport 2J-2 Head Noise

vavaroutsos wrote:

>There is a resonance in the head of my BOSS 6 milling machine that
>occurs at medium to high speeds and causes a knocking noise. The
>noise appears to come from the spindle pulley area. It happens even
>with the gear box in neutral, so I think the gear box and spindle
>bearings can be ruled out. The three upper head bearings are new, as
>well as the spindle pulley hub and brake bearing cap. Everything
>seems tight. Anyone have any ideas as to what the cause might be?
>
>

Let's see, with both the direct drive clutch and the back gear in
neutral, the only things
turning are the motor, driven pulley and the back gear input shaft. Is
it really a
resonance, or a noise when the vari-speed drive is set to a particular
position?
If it is really in the vari-speed (which I think is pretty likely) you
should be able to
make it knock, then shut the motor off, and get some small click-click
out of it
by turning it manually. Also, you should hear it keep clicking as the
motor spins
down. If it is the vari-speed, I'm no expert there, but there are some
plastic bushings
inside the movable pulley sheaves that wear out, and will wreck the
shafts if they
are allowed to get too bad.

If really not the vari-speed, then it could have something to do with
the alignment
of the clutch part in the driven pulley. But, it still knocks when that
clutch is
disengaged, you say. So, that pretty much leaves the back gear. There
is a shaft
with a sliding pinion that is driven by the large toothed-belt pulley.
It has 2 bearings
on the shaft that need to be checked. Pull off the motor, then remove 3
big nuts
near the top of the main quill housing. You can now lift the entire pulley
housing straight up off the spindle. Then, remove a bunch of socket
head screws and
the pulley housing splits in half. There is a plate on the bottom half
with about
6 screws in it. remove these screws, and you can lift the whole plate
out and
expose the backgear section. the two small bearings on the pinion shaft are
cheap motor-type bearings. mine made no noise but I opened it up when I got
my used machine and they were massively trashed, with the ball retainers
smashed
and the shields busted off! Glad I looked!

Jon