Re: Bridgeport 2J-2 Head Noise

Jon, I called it a resonance because the sound doesn't exist at low
speeds and seems to build up as the speed is increased and then
decreases slightly at very high speeds. It is a clanking sound. The
back gear seems to be tight with no play and I don't hear any noise
when turning the motor pulley manually. I do recall hearing the noise
as the motor slows down, so this seems indicative of the variable
speed mechanism. I'll have to check this again.

When I changed the three upper head bearings, after getting the
machine, I inspected the plastic bushings you speak of. They were
rather thin, but seemed to be fairly snug to the shafts. I figured
they were thin to begin with. Is this not the case?

The upper housing on the CNC mills seems a little harder to remove
than you describe. I don't see any way to pull the whole thing off.
It looks like it has to be disassembled a layer at a time. I already
had it torn down to the top of the gear box to replace the three
upper head bearings and it wasn't fun.

~petev

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:
>
>
> 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