DIYbanter - View Single Post - Bridgeport Mill Making Knocking Or Clicking Noise

Jon Elson[_3_]

wrote:

On Saturday, March 18, 2017 at 12:51:08 AM UTC-4, wrote:
A friend of mine has a Bridgeport knee mill making a loud clicking or
knocking sound in the head. I could not find any obvious reason. So I
sorta just said sorry man I can't find anything. Well about 2 weeks later
Karma I guess, I have a large Jet knee mill 3 phase started doing the
exact same thing.So I am telling myself the same thing, (sorry man can't
find anything ). Has anybody got info as to a guess what it is ? I am not
a machinist just a hobbiest. Thanks for any input you might offer.

It is not a Varispeed.
Oh, well, that BLOWS that theory! So, this is a 1J (4 step pulley)?
There is a 1" belt that is the first stage of the back gear reduction.
The belt is held on one of the pulleys by a flange that is bolted to the
face of the pulley. That could be working loose, or the belt could be
disintegrating. Take a look at that assembly, rotating by hand and looking
with a flashlight.

Disengage the feed worm (little crank on right front of head).
Put the direct-drive clutch in neutral (push lever on top clockwise looking
down from top, it raises the driven pulley about 1/2") and spin the spindle
as fast as you can. Does it still knock? If so, bad news, that sounds like
main bearings.

Doesn't knock? There are a bunch of commodity bearings in the head, in the
back gear assembly. First, remove motor (it's heavy). Then, remove nuts
under belt housing, and you can lift that straight up and off the spindle
spline. The back gear is under a metal cover with a few screws. If the
bearings are blitzed, the ball retainers will have crumpled up and been spat
out. That's how mine were. Also, the motor bearings could be bad. Thay
are relatively easy to replace.

I can't say if your Jet is built the same way, but it probably is fairly
close.

Jon