VMC spindle noise question..

No. 40 size, turn by hand and hear a faint "scrape" noise with each revolution....350 degrees of dead silence and 10 degrees of scrape noise. The noise is louder when listening from above, so it is probably belt or pulley related. The cog belt looks perfect however. The question is, is it even possible it would be spindle bearing related ? Seems like any spindle bearing issue would result in a continuous noise or rumble....but I'm not 100 percent sure of that, thus this question.

FWIW, noise is the same with or without a tool in the spindle. When running under power, the scrape noise is audible only at really slow RPM's.... at about 400 rpm can no longer hear it. But suspect it is still there even at faster speeds as the spindle is not quite as quiet as a sistership I have.

Did the machine sit for a while? Someone told me not too long ago about belts getting a flat on them from sitting idle for a length of time.
Can you pull the belt and give her a turn?

Does it have through spindle coolant? I have seen the TSC coupling start going bad and do that.

The most popular items in machining, are chips. Sum of them get stuck, maybe in a place it can't get out of.

I think I'd step off that curb, before I'd get too Hi Fi about anything else.

Just guessing...

Regards,

Stan-

I like the TSC coupling idea, I have a had a myriad of problems with mine in the and future.

It has gotten to the point where I keep one in my spares stock.

Has the machine been sitting? Iron pulleys rust like no tomorrow. Usually half the pulley will rust, the half not covered by the belt. Let the spindle run all day and see if it cleans up. Otherwise, loosen the belt and see if the noise goes away.

Also, check the spindle encoder belt if it has one. Those can get noisy too.

No spindle encoder, no TSC....encoder on rear of spindle motor same as axis motors. I haven't taken anything apart yet but noticed the scrape sound can not be heard in reverse.. unless I use a bearing stethoscope... i.e. without stethoscope, no noise at all in reverse...but with stethoscope can barely hear it. Much louder in forward. Also much louder at the top of the quill near belt pulley.

Fixed it !

Moved the spindle motor forward some to loosen the cog belt...the looser the belt got the more quiet the noise got...but still detectible with the stethoscope. So, unbolted the motor, tipped it back, belt now free. Spin spindle by hand...absolute silence...excellent ! Turn on spindle motor..quiet whirr as it should be....excellent ! Examine both pulleys...no rust, no chips...look good. Examine belt...looks fine.... WTF ??

But then I felt the belt as I threaded it thru my fingers.... to my surprise I found two places where the belt had tiny cuts on the top...cuts so small and at such an angle as to be impossible to see from above. A bit of the wire core was coming out those little cuts as well. Took some small wire cutters and trimmed those areas up, put it back together and damned if that wasn't it...spindle is as quiet as a church mouse now.... EXCELLENT !

Another interesting tidbit is I now know why it was noisier in forward than reverse. The two cuts were sliced at an angle such that they would tend to make more noise one direction than the other. Maybe that is key to knowing the problem has to be a belt since I doubt a worn bearing or rusted pulley would ever sound much different one direction or the other. Anyhoo, that's todays repair from Dogpatch, SC folks....time for a victory beer.

Milacron