Vibration in my PM 3520B

I've had my (used) PM 3520B for about 4 months and noticed today that there's a distinct and significant vibration right at 1200 rpm. I did as much troubleshooting as I can and it seems to be in the spindle itself - no vibration from the motor with the drive belt disconnected. Doesn't seem to be noticeable over 1800 rpm or so. Initially thought it was the new jaws on my chuck, but the vibration is present with nothing mounted to the spindle.

The lathe likely has had this issue since I got it, but I only noticed today because my new led lamp that is mounted via magnet to the headstock started to vibrate significantly at 1200 rpm.

The effect of the vibration is noticeable - I was turning a lid for the cremation urn I'm working on, and I ended up with a (kind of cool looking) "chatter" pattern from the spindle gouge - noticeable in the attached photo as a spiral pattern.

Any suggestions as to how if might further diagnose and correct this issue would be appreciated.

If the lathe has adjustable feet you could try screwing one in or out slightly with the lathe running to see how it affects the vibration. Usually the front foot on the tailstock end is the easiest one to work with. It could be that one of the feet is not doing its "share" of carrying the load and you are hitting a harmonic frequency at that rpm.

Good Luck!
Bob

Running it with nothing on the lathe would be one way. Also, like Bob said, one leg/foot might not be resting flat on the floor. Other than that, some times if my headstock is not locked down tight that can make things bumpy, same with the tailstock. The pulley wheels on the spindle drive do tend to work loose, and that generally makes for a 'ticking' type sound, but not run out or vibration. Worst case would be that the bearings are going.

robo hippy

try to recreate the vibration with a small item or spindle, then gradually turn up the speed without the lathe walking, if vibration goes away at higher speed, I believe harmonic was mentioned in an earlier post and that is what it is

if the lathe starts to walk, discontinue and do not repeat

Quote:

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Originally Posted by Reed Gray

Other than that, some times if my headstock is not locked down tight that can make things bumpy, same with the tailstock.
robo hippy

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+1
I had my headstock unlock once and lots of weird vibrations. Also check the pulleys are tight and aligned.

Looks like I just needed to re-adjust the feet. Could be that I never really leveled the bed when I first set it up after bringing it home a few months ago. The feet all seemed fairly tight, but it was out of level by 1/4 bubble or so.

After leveling and locking the feet, the vibration is essentially gone - there's still some roughness at around 1000 rpm but nothing like I had before. I was able to clean up the chatter pattern on the piece I was working on before.

Thanks for all the suggestions. Glad it turned out to be so simple!

Glad you got it fixed. I have a new net of jaws that seem to be introducing some vibration, and I bought them specifically for holding finials. Think I'll try some of the new pen blank jaws...

Lyle Jameison has a video on lathe setup where he discusses this. Adjust the foot while a piece is turning and you can 'tune' out the vibration, or most of it. When all four feet have the same weight on them, the vibration should be gone. You only need adjust ONE foot. This of course assumes the 'load' is balanced and there is no mechanical problem with the lathe.

Thanks, Thom - found the video and watched it, pretty basic stuff but something I hadn't thought about before. I may go back and see if there's any more tweaking I can do to further reduce what little vibration is still there.

Since the 3520 is a cast iron machine, the adjustments of the feet are critical. You can actually, misalign or realign the tailstock live center to a centered point mounted in the head stock merely by adjusting the feet. My floor is not perfectly level. I don't think any poured cement is perfect. I remember the first off balance piece that caused the machine to dance a bit. I had to re-level to get the points back in alignment. After that I bolted it down.
faust