vibration problem

wrote: Hi, I have a delta 14" variable speed lathe. There is a certain range of speed (about 1/3 of the total range) where the lathe starts to vibrate and wobble out of control, and it seems to be getting worse. (clip) ^^^^^^^^^^^^^^^^^ Certainly you would not ask this question if the vibration were coming from an out-of-balance piece of wood. It happens even when there is nothing attached to the spindle, right?

Take off the belt and run the motor. Probably not caused by the motor, but best to check things in order. Inspect the belt--is it about to break? Check for anything loose in the spindle/headstock stuff. That's all there is.

Everything has a natural frequency of vibration (cars, washing machines, bridges, even trees). If you match the frequency, or a multiple of it, to the object, it will vibrate. A variable speed motor is very helpful here because you can tweak the speed a little so it won't vibrate so much. Add a lower shelf to your lathe and put some sand bags on it. Add the extra weight will change the natural frequency of your lathe, plus absorb some of the vibrations.

A couple possibilities to look at:

1. The belt gets loose at certain speeds with a Reeves drive. You may see it "bellying" out.
2. Also, the sliding pulley can wear on that lathe. Then that injects vibration. Having the bearings at 4" apart or less with the pulleys hanging way out (relative to the bearing c-c length) magnifies any drive issues.

You can also find that the vibration is caused by taking too big a 'bite' of the wood. I have a Vicmarc 100 which is a fantastic lathe but I still get the vibration from time to time. I then realised that it was me taking too thick a cut and now I use the vibration to tell me that it's time to take a finer cut.

Kindest regards

Paul