On Tue, 05 Jun 2007 12:55:42 -0700, 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.
Please, if anyone knows whats going on, let me know. Thanks

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.