This is a complicated subject all right. First of all chatter will leave marks that can be seen and felt and are from a variety of causes, but often are not the fault of the machine. Chatter is beyond the scope of what I can do for you, but machining forums like hobby-machinist.com have people who can help if you post pictures of what you're getting.


If you're getting marks that are more subtle in nature (seen but hardly felt), there could be mechanical reasons for it. 

You often will hear single phase motors being blamed, and that can be part of it. 


Things to check or try:

  • It is very important to make sure the lathe is on a solid footing and is not able to rock or vibrate as it's running. Using a heavier base, or anchoring the base to the floor can also help by adding mass to the system and changing the frequency it resonates at.
  • Change gears can also cause this if they are too tight or have other issues. First loosen the bar that the gears are on and swivel it away from the spindle drive gear and see if that makes any difference. If it does, the gears may be meshed too tightly together. Use one or two thickness of paper in between the gears to set the approximate distance, then roll it out from in between the gears.
  • Rubber mounts for the motor will do a lot to remove motor vibration. Since they change the distance of the motor from the motor mount, the tension setting will need to be adjusted, and possibly even a longer belt. 
  • The belt or belts can be an issue as well. V belts have a seam where the belt is a little thicker, and this can cause a vibration. If the lathe is in a cold area, the belt can even take a set like a car tire that's been sitting and will need to warm up to become flexible again.
  • If there are two belts, clocking them in different positions relative to each other could help to reduce the resonance. 
  • Link belts are also known to be excellent at reducing vibration. These are sold by many companies, but searching for the term "link belt" will turn them up. These are belts made up of many small links that can be disconnected and reconnected to make custom lengths.