Look for the source of vibration:
- Does the motor vibrate when run without a belt? If so, faulty motor, perhaps a shorted winding. Also ensure the shaft turns without wobbling – might be bent. Replace the motor if it vibrates badly.
- Again without the belt, turn the lathe over by hand feeling for binding. If found, look for the cause – gears too close together (easy adjust – should be apart by the thickness of a sheet of paper, maybe doubled). Or might be something nasty like a worn or bent spindle or knackered bearings.
- Put the belts back on and check they are aligned. (See below)
- Take the chuck off and run the lathe. If the vibration stops, check the chuck for balance and that it’s correctly attached to the spindle. (Worn thread, cross-threaded, dinged register etc.) Dud chuck is unlikely to cause vibration unless a jaw is missing, or they’re wildly off centre.
- Does anything wobble visibly when the lathe is spinning?
- Might be possible to identify the source by listening. Ideally with a stethoscope, but a wooden rod works too. Be careful not to get hair, rings, or clothing caught in a running lathe. Think scalping, fingers ripped off, and face pulled into steel gears.
- Run the lathe with the leadscrew disengaged. If the vibration stops, inspect the leadscrew – they are easily bent. If so, take it off and straighten it. (Ask if necessary.)
- Worn spindle bearings. With power disconnected put a 300mm length of 25mm diameter pipe in the chuck as a lever. Waggle it up/down, side to side and fore-and-aft. Chuck and spindle shouldn’t move in those directions, only rotate. Severe wear might be visible, but best measured with a DTI.
Alignments. Can’t tell from the photo of the new arrangement, but the original layout looks off. The pulleys have to be aligned at right angles and the motor looks off. The red line suggests the motor and intermediate pulley are misaligned: the motor is a bit off, fore-and-aft and not at a right angle.

The green line between the intermediate shaft and the lathe pulley look reasonable, but cameras can distort reality. Check the equivalent alignments in the new build with a straight-edge and square. With luck the vibration is due to misaligned pulleys because the fix is just an adjustment, no need to replace faulty parts.
Good luck,
Dave