My lathe is only about 3 or 4 weeks old. It's a Jet 1642, 1.5hp version. When I turn it on, it makes a distinct grinding or clicking sound from within the headstock, once per revolution. I've read about a lot of people having this problem, but all the issues they identified don't seem to be my problem.
Here's what I have done: Opened up the little door where you move the belt, and I inspected where the magnetic tachometer sensor is, and verified that there is nothing rubbing there. Then I looked where the spindle lock button goes into the spindle, nothing is rubbing there. I checked the set screws on all the pulleys, on both the pulley on the motor and the two pulleys on the drive spindle itself. All set screws were nice and tight. Then, just for fun, I took the belt off of the motor pulley altogether, and spun that one by hand, no noise at all from the motor shaft or pulley. Then, with the belt still off (just dangling from the spindle pulleys), I manually rotated the lathe spindle. I heard no noise there either - very smooth.
All this kinda makes me think the sound is coming from the belt rubbing against the side of the pulley in some section as it rotates around, or something like that. I don't really see any anomalies on the belt as I inspect it - nothing sticking out the side that might rub or anything like that. Good news is, I think, if it's just a belt rubbing on the pulley, it's probably not a big deal, just kinda annoying.
Anything else I should check?