The "set screw" is not really a set screw, but an anti-rotational locating pin (w/threads.) Remove the pin completely and if you can tighten the locking knob enough to keep it tight, the toothed clutch washer is rotated to the "wrong" position. With the pin in, it stops the rotation of the locking knob so you can't overtighten it, and it won't come off completely when loose. In it's proper position (clutch washer) you'll have longer turn tightening the knob, and a short turn to loosen. Installed wrong the turn to tighten is short, with a long turn when loosening before it hits the stop. It's not getting tight enough when against the stop to overcome the intertia from starting and stopping. Teeth out- no grease on clutch washer, however the grease won't stop it from functioning properly- it just messy.
BTW- I just sold a 1514 (in cabinet) at an auction for $170. You done good on yours.
Last edited by oldmanquilts; 02-01-2020 at 04:34 PM.