Most expensive part of a Shopsmith is the headstock. Consist of motor, speed control and spindle assembly. A replacement goes for about $1,300.00. The motor should start w/o hesitation, the speed changer should go through the range smoothly and not bind anywhere through the range. Shouldn't be any noise from the spindle except a whirring sound. No wobble at the shaft end, and extend full range smoothly as well. Mount a chuck on the shaft and spin a long bit. If the shaft is bent, the bit will show it up.