tesla893/printrbot-variant — comment on commit b82d197cce4ee47e5e6b6fc69a438dc51508913f
File:  line 0
By whosawhatsis:

I really don't think spinning the pulley while pressing it against the side of a screw is a good idea. First, you have to have the screws loose enough to allow it to spin but tight enough to keep the pulley from moving around (you'll need a locking nut on each side). Second, turning against the screw will push the pulley along the threads until it presses against the nut on one end (increasing friction). Third, once it is pushed all the way against the nut and can't move further, the shaft of the screw will basically turn into a router bit, grinding the bore of the pulley and generating even more friction. Friction generates heat, and it doesn't take much heat to soften PLA. With the pulley likely going back and forth tens or hundreds of thousands of times in a print, I don't thing the pulley would last long.