I have a craftsman router mounted under my router table. I have had it in service ~ 3 yrs. I recently wanted to change from 0.25″ to 0.5″ collet (for the 1st time). The collet is held in place by a small screw. It’s a ccw thread and the screw head was plugged with sawdust, etc. Got that all cleaned out, but (of course) I couldn’t budge the screw. I tried a penetrating oil to no avail. Any suggestions would be appreciated.