I've been doing a fair bit of drilling on the lathe lately and have run into some issues with the tailstock. Tonight I figured out what the issue is. When drilling the quill wants to turn in the tailstock but that is prevented by the set screw that rides in a slot cut into the top of the quill. However when using larger size drill bits, like 1/2" and bigger, there is a lot of torque and that causes the sides of the quill groove to distort where it contacts the set screw. Then it becomes...
Tailstock Quill Distortion
Tailstock Quill Distortion