The threads are most likely burred from the set screw. Work the Quill nose back and forth a little. Be careful not to bugger the quill threads(ID). They will be hard to straighten out. The nose cap not so difficult.
Find a brass tipped screw to replace it with to reassemble. Or make a brass disc to fit the screw hole so the brass clamps the threads.
Some quill caps have threaded holes on the 'face' for attatchments or something. You might be able to use them to turn the cap. Or drill corresponding holes in scrap plate to match the spaner holes, if that fits your application
Last edited by krutch; 07-07-2012 at 02:15 PM.
Mentally confused and prone to wandering!