I have 2 Chinese 1/2 inch drill chucks, one for my LMS Mini Mill & the other for my drill press which is also Chinese. Both are marked "JT 33" which I understand is the drive taper. My problem is that the drill press chuck key slips when I try to tighten it securely (when using larger drills.) I bought a new #3 Jacobs key which seems to fit OK but it still slips. I tried the nearly new key for my import Mini Mill chuck & it's no tighter. Am I correct in assuming that my d/p chuck gear's the problem? Thanks!