T 18 +3 E Chuck Stuck in fully open position

[JamesW]

So, as the title says my drill chuck is in the fully open position. I've tried WD-40 and tapping (and am happy to try again), but when I try to twist it, it just slips over to the locked position without the chuck jaws moving. Is there a trick I'm not aware of to disable the chuck lock so I can apply some torque?

 

[JamesW]

I got it! The small strip just behind the part of the chuck that loosens and tightens the jaws now has some vise grip marks, but it is turning freely again.