if we are talking boat a traditional chuck, and not an insert bit variety of, then allow me to tell my tale. My trusty R86116 in hand, a few days ago, 07/03/24, I finally freed my bit holder from its bond. What it took was heat, Gunk's Liquor Wrench, a shop vise mounted to its bench. and a dollop of fortitude, and a belief that this could work.
1st was finding all these things: Then liberal dose of Gunk's, around the tip, front and back, and all around. Tap w/hammer to produce micro chasms to allow
in all this lube.
2nd After sitting for 30 min, apply the heat from the heat gun recently reunited with owner, front to back, etc.
3rd Driver could be in vice already, but if not, in it goes with the chuck fitting snuggling in its jaws.
4th Snug up the driver in more, since we do not want the driver shift around, set the direction of driver to reverse
5th Apply bursts of power. Never mind the god-awful noises, but make sure the chuck is not moving. Apply power a sec or so per attempt.
6th Retrieve bit that fell from driver, and give yerself pat on the back.ec
Please note that securing the bit holder in the vise, and not the chuck, will only make the jaws of chuck tighter