I have a Delta 14-650 hollow chisel mortiser that has quite a bit of runout in the jaws (i.e., using different bits to measure it), but nearly none in the shaft or chuck body. I’d like to remove it to investigate but can’t figure out how. The manual says to put a screwdriver in the top part of the shaft above the motor, and to use the chuck key to unscrew it. But I’m not sure what the last part means—to use the key to hold the chuck so the shaft can be unscrewed, or twist the key as if you are loosening the jaws until the chuck body unscrews. I’ve tried each gently with no luck, and don’t want to break anything. Any ideas?