Can't disassemble drill chuck

I tried again this evening. This time for the win. Photo shows my setup of a large C-clamp, from an car/truck ball joint service tool kit (Astro 7865) and one of the cup adaptors. That clamp is BEEFY. Ignore the mess in the background. I clamped the clamp to my Workmate, sat on it, and used my favorite 1/2" ratchet (18" long). It took considerable force, but slowly pressed out. Second photo shows that the threaded ring doesn't cover the full circumference, which explains some of the dead space in collar rotation.

Hi MikeK, I don't understand your statement about your second photo.

Regards Nick.

So just needed a lot of persuasion or a really large shock blow to take apart. Was there any damage to the parts at all? I guess a clean and a re lube and good for many more years to come.

My thinking on the split nut was that the gap between the halves allows them to move before pressing against each other which would show up as dead space in rotating the collar. I could be wrong.

Re: the clamp: An online force calculator estimates the forcing screw was pressing 9,000 lbs of force. About 100 ft-lbs on the 18" ratchet and screw is 1". No wonder my little arbor press couldn't do the job.

What's the suggested lube inside the chuck? Light coat of gray German CV axle grease with Moly okay?

Hi MikeK, every chuck that I've ever taken apart has a small gap between the two halves and seeing the how the tube which is used to open and close the jaws is a press fit onto the two halves of the split nut, I can't see how they can move and if they did, you wouldn't have had the problem of getting the tube off, unless they have worn a groove in the inside of the tube and I dare say the gap is probably reduced, or maybe even closed altogether once assembled. I only use some slide way oil on the parts before reassembly, grease has a tendency to dry out and gum up, but the choice is yours.

Regards Nick.

That split collar - which is the nut - doesn't have any gaps in it once it is inside the outer body. Fairly obviously it is an interference fit inside the outer sleeve.

There are two radial grooves in the outer surface of the nut, these are stress raisers so the nut is broken int two along these lines, leaving a unique rough surface at the interface between the two halves which keys the two parts together.

The drive from the chuck key to the two halves of the nut is only by the friction of the interference fit of the outer over the split nut. That's why its jolly tight!

Put it all back together this evening. Sorry, I didn't take photos. I cleaned up everything with acetone - outside, on this fine 42F day - after scraping the original grease out with toothpicks. It was like tar! And had accumulated between the jaws, just where it would be no use.

Minimal wear on the jaw and split nut threads. The parts of the jaws that contact the drill bits were as good as new. Lubed everything and now it operates like butter! It wasn't even this good when new. I'll have to do the drill press chuck now. And maybe all my hand drill chucks. I definitely won't wait another 15 years before the next service.

(Yeah, my thinking above on the split nut was silly.)

Hi MikeK, good to hear you've got it sorted.

Regards Nick.