Old Union 4” 3 jaw disassembly

[JRT]

I can’t figure out how to get this chuck apart. All the screws are out and jaws as well. You can see the seam down the center. I watched a helpful video of the same one (but larger) being disassembled and he used a rubber mallet. That’s not working for me. Any suggestions? Thanks! -John

 

[benmychree]

Insert the chuck wrench in the receptacles and bump it with a soft hammer alternately, that should widen the split so that it can be carefully pried apart.

 

[JRT]

Great idea! I’ll give it a try. Thank you.

 

[great white]

Looks similar:

I wouldn’t rap on those scrolls very hard. If its like most of the chucks I’ve had apart, they’re mostly cast…or the scrolls bear on cast parts inside.

 

[benmychree]

Looks similar:

I wouldn’t rap on those scrolls very hard. If its like most of the chucks I’ve had apart, they’re mostly cast…

I have had a lot of chucks apart, never saw one with a cast scroll, all have been hardened steel. Also if the bolts are long enough you can back them out partially and rap on them or find longer bolts and do the same.

 

[JRT]

Looks similar:

I wouldn’t rap on those scrolls very hard. If its like most of the chucks I’ve had apart, they’re mostly cast…

Thanks!

 

[JRT]

Got it! I made a little brass piece to rap on and then used it as a wedge until it finally came apart. Any reason I can’t clean with 90% isopropyl and the oil really good?

 

[benmychree]

Got it! I made a little brass piece to rap on and then used it as a wedge until it finally came apart. Any reason I can’t clean with 90% isopropyl and the oil really good?

I don't know if alcohol will cut grease, I'd just use paint thinner or mineral spirits.

 

[great white]

I prefer varsol for degreasing myself. 90% ipa is 10% water. The ipa will flash off, but the water will not. That will take much longer. Water can make rust and I’d rather not take that risk in finely machined internal parts…

 

[JRT]

Paint thinner would be good and not start rust like 90% ISP? I can’t get Mineral Spirits where I live, unfortunately.

What about denatured alcohol or acetone?