Cracked my Jacob's chuck sleeve tonight...

[n9viw]

Well, it started well.

I picked up an old Jacobs model 34 chuck with JT6-MT2 arbor on ebay, but it was stuck. Liberal amounts of PB Blaster got it free from the stuck position to wide open, but it wouldn't close past that original stuck position. Watched a bunch of YT videos on rebuilding a Jacobs chuck... that's EASY! Even a monkey like me could do it.

Brought it to work, knocked the chuck off the arbor easily enough. Put the chuck in the hydraulic press and made sure the jaws were back behind the nose, and it came out easy as you please.

On the bench, made sure I marked the jaws and body locations, got the half nuts off and pried the jaws out. Bunch of rust on the jaws and in the jaw bores, keeping them from closing. Cleaned that all off, degreased, deburred, wire wheeled, greased up, got the jaws in and the half nuts set and flush. Easy!

Put it back in the press and got it just past halfway, and with very little warning, BANG. Looked at the sleeve, and ain't that nice, a nice bright lightning bolt of a crack from stem to stern. Cue loud cussing.

Turns out, when reinstalling the sleeve, MAKE SURE THE TIPS OF THE JAWS ARE EVEN WITH THE NOSE OF THE CHUCK. I had mine all the way back, and as it turns out, they can go back further without the sleeve than with it. As a result, the sleeve caught on the end threads of the jaws, and the resulting ramp just split that sleeve like a wedge through a log.

So now I'm going to try welding it, but I worry about distortion. Replacement sleeves are available, but are almost as much as a new chuck. All for a moment's missed detail. Don't let it happen to you.

 

[SWIGIN]

The price of a new sleeve isn't that bad at $47 at Mcmaster Carr.

 

[Eddyde]

Same thing happened to me a while back. I never knew exactly why it broke, I just figured the sleeve had a flaw in it. Now I know, it was the error of my ways...

 

[cathead]

I might have one for you. A photo would help and I will have a look see.

 

[n9viw]

The price of a new sleeve isn't that bad at $47 at Mcmaster Carr.

Saw that, they're the cheapest I've found. A bite in the butt, because I only paid $25 for the chuck and arbor. Up til then, I thought I had a heck of a deal. <facepalm>

 

[n9viw]

I might have one for you. A photo would help and I will have a look see.

I can't weld for beans. Supposedly that's MIG. Most of it piled up on top, and when I ground it flush and reinstalled it, it cracked again. One of our pipefitters is here today, he's good at sanitary welding too, so I'll just give it to him and owe him a beer after work.

 

[n9viw]

Thank God for people who know how to weld. Clamped the tail of the arbor in a vise, put a drill in the chuck, and reefed on it, no slippage. That's $50 saved! I owe that guy more than just a beer. Very pretty work.

 

[n9viw]

By the way, the cut above the weld isn't a widening of the crack, it's the vee relief he buzzed in over the crack with a thin blade in a die grinder to give him more penetration. He said he didn't continue the weld into the teeth because he didn't want to have to try to grind that out.