[Source] 6j 6 Inch Set Thru Chuck Repair

Bamban

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A year or so I thought made a great buy when I bought an older Buck 6J 6 inch set thru chuck. It sat for a long time before I could swing the cost of a D 1-4 backplate. When I finally got around checking out the lathe I found out why the previous owner sold it.

The jaw lift up when i grab and tug in the dialed in test bar. 8 called a couple of commercial operations in OH specializing on chuck repair, one flat out said non repairable when I described the problem. One asked to send it for evaluation. Today I got confirmation that the jaws are indeed lifting and there is nothing they can do but sell me a new chuck.

I already have close to 600 on both the plate and chuck, I could not stand the thought of buying a new chuck.

Question.

Is there anyone here who has successfully repaired worn out chuck jaws or the T slots the jaws slide on? If you have done one, have the tools to do the repair, and have the time to do the job, and willing to do it for a fee, please let me know.

Thank you.
 
You could make a complete new chuck body out of a piece of ductile iron from Dura Bar.

I have a rainy day project I've been carrying around with me for the past 15 years to build a new 4-jaw chuck body for a set of jaws I have from a Cushman chuck that was trashed out.
 
You could make a complete new chuck body out of a piece of ductile iron from Dura Bar.

I have a rainy day project I've been carrying around with me for the past 15 years to build a new 4-jaw chuck body for a set of jaws I have from a Cushman chuck that was trashed out.

Thank you.

Making a new body is way above my pay grade, skippper. I am still on my crawl phase in this machining journey. I've chambered close to a couple dozen barrels from blanks, but that is kid's play for most of the people in this forum.
 
I'm guessing the wear's in the jaw slots of the body, not the jaws... All I can think of is re-cutting the slots, adding back some metal once they're true - silver-solder shims to take up the play on the worn (but now re-cut) faces? Do you have a mill and infinite patience?

Dave H. (the other one)
 
I'm guessing the wear's in the jaw slots of the body, not the jaws... All I can think of is re-cutting the slots, adding back some metal once they're true - silver-solder shims to take up the play on the worn (but now re-cut) faces? Do you have a mill and infinite patience?

Dave H. (the other one)

Dave,

I have a BP and have patience, skills is work in progress. I can get the correct T slot cutter, I suppose this is what I need to recut the slots for the addition of shims.
 
I'd first check the slots in the jaws, e.g. gauge block and feeler gauges, depth mic', to be sure they're still straight and parallel in themselves and relative to the back of the jaw where it bears on the front of the chuck, but my money is on the chuck body slots...
Usually there's a "key" (actually part of the body "left behind" when the body's machined from a casting) each side of the jaw that hold it parallel and at the right distance from the scroll, I suspect (not having seen your chuck) that this is the crucial fit: what's going to be necessary is either machining true and brazing/silver-soldering shims to make it up to the correct dimension *and parallelism* relative to the chuck face, or (possibly a simpler job?) machining off the existing key and cutting a slot (also parallel and at the right distance!) the width of the original key and then inletting a key to fit the slots in the jaws. This could be something like gauge plate, bronze, ideally you don't want the same hardness as the jaws as that can lead to galling.

Bear in mind I've not had to do this myself, but it's what I'd do in the circumstances (although I'd probably put in more hours than economic, I would rather fix something than buy a new one...)

Here's a couple of quick Crap-O-CADs of the stages, Original - halfway - fixed, of how I'd go about it (I think!) depending on where the original keys are on your chuck - Excuse the over-simplification!

If the keys are below the chuck face:

Chuck fix.PNG

Or if the keys are flush with/form part of the front
Chuck fix 2.PNG

Dave H. (the other one)
 
Dave,

You could key the chuck as you show. The old BSA chucks are built that way. But on a 6" 6-jaw Buck chuck, there is no room for keying when you get the inner diameter of the chuck. The jaw slots almost intersect each other. Not much meat there.
The other piece of the puzzle that has not even been mentioned is the scroll plate. It's more than likely worn, bad places in the scroll, maybe even some gear teeth missing or damage. Plus the fit of the scroll to the chuck body is probably very sloppy. This doesn't help with sprung jaws. And even if you fix the jaws, the repeatable accuracy of the chuck then depends on the scroll.
So you are back to square one. My original statement of making a new chuck body would be so much easier than making keys and inserting them into a worn chuck body in my opinion. The OP says he's done many of chambering barrels in his past. He can easily build a new chuck body. To me that would be much easier than chambering barrels to me, but I've never done it. I'm sure I can and eventually will try.

Last, it would be much easier to buy a new 6-jaw in the long run. There are a couple on eBay in the 6" OD range that can be had for under $500.

Ken
 
Ken, I did say I'd probably put in more hours than economic...

If costed out at a sensible hourly rate, the replacement chuck would be a bit of a bargain, I suspect.

Dave H. (the other one)
 
Before I sent the chuck to be repaired I took it apart to do visual. Nothing broken, the scroll appeared to be in good shape from what I could tell. I really do not how to inspect one other than looking for gouges or broken pieces. All is intact. The gears are all there and the pinion appears to be in serviceable condition. When I get the chuck back from the repair place I will post some pictures.

A new chuck is indeed the easy way out, I am trying salvage a bad investment.

Gents, thank you for the information. I will definitely tackle the repair and will be howling out for help when the time comes.

Advice/suggestion are welcome.
 
.....snip.....Advice/suggestion are welcome.
Put the jaw set up for sale, for the price you bought the chuck for. Be sure to give dimensions for the tee slot as well as basic overall dimensions of the jaws. This will help on selling the jaws. The adapter plate, save it for future use.
 
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