Problem Rebuilding Jacobs Chuck - Suggestions?

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bfd said:
so at .oo05" I would polish the bad jaw until it just fits might only take .00025 to get it to fit and at that number runout will be minimal at best. at least you will have a chuck to use with no additional cost. you might have got a hole at the very least of its tolerance and a jaw at the very most of its could happen. I repeat polish it until it just fits bill
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4gsr said:
]Sometimes, the jaw will go in if turned 90 degrees from normal and go in. If you can get it to do just that, twist the jaw several times to get a dull spot in the ID of the chuck body. This would indicate positive metal that needs to be removed. Now it the jaw will not go at all turned 90 degree, then it could be the jaw. I have polished the jaws too to get them to go in.
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I decided to take the advice on polishing. Taking my time, I slid the jaw into the bore and looked for the worn spots when it was pulled out. I started with 400 grit emery paper and finished with 1500,
which gave a better surface finish than the parts had when received. I just kept working at it a little at a time, until the jaw slid in normally. I really didn't take much material off: the jaws are pretty
hard, and when I measured it had barely changed from measurement taken last week. Assembled it with some chuck grease, it works just fine.

I did go back and measure the parts that came out when I took it apart. They measured up exactly the same as the #1 and #3 jaws. I think that #2 jaw was a bit out of tolerance from Jacobs,
but it's all good now.

Thanks to everyone for your suggestions.
 
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That's great. At least you have a working Chuck. Let us know how it drills and if you check TIR using a 1/2" dowel pin/Indicator,
please let us know how much run out the chuck has.
 
I measured the run out at .004 - .005". Not great, but I have a 4 jaw chuck if I need better.
 
.004-.005" TIR is actually not that bad considering the jaw problem. The spec for that Jacobs is around .005" TIR.
So you did ok. The Jacobs super chuck spec is .004" TIR, You got Jacobs Super Ball Bearing chuck TIR with a plain bearing chuck!
 
I'm having a problem rebuilding my 16n superchuck, Jacobs wants $285 for the kit
20n $598 for the kit. It's just a few parts. :mad:
 
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Rebuild kits for 16n and 20n come up on Ebay, sometimes. Do you have a Hartford, CT USA 16n or the new?
I bought a 14n rebuild kit on Ebay, NOS for $30, complete with bearing balls. I would follow search on Ebay and get email updates.
I've never seen the new Import kits on Ebay.
Msc has the 16n kit for $130. All of these new rebuild kits are for the new Import Jacobs.
https://www.mscdirect.com/product/details/08595167
 
dlane said:
I'm having a problem rebuilding my 16n superchuck, Jacobs wants $285 for the kit
20n $598 for the kit. It's just a few parts. :mad:
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Dlane,

I may have an extra 20N jaw kit that I'll sell you if you're interested. I promise not to charge over $498 for it. :grin:
PM me if your interested.

Ken
 
First you need to know if his Jacobs are service kit models, new import or USA Hartford CT. chucks.
Jacobs changed the race design for the newer chucks. They are not inter-changeable.
 
EmilioG said:
First you need to know if his Jacobs are service kit models, new import or USA Hartford CT. chucks.
Jacobs changed the race design for the newer chucks. They are not inter-changeable.
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The kits I have are for the older chucks. The difference is like you said is the nut and bearings used. Now, you can use the same jaws from the old to the new, at least, the 16N will let you do it. I've done so on one of the rebuilds in the past. Ken
 
For those that have not encountered a newer Jacobs ball bearing chuck. The older ones have loose steel balls that have to be loaded one at a time. And you generally loose one or two in the process of assembly. Don't worry, if you loose a few, its not the end of the World, it will work fine with the missing steel balls.
The newer chucks has a plastic retainer that the steel balls are loaded into at the factory, that keeps you from loosing them. Also, the steel balls are a little smaller in diameter. And there are some other differences in the chuck body and sleeve. But appears the jaws themselves did not change, at least in the 16N chuck. Ken
 
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