Pratt and Burnurd 4 Jaw - keep or sell

[Dabbler]

awww, gosh darn. I'm looking for a 4J chuck that is small. (all mine are over 8")

really just kidding.

I will be sourcing one locally to grip small parts in my big machines. There is a nice 10" PB 3 jaw scroll chuck near me for only 400$. Very tempting! - Mine is a 12"

 

[talvare]

So the likely hood is that if the jaws wear out the chuck becomes useless?

Not necessarily. One of the more common problems with chuck jaws is what is known as bellmouthing. Many folks, including me, have corrected this problem by grinding the jaws with a tool post grinder or similar set-up. Many times a chuck can be saved from the scrap bin with little expense and not that much work.
Ted

 

[Dabbler]

Even if the jaws slide loosely, a four jaw can be used to do good work. Best if they are a great fit, but they can be rehabbged to an extent, and good technique can make up for a lot.

 

[bollie7]

While not 100% directly related to the OP's question I'd like to relate some info re Pratt Bernard chucks.
First a bit of very relevant background.
A friend of mine has had his own small (as in one man band) commercial machine shop for a number of years. He has a 10 acre property that was out in the sticks when he bought it 40 years ago. That property is no longer in the sticks so he recently sold it for a considerable sum. Bought another smaller property further out in the sticks and is in the process of moving there including his work shop. Hes trying to retire and as hes cashed up, has bought himself a brand new Colchester lathe. (about $55Kaud).
He related this info to me. Apparently Pratt Burnard chucks (Colchester and Pratt Burnard are all part of the same company group - 600 Machinery) are made so well, that parts are interchangeable. So you can take a set of jaws off a new 3 jaw and swap them to another new 3 jaw body and the chuck will run true. I've never heard of that. Most 3 jaws I've ever seen were numbered as were the jaws.
My friend told me that bloke at 600 Machinery demonstrated swapping the jaws and then used a test bar and dial to show. My friend said the needle on the dial didn't even flicker. He was astounded. This was on either a 250mm dia or 300mm dia 3 jaw.
How good is that?
A Pratt 3 jaw that size wouldn't be cheap though I'd think.
Regards Peter

 

[Ben17484]

A 4 jaw like you have (not a scroll) is usually reversible. 3 jaws, though with a scroll are not. They are specific for that chuck, usually in a final grinding.

I’ve just checked, and you’re right. Mine 4 jaw jaws are reverseable. That’s helpful to know.


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[Ben17484]

This is the three jaw P&B I’ve kept as well:

The 4 jaw is in great condition, but this 3 jaw needs a tear down and refurb. The scroll is crunchy and it all could do with a good clean.

On the subject of spare jaws, I got all of these from the seller when I bought my smart and brown lathe with which these chucks came:

I need to have a look through and see which of these fit the two P&B chucks.


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[projectnut]

As a general rule, you're not going to find new jaws for an old chuck. Not to say it doesn't happen, but it is definitely the exception.

I would whole heartedly agree. I bought a 5" Cushman chuck missing the inside jaws from a used equipment dealer over 20 years ago. I went back several times to see if i could find the missing jaws. He has shelves with close to 1,000 sets for various size chucks, but I've yet to find some that fit my Cushman. I've also taken a sample (outside jaw) to half a dozen other equipment dealers to see if they had anything. I'm still looking 20+ years later.

Do jaws generally wear out before the chuck would? I’d guess so. So the likely hood is that if the jaws wear out the chuck becomes useless?


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It's hard to kill a 4-jaw chuck by wearing it out. I needed an 8" 4-jaw chuck for my Seneca Falls lathe in a hurry several years ago. I found a well-worn L W at my favorite equipment dealer for less than $50.00. When I got it home, I realized it had been in a crash and the backplate was cracked in several places. I didn't have time to return it, so I repurposed a spare one I had lying around.

I knew the chuck was worn and the jaws were lose, but needed to use it so once the backplate was finished I put it on the machine. When I started it up the jaws rattled like cassinettes. Even with all that wear I was able to dial in the stock to less than .001". I've used it many times since then primarily because of the way it's built. It has a hollow back making it much lighter than the other 8" chucks. I'd much rather use it on the old plain bearing lathe than a solid chuck that weighs close to 40 lbs.

 

[Dabbler]

that parts are interchangeable

I contacted PB regarding my 3 jaw chuck and they told me all I had to do was order the part# and they'd fit. I don't know any other chuck maufacturer that can claim that. My chuck is over 45 years old. Lucky I found the outside jaws just after. That kind of quality comes with a $$$$ price.

 

[MrWhoopee]

I contacted PB regarding my 3 jaw chuck and they told me all I had to do was order the part# and they'd fit. I don't know any other chuck maufacturer that can claim that. My chuck is over 45 years old. Lucky I found the outside jaws just after. That kind of quality comes with a $$$$ price.

Did you happen to get a quote on those jaws?

 

[Dabbler]

For my 12" scroll chuck, in their 'high precision' line, they were 750$ for a set. More than 20 years ago.