Used Jacobs Rubberflex chuck saga - buyer beware

I recently bought a used Jacobs Rubberflex chuck and collet set, and I wanted to relate what happened. I found a 91-A6 hand wheel chuck that had a 1-1/2 - 8 adapter already on it, just what I wanted for my 10K. However, when I screwed it on the spindle, the runout was about .010" - not good. I had assumed that the adapter would probably need to be machined on my lathe, so I removed the chuck from the adapter and re-machined the taper and mounting flange. Problem was, with the chuck re-mounted on the adapter the runout was still about .004". Took the chuck back off and disassembled it - what a dirty mess. I don't think it had been cleaned since it was new, but at least there was no visible damage, so I cleaned and lubed it, put it back on and - no improvement. Still about .004" out at the taper. I ended up using the toolpost grinder to re-grind the collet taper and got the runout down to near zero, so it turned out OK, but it was more than just runout - the taper was unevenly worn, with a low spot in one place. Moral of the story - if you get a used chuck that was run hard and put away wet like I did, don't be surprised if it doesn't perform well. I'd be up a creek without a paddle if I didn't have a grinder to fix the taper. So if the choice is between a used chuck without a known history and a new one, sometimes it might be a better idea to spend for a new one, unless you have the time and means to fix a worn chuck - it took me most of the day. On the bright side, the chuck is very well made, easy to use and is now very accurate. Anyway, buyer beware.

Did you try to move the chuck with a mallet on the adapter?

Danny VanVoorn said:

Did you try to move the chuck with a mallet on the adapter?

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No - the chuck fits on a taper on the adapter, so you can't move it around, and the threads onto the spindle are similarly non-adjustable. The other problem is that the collet taper was worn unevenly and had to be ground.

Correct me if I am wrong, but that chuck and collet system is not made anymore. If so, then the decision to buy new is mute.

Tom

Blob said:

I recently bought a used Jacobs Rubberflex chuck and collet set, and I wanted to relate what happened. I found a 91-A6 hand wheel chuck that had a 1-1/2 - 8 adapter already on it, just what I wanted for my 10K. However, when I screwed it on the spindle, the runout was about .010" - not good. I had assumed that the adapter would probably need to be machined on my lathe, so I removed the chuck from the adapter and re-machined the taper and mounting flange. Problem was, with the chuck re-mounted on the adapter the runout was still about .004". Took the chuck back off and disassembled it - what a dirty mess. I don't think it had been cleaned since it was new, but at least there was no visible damage, so I cleaned and lubed it, put it back on and - no improvement. Still about .004" out at the taper. I ended up using the toolpost grinder to re-grind the collet taper and got the runout down to near zero, so it turned out OK, but it was more than just runout - the taper was unevenly worn, with a low spot in one place. Moral of the story - if you get a used chuck that was run hard and put away wet like I did, don't be surprised if it doesn't perform well. I'd be up a creek without a paddle if I didn't have a grinder to fix the taper. So if the choice is between a used chuck without a known history and a new one, sometimes it might be a better idea to spend for a new one, unless you have the time and means to fix a worn chuck - it took me most of the day. On the bright side, the chuck is very well made, easy to use and is now very accurate. Anyway, buyer beware.

Click to expand...

Those things have not been made for years, used is your only choice. Why anyone would buy one over a 5c or 2j I have no idea. No new ruberflex collets are available, 5c and 2j are no problem. I own all 3 types so I have a reasonable perspective.

TDegenhart said:

Correct me if I am wrong, but that chuck and collet system is not made anymore. If so, then the decision to buy new is mute.

Tom

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Nope, you're not wrong. My suggestion of used vs new was meant generally, not about the Jacobs. Moonlight's comment is worth paying attention to as well. My desire for the Jacobs chuck is just one of those things. I also have other collet systems, including 5C, ER, etc - can't have too many tools. :-) Sorry if my post was confusing.

Blob said:

I found a 91-A6 hand wheel chuck that had a 1-1/2 - 8 adapter already on it

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Reviving an old thread:

Was the adapter a home brew or were these chucks available with that size thread from Jacobs?

I ended up with a nice set of collets for cheap money and would like to use them on my Atlas 12" (1-1/2" 8TPI thread). But the closest mount I've found is a 2-1/4" 8TPI thread.

Perhaps I can make my own adapter. But is the mount on these chucks removable?

Gary

I have the Model 50 chuck, which is better suited to the 1-1/2" spindle of the 9/10K.
Got it from a retired machinist that had bought inventory from a Rockwell plant when they closed (Rockwell's also had the 1-1/2 spindle). Yeah- condition is everything, no parts are interchangeable or easily fabricated from what I see.

I was assured mine was excellent, and it was. Collets were in great shape as well. The set-tru type adjustment allows dial-in to within a few tenths, even without effing with it, it'll be within a half-thou most of the time. Wide range makes it very easy to use.

No - the chuck fits on a taper on the adapter, so you can't move it around, and the threads onto the spindle are similarly non-adjustable. The other problem is that the collet taper was worn unevenly and had to be ground.

Click to expand...

It is probably best to take you at your word.
However, if the chuck was not perfectly center on the mount, and coaxial, it would exhibit that symptom.
Did you inspect the chuck by other means?

AFAIK Jacobs never made a 1-1/2" 8 mount, so what was provided was almost certainly shop made.

I made one for mine, it is documented on PM somewhere in the past. Mine came out under .001" runout and with a little bumping (as mentioned by another poster) got better. It seems fine today, i have not indicated it recently.

Those things have not been made for years, used is your only choice. Why anyone would buy one over a 5c or 2j I have no idea. No new ruberflex collets are available, 5c and 2j are no problem. I own all 3 types so I have a reasonable perspective.

Click to expand...

These things were not really intended from "small" lathes. However, today, they provide larger capacity than 5c with about 1/2 the overhang, on small spindles. Any 5c add-on chuck for these lathes puts the whole collet length and the backer of the chuck out past the original spindle nose. Diameter practical limit with add-on 5c is about 1-1/8", or only through-the-collet limit of 1" . a 9- series jacobs accepts up to 1-1/2" collets. On my SB 10K it allows just over 3/4" bar though the spindle as opposed to stock 5/8" limit 6K collets since there is no draw tube. This is quite a useful addition.

AFA on my Hardinges, the stock spindle will take 1-1/4" through the spindle with key removed. But the stock 5c collet system will only pass 1" when in place. With a Jacobs on the nose, a full 1-1/4" bar will pass. Again, not a biggie for people with large lathes, but sometimes useful to us with smaller ones. As you can tell, i have complete 5c systems on several Hardinge lathes including all the step chuck closers and large pie collests. & Buck-Forkhardt chucks. Sometimes the Jacobs is an easy solution to an aggravating situation. The range of a single Jacobs collet is also nice for bar and parts that are not ground on-size.

If your lathe was built with 5c nose and lever closer, that is hard to beat especially for bar work since the spindle need never stop. But Jacobs is a nice problem solver or convenience option for many apps.

Here is a link to my experience mounting a Jacobs 9- series on my SB 10K
https://www.practicalmachinist.com/...le-mount-q-204506/?highlight=jacobs+backplate

The picture links are broken, here are some of them again:

I used the straight test bar, centered and indicated straight (dial in TS) as the base reference, to establish the A taper on the taper attachment (short, so it could be done just on the compound) as shown in the picture. Note the micrometer standard to positively establish travel. Then a long travel indicator was used to adjust the taper attachment to the tangent.



As noted in the linked description, the chuck center up well but both it and the collets sometimes need a bump or 2 to dial in "perfectly".







smt

You can buy new collets from Newman Tools. 800 465-1384

Jimsehr