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8" Bison 4 Jaw Combination Chuck

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#1
I just bought an 8” Bison 4 Jaw Combination chuck for use on my PM1340GT.

I know there are members here that own and use this chuck.

While this chuck has been discussed in a few snippets here and there in other threads, I don’t believe there is a thread focused on it. So I wanted to start one to hopefully collect insights in one spot for folks who may find it helpful. (I believe there are four other members here who just ordered this chuck and will be receiving them in the next few days.)

So to get us started:

1. What are the pros and cons of this chuck?

2. Can you offer any advice for a new user for this specific chuck?

Here are some photos of my chuck out of the box, cleaned up and ready to go:

new bison.jpg

IMG_20170915_172555.jpg

Made in Poland.jpg

Adapter.jpg
 
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#2
Nice!

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ddickey

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#3
Nice, D1-4 mount?
 
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#4
Hi Alan,
Great chuck! Mark (mksj) turned me on to an extra one (NIB) he had. I machined my own mounting plate and its dead on. You'll want to make two mini T-handles with magnets for quick work in dialing in pieces. Mark gifted me his originals and I love them. Once you play with it some, you'll be able to dial in in under three-four minutes. I always register my chucks to my spindle with a small center punch mark prior to removing the turned mounting plate. The repeatability on these chucks are phenomenal. The only cons I have is swarf fouling during boring operation and the added weight but thats the nature of the beast.

Registering the back plate
IMG_1264.JPG
Running true.
IMG_1265.JPG
Between this chuck and the 5C system, I have not used the three jaw since.

The two low profile T-handles allow for complete rotation while the small inset magnets hold them in place.
IMG_1687.JPG
Its an amazing chuck that brings machining tolerances fast and easy when removing/reinstalling your work piece for second operations.

It holds the work well without over torquing.
IMG_1688.JPG
I'm sure Mark will chime in on the details of the mini T's and magnets.

Money well spent in time saving and end results.
I hope this helps
 
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#5
Nice, D1-4 mount?
Yes - fits the PM1340G lathe. The adapter plate is a model 7-878-084F which is a newer model number.
 

ddickey

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#6
Yes - fits the PM1340G lathe. The adapter plate is a model 7-878-084F which is a newer model number.
Okay, I was thinking maybe it was a direct mount.
 
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#7
I checked the runout of the face of the Bison adapter plate on the lathe. I used a B&S Valueline that I keep handy - no runout. Swapped to a Starrett .0001" indicator - not really anything detectable other than some surface finish vibes. I am quite pleased.

I must say that I am also pleased with the PM1340GT spindle!

 

Bamban

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#8
I have one coming, it must have been the last one in their inventory at that sale price Mark alerted me on.

When I get mine all checked out I will verify its merit on barrel work and let you guys know. I have an 8 inch 6J Bison set thru I can compare it with. If it proves to be better than the set thru chuck, the set thru will be up for sale. If not this combo chuck will be up for sale.
 

Bamban

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#9
Mark,

I am definitely interested in seeing details of the mini wrenches. When I needed to use the 4J on the Jet 1024, I took the lazy route and bought T handled Allen wrenches from eBay and cut them to fit. I dont think I will use the same Bubba solution on this nice combination chuck.

20170917_120328.jpg
 
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mksj

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#10
Chuck keys for independent jaws are made from 3/4" drill rod and are 1.85" in overall length. The T bar is 7" and held in with a set screw, the back is drilled to make them lighter. The key tip has a small Neodymium magnet that holds it in the chuck so you can rotate the chuck and not have the keys fall out.
Bison Chuck Keys.jpg 20170727_165938.jpg

Like firestopper/Paco, the Bison combo chucks is only second to my 5C as far as use on the lathe. I have a nice 3J Set-Tru 6" PBA, but rarely use it. I prefer the 4J combo for most work, and usually it is very quick to dial in a part, the scroll portion will repeat as well as most chucks (usually better than 0.002"). Since you can tweak the pressure on all 4 jaws, I find it holds stock very well.
 

ddickey

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#11
What's MKSJ?
 
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#13
That would be Mark, the builder of many of the variable speed control systems on the PM1340GT lathes, mine included. He is a an electrical controls wizard plus he knows a lot about this hobby of ours!

EDIT: should have said that he's also built controls for lots of other lathes, mills, and machine tools in addition to the PM1340's.
 
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#14
Mark and Paco, how do you gents handle this little chuck? It is a bit heavy isn't it? Did you build a sled to help mount it or do you simply mule it on there?
 

mksj

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#15
Most of the time, two hands, preferably dry, not too old yet that I can't pick it up and get it in place. I have a padded insert block that locks in position on top of the ways, I use it whenever I am changing chucks. Just for safety, as the chucks can slip. I mark my chucks so they always go in in the same position, I have the key in the top cam-lock, so I hold the chuck in place with one hand and lock one pin with the other. David Best made a very nice chuck holding sled that fits on his ways, probably a better way to go.
 
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#16
Chuck keys for independent jaws are made from 3/4" drill rod and are 1.85" in overall length. The T bar is 7" and held in with a set screw, the back is drilled to make them lighter. The key tip has a small Neodymium magnet that holds it in the chuck so you can rotate the chuck and not have the keys fall out.
View attachment 241779 View attachment 241780

. . . . . . . . . . . .
Mark, what diameter is the T bar - 1/4"?
 
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#17
I do the same as Mark. I took a piece of 3/4" plywood, cut it to cover the ways and brad nailed to rail strips that index snugly to the inside portion of the bed ways. It also can double as a platform for tooling when used behind the tail stock. The Bison is hefty, but not that bad for me yet. I like what David Best shared sometime back for his solution as well. I should do the same before long.
I also index all my chucks to the spindle (center punch).
David Best's solution is the "best";)
IMG_7106.jpg
 

mksj

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#18
Mark, what diameter is the T bar - 1/4"?
Yes, 1/4" drill rod. Balance of weight and strength on the T bar. David's chuck carriers are the slickest, but I am already space limited, and I would need a place for the chuck carriers.
 

wildo

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#19
I just bought an 8” Bison 4 Jaw Combination chuck for use on my PM1340GT.
OK- am I being dense here?? What is a "combination" chuck when it relates to a 4 jaw? I have a Bison 3 jaw 6" adjust true chuck, which is what I think of when I think of a combo chuck. The "adjust true" part of it is basically a built in 4 jaw for centering the 3 jaw. But on a 4 jaw chuck... what is the combination? Sorry if that's an obvious question...
 
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#20
I have been using a board to protect the ways when changing chucks. I can "mule" this new one on there but it weighs enough that I decided I did want a sled to make it easier. Made one last night out of maple, sealed it with spar varnish, and it works fine, although it is not to David's standards!
IMG_20170918_082835.jpg

IMG_20170918_083359.jpg
 

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#21
OK- am I being dense here?? What is a "combination" chuck when it relates to a 4 jaw? I have a Bison 3 jaw 6" adjust true chuck, which is what I think of when I think of a combo chuck. The "adjust true" part of it is basically a built in 4 jaw for centering the 3 jaw. But on a 4 jaw chuck... what is the combination? Sorry if that's an obvious question...
Willy,
Good question - it's a 4 jaw scroll chuck with independently adjusting jaws. So you get a scroll and an independent 4 jaw chuck built into one. (i.e. Combination)
 
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bss1

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#22
I guess I'm joining the club also. Mine is scheduled to arrive tomorrow! Thanks for starting this thread Alan.

Mark, those are some nice looking wrenches. Quick question, When you mill the square key on the end, do you place the collet block in your vise vertically or horizontally. The last wrench I made I held the block horizontally but in the end I was wondering if it would have been simpler to have held it in a vertical position.
 
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#23
Not to answer for Mark, but I would hold it horizontal utilizing mostly the end of the cutter. For me, less chance of mucking it up but really can be done both ways so long as you use a stop to index to every time you rotate the collet block.
bss1, your gonna love your new chuck!
 

mksj

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#24
As Paco indicated. I turn the square key portion down on the lathe to the outer diameter of the square corners, then I put it in a square collet block and mill the flats in the horizontal position. I uses a stop that indexes the block (actually the tip of the key) to the same horizontal position so when you rotate it to cut the flats it remains in the same position relative to the end mill. When you cut the flats, I go slightly oversized first, check the fitment, and slowly creep up on the final dimensions with skim cuts. I also break the edges with a fine file and the edges on the key nose. Some some fine fitment with a file gives a nice fit, without very much play. There is a slight taper toward the nose. I thought of heat treating them, but I would rather have the key wear as opposed to the pinion socket.
Mark
 

wildo

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#25
Willy,
Good question - it's a 4 jaw scroll chuck with independently adjusting jaws. So you get a scroll and an independent 4 jaw chuck built into one. (i.e. Combination)
Thanks- super interesting! I'm guessing then that the scroll action is ultimately just to get the chuck jaws close to position quickly?
 

Silverbullet

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#26
Thanks- super interesting! I'm guessing then that the scroll action is ultimately just to get the chuck jaws close to position quickly?
Mostly to keep concetricity for doing more then one operation or multiple parts , like turning 25 square parts and drilling and tapping them.
 

darkzero

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#27
I'm not in the market for one but I have always been curious about these combo chucks. Are the jaws fully independent of the scroll? For example, can you use just the jaws independently or do you have to set the jaws first, then tighten up on the work piece with the scroll? I use my 4 jaw when I really need to bite down on something hard.

I was just wondering cause I see some of you guys using 2 small keys which looks like just for adjustment rather than torquing down with a full size a chuck key.
 

mikey

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#28
This is a very cool chuck! So, if I understand this correctly, you would use this primarily for doing multiples of parts with the same OD? Dial one in with the 4 jaws and then just use the scroll to quickly chuck up all subsequent parts, right? If so, it would be interesting to see how repeatable it is. I would think it would be pretty good when using TGP stock.

So, instead of adjusting the chuck body's concentricity like an adjust-tru chuck does, this chuck does the same thing with the jaws, correct?
 

mksj

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#29
Mikey is correct, just like a Set-Tru chuck but adjusting each jaw on a scroll mechanism instead of the chuck relative to the backing plate. Also a lot quicker then a Set-Tru to adjust. Still, a Set-Tru repeats very well, but there can be some variation depending on the size of the piece and also if the jaws are reversed, it usually requires readjusting the chuck TIR. In my experience, the sequence of tightening the Set-Tru bolts and chuck to the back plate is more critical to setting up the chuck. The combo is a piece of cake, relative to a Set-Tru, but a Set-Tru once set has better repeatability of the scroll.

So with a combination chuck each independent jaw moves on a scroll mechanism carrier which it is attached to a screw mechanism that then adjusts the jaw. Each jaw can be adjusted independently, the scroll moves all 4 jaws simultaneous in whatever position they are set. It makes it easy to remove your work quickly and then reinserting and maintaining the same concentricity. So I usually will use the scroll and tighten down on stock, and then tweak the independent jaws to 0 the TIR. I usually can do this in under a minute, since you are using two keys you can torque bot down, and then turn the chuck 90 degrees and do the other two. Once set, you can just use the scroll and maintain better than 0.002" TIR on repeat parts, but if I need to be spot on I will tweak one of the independent jaws as needed. One aspect that I do like about the 4J with twin keys, is you can get a good feel on the torque/tension that is applied to the jaws. The twin keys have plenty of torque for their size, remember that when using the scroll it is setting the pressure for all four jaws.
 
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darkzero

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#30
Once set, you can just use the scroll and maintain better than 0.002" TIR on repeat
I assumed it would repeat better than that being a quality chuck. I mean I can get my Set-Tru chucks to repeat under .001". Is it because of the movement independent scrolls for each jaws, like when the pressure is released from them when swapping out the workpiece?

I really wanted one these back when I was looking for a chuck. But at the time a 6-jaw was more useful to me. I really hope I don't "need" one of these too. :)
 
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