8" Bison 4 Jaw Combination Chuck

Alan H.

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Sep 17, 2018
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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
 
Nice!

Sent from my SAMSUNG-SM-G920A using Tapatalk
 
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.
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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
 
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!

 
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.
 
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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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.jpg20170727_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.
 
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