8" Bison 4 Jaw Combination Chuck

[Alan H.]

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)

 

[bss1]

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.

 

[Firestopper]

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]

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]

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]

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]

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]

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]

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.

 

[darkzero]

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.