Adjust-Tru Bison

[mountainshadows]

I was looking at this recently myself. I bought a Bison 5C Set-Tru at Ajax. At the time I found their prices to be pretty competitive on new.

The 6"-6J Gator works out to 1195 USD including D1-4 Adjust-Tru backplate

6" GATOR Lathe Chuck 6 Jaw TRU ADJUSTABLE + ADAPTER FORGED

The Bison 6"-6J forged Set-Tru is 1635 USD including back plate as combo

6 1/4" Bison 6 Jaw "SetTru" Forged Lathe Chuck + Adapter Plate

If you buy the chuck (7-868-0600) and backplate (7-875-063) separately it works out to 1294+364=1658

A bump from the way back machine. I have a (new to me) Cazeneuve HBX 360 with a chinese 3 jaw on it that I would like to replace. I have a Super Spacer with an 8" Bison 3 jaw that won't fit due to the backing plate. The fix I think will be to mill a new backing plate.

Anyway, as a new member here I was reading through threads and trying to pick up knowledge as I'm new to machining, and as I was reading through this thread I thought I would click on the links in the above post. What I found interesting is that the Gator chuck is still $1195 and the Bison is now $2165!
I thought it interesting the increase in price and not the other.........but maybe I'm missing something.

 

[petertha]

I forgot I posted that when I was evaluating the two brands. Interesting about the current price discrepancy. It appears the Gator includes the backplate in the price in the title description & drop down so it doesn't look like a typo. Best to call & confirm but I have also noticed Bison price creep as well. Once upon a time they used to be a good quality, half price alternative to higher end brands but times have changed. I have 5" 2-part jaw Gator chucks. Overall I would say 90% of Bison quality but most of that is finish. TIR is comparable & jaws fit well in the slots. The scroll wasn't quite as smooth but not horrible, being picky here. I've also heard its a moving target with them depending on when you purchased. QC kind of went up & down & up again. But seems like many Asian chuck makers are up-ing their game so maybe there is hope (and performance pressure).

On a related note, I tried posting a Set-Tru observation elsewhere, but this forum was having issues at the time so I don't think I ever went back to re-post. I have a Bison D1-4 ST in both 5C collet chuck & ultimately decided to buy the ST 6" 6-J chuck mentioned, luckily before the price increase. Using the radial adjusting set screws I dialed them in within a tenth & of course tightened the front retention bolts to retain that position, re-confirm TIR etc. I have a mark indicating the (D1-4) pins so they engage to the same spots each time. I carried on my merry way with no issues.

I normally use a regular 3J chuck for everyday work, so the ST's were on the shelf. When I remounted the 5C Set-Tru I knew something was fishy, it was off by 0.0035". I removed the collet & measured the 5C seat itself, exact same result & clock position. In other words runout was not due to the part or the collet. All the screws were tight including the front face screws. I reset concentricity using DTI, again within a tenth. About a week later I checked again, its off by 0.001". The lathe spindle is accurate so no issues there. Same test method, same test apparatus, same shop temp etc.

I've been repeating the same test with my Set-Tru 6J chuck. Its a similar effect but not to same degree. Drift is say 0.0010 - 0.0015". If it stays on the spindle I can't detect much change. So its almost like its stress relieving when off the lathe. Maybe because no spindle nose to offer support? Maybe thicker body 6" distorts less? I could not find a Bison torque spec for radial set screws, they just say equal. Lately I have been taking care to set them lighter, just enough to retain the position but avoiding overgronk especially because they must be very fine pitch. This seems to be helping although I'm not quite to the bottom of the issue. My conclusion is that these ST chucks are not set-and-forget. It just allows you to tweak & dial them in, which I suppose is better than regrinding jaws. Maybe I misunderstood this from the get-go. Tweaking them once or twice a year I'd be OK with, but if its very often, that's kind of a bummer for the cost.

Links. Bison just say 'equally tightened'
https://bison-chuck.com/wp-content/uploads/2021/06/Manual-3200_3500-1001-01.pdf

Very informative video by Rob Renzetti on chuck body distortion

 

[Dabbler]

@ddickey you can sell your D1-6 backplate here, abnd recoup some of the investment if you end up with it. Me and others have lathes with D1-6...

 

[RickKr]

Oh, and there is also a Bison 5" dia 6J Set-Tru at lower cost if you don't need the extra inch capacity. I don't know if Gator makes a 5", didn't check.

5" BISON 6 Jaw SET-TRU Chuck Forged Steel 7-868-0500

I have had this chuck for close to 20 yrs, first purchased for a SB9A with Bison backplate, later fitted to a pre-WWII Rivet 1020 and currently with a D1-3 for a Monarch 10EE. I love it and used it preferentially over others even when a 6J was not needed. Note, however, that the jaws do not come to a fine point, so it has a larger minimum diameter capacity than might be expected. I was not particularly aware of this until I inherited a 6" Buck Set-Tru 6J. Not I mostly use the Buck.

Back when I restored the pre-WWII Rivett 1020 (avatar image and in my introduction post/thread), I had to machine backplates as it was an L00 taper with non-standard 4tpi locking threads and none were available. Machined a number of backplates (first image), but for the Bison 6J, I had to machine an insert for the adjust-tru hub. Pictured is the machined backplate on the Rivett spindle, the insert to be screwed into the backplate and the original threaded Bison backplate that was purchased along with the chuck, for the SB9A.

The point is, one can make their own adjust-tru backplate from a standard backplate.

I think the Bison chucks are excellent. In addition to the 5" 6J, I have their 5C Adjust-Tru Collet chuck, and an 8", 3J Adjust-Tru both on on D1-3 backplates. Plus a 6" 4J Bison that has lived through the sequence of SB9A, Rivett 1020 and Monarch 10EE.