Are scrolls in the same size 3 jaw chucks the same?

[Tom Kitta]

I googled and googled and I seem to not be able to find the answer to above question. Say you have two 6" 3 jaw chucks from different manufacturers - will the jaws interchange? I will test this theory today on small sample but I am wondering in more general terms. More specifically are the scrolls very similar? I think the answer is yes - they have to be very close as there simply is no room to be "out" a lot from what is out there especially on smaller chucks. On the other hand we have jaw width - that can be different - but is it?

I have two lathes that came with a Bison 3 jaw 6 1/4 inch chucks aka 160 but are missing external jaws. Getting external jaws from Bison feels expensive. I have also found some master jaws and top jaws (i.e. two piece set) and was also wondering whatever that would fit a Bison that originally was a solid jaw chuck.

What complicates things is that Bison chucks are old - one has "78" stamped on it suggesting its older then me. The code is S160ZJ and what I believe is serial number 0931. I am guessing S stands for semi steel, 160 for size in mm and ZJ is a code for the jaws.

The chuck looks like this guy, made in 81 - https://www.anonse.com/lista/rejon/...rzyszczekowy-nowy-fi-s160zj-oraz-uch-12289009

 

[PeterT]

I have a feeling chuck manufacturers could have different pitches if they are of metric/imperial origin. I have heard of jaws which measured the same pitch but had different width or slot height geometry. You might get lucky Bison to Bison but beyond that, who knows. This might help

http://www.myjawfinder.com/

 

[RobinHood]

I think that is exactly it: the helix is different from manufacturer to manufacturer - so that they can keep you as a repeat customer. If the scroll were to be the same geometry, they can always just make the overall (internal) dimensions ever so slightly different to have you come back to them. Scroll pinions can be different. Also, jaw depth into the body can vary, preventing interchangeability.

I would think that a set of outside jaws would be pricey; I inquired for a set to my 8” Rohm - they were asking $575. Plus I would need to grind them in situ to make them fit accurately (not too big a problem, as I have the tools). I did not get them. Planning on making my own some day...

 

[Dabbler]

Even from the same manufacturer, but different models of the same size, the scrolls can be different. Even getting a new set of jaws from the manufacturer take some work to get the right ones.

 

[Tom Kitta]

So I identified one of the 8" chucks I had (it had the 00 back plate) as Bison by... noticing that a set of Bison soft jaws fit... perfectly into it. The chuck had only 2706 on it as a number. No other Bison identification marks. But I found another 2706 chuck by Bison on sale. This is not Bison identification that is current and date on other 2706 is 92 - so what I may have is transition chuck from early 90s.

So indeed Bison did not change their 8" chuck properties - maybe same will hold true for the 6"?

 

[PeterT]

Consider giving these guys a call.
http://www.lathe-chucks.com/BISON/BISON-MANUAL-CHUCK-INDEX.htm

Long time ago I was asking questions about Bison set-tru, soft jaws, Gator (clone), Bison accessories & he had all the answers. What parts fit what. From what I can see they even sell replacement parts including scrolls so he might be able to make sense of your model#.
ps -down at the bottom of the page are some 'affiliate' web sites that sell all kinds of goodies. One day when I win the lottery I would like some of those aftermarket jaws with replaceable machinable inserts.