BISON 6 jaw set tru backplate question

4 jaw is a bit of an art. Tried it for the first time last weekend after t three years owning one

When I order the bison or maybe TMX. I’m gonna look at all possible connections now that I am heavily encouraged to get a new backplate.




Sent from my iPhone using Tapatalk
 
Gator chucks and back plates are for the most part interchangeable so you can save about 50-60% using a Gator back plate with a Bison chuck. My Bison 4J combo uses a Gator back plate and it was within 0.0001" flatness. Bison and TMX are pretty much the same company, although there can be slight differences from what I have seen. Not sure if just a change in model or they are two separate lines. I will say that I have several Bison chucks and have been very satisfied with their performance and fit/finish. Gator is mixed bag as far as quality.
 
I'm new to this game as well, I found I have about .012 to .015" TIR on the outside of my Cushman 6" 4 Jaw Chuck.
(This is a threaded spindle, 1 7/8 8 TPI) When I dial in a piece of stock, I can get it down to <.002" on the piece held in the jaws, the business end.
I assumed the chuck was junk, but, the piece I am turning is well supported and runs true. Well, true as I can get it.
The "art" for me was fairly intuitive, I was surprised how easy it is to dial in a 4 jaw.
 
I recently re-learned a 4 jaw technique that the machine shop instructor tried to teach us which is: After getting the work close by the circles on the chuck face get two opposing jaws close to center then turn 90` and bring those jaws to the same reading as the first set. Continue to center the second set to 0 run out then turn 90` to bring the first set to 0 run out. Final adjustment may be required but it certainly decreases the time required for set up. Two chuck wrenches are an advantage but not totally necessary. This no doubt is the way it is taught in machinist classes but this self taught hobbyist did it with a lot of spinning and adjusting.
 
All about personal preference I guess.

I don't do non-round stuff in my lathe, as that is what my mill is for. And I have no desire to spend the time setting up round stuff in a four-jaw.

When making a new part, I just chuck up a piece of material and go. When I'm cutting on a existing part and accuracy is needed, I dial in the set-tru.

Different ways to accomplish the same thing. :)
 
On a round part being chucked up for first time with no repeat identical part to be chucked up after, there is no contest, 4 jaw beats the Bison Set tru by a large margin for speed. Do enough work with a 4 jaw truing a work piece can be measured in seconds not minutes. If I had a zillion identical diameter parts to chuck and do an op on, the set tru wins, but if part is with in the range of my collet set up that is what I would use for speed. Holding a part to a tolerance of a couple tenths is just as easy on a 4 jaw as set tru and frequently faster except the repeat set up for similar parts. Different strokes, different folks. Another conderation is 6 jaws have less holding power than 4 jaw or 3 jaw, where 6 jaw excels is thin wall parts that can crush or distort easily.
 
If I set up a part in my PB, and then have to re-chuck it or another piece of a similar size, I rarely have to adjust the chuck. The PB repeats well. I have no experience with the Bison, but I hear it is a good quality chuck.

Some folks say they are faster setting up a 4-jaw than a set-tru. That's cool, but I'm way faster setting up my set-tru than a four jaw. Different folks, different strokes. :D
 
A "set true" style back plate is easy to make from a standard back plate. Just need to attach a cored disk to the back plate for the set true adjusting screws with a thru hole to match the chucks in size. If $$ is a concern I would adapt an existing back plate otherwise buy one and be done.

As for a 4 jaw being faster than a set true chuck I don't see this as being the case. A set true chuck is a 4 jaw chuck (with limited adjustment range) combined with a scroll chuck. My 10in 6 jaw set true is very fast to center and once centered is off by less than 10/1000 over it's full range. Takes very little time to adjust for a few thousandths vs a 4 jaw off by ten times that amount.

A 4 jaw is superior to a scroll for mounting irregular shaped stock and the fact that a 4 jaw can exert more holding power than a scroll.
 
Back
Top