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BISON 6 jaw set tru backplate question

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Swerdk

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#1
Using PM 1236 lathe with standard D1-4 camlock spindle mount attached to stock Chinese 3 jaw chuck. I want to upgrade to Bison set tru and wanted to know if the D 1-4 camlock ( from old chuck) would fit the new chuck or do I need to get a dedicated backplate specific to Bison chuck. I was hoping to save some $$ since I would not need other chuck


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benmychree

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#2
I would have to doubt that, the backplate for a SetTru would have a diameter near the bore for the adjusting setscrews to bear against, something that the present backplate would not have.
 

francist

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#3
image.png
 

Swerdk

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#4
Can you help me understand what the picture is telling me I apologize I’m new to this


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francist

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#5
It's a cross section of a D1-4 back plate for the Set True chucks. From the TMX website. You can see what John was referring to with the extended neck out front for the adjustment screws to bear against.

Sorry, didn't mean to be cryptic.

-frank
 

rock_breaker

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#6
I would contact PM and the manufacturer or distributor of Bison Chucks. Having two lathes one with D-4 the other with a 1-1/2 tpi backing plate on my Bison chuck I think it could be done, but from doing this on a different chuck the machine work must be meticulously done with respect to run out.
I lucked out in that I have a friend with a rotary table on his mill that helped me mount a backing plate on a different chuck.
Hopefully more experienced machinists will respond to your question.
 

benmychree

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#7
It's a cross section of a D1-4 back plate for the Set True chucks. From the TMX website. You can see what John was referring to with the extended neck out front for the adjustment screws to bear against.

Sorry, didn't mean to be cryptic.

-frank
Yes, a normal chuck (not a SetTru) would not have the projecting neck for the adjusting screws to bear against; bite the bullet and buy the proper backplate.
 

Swerdk

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#8
Ouch- okay I appreciate it. Thank you for the expertise


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francist

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#9
Hardly an expert, just good at searching! ;)

-frank
 

wrmiller

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#10
All set-tru chucks I'm familiar with have a special backing plate. Yea, it's a bit of a bummer having to spend the extra cash. Sorry about that. :)

I have had set-tru chucks on my last previous lathe, as well as my current lathe. I have the requirement of being able to chuck up an existing part with minimal TIR, and my set-tru allows me to do that without having to switch to my four-jaw that I've never used. Yet.

Took a bit to get used to dialing one in, but now it's real quick and easy for me.

Have fun with yours. :encourage:
 

ddickey

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#11
Can you get a direct mount?
 

Swerdk

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#12
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.




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mksj

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#13
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.
 

Janderso

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#14
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.
 

rock_breaker

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#15
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.
 

wrmiller

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#16
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. :)
 

mikey

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#17
Different ways to accomplish the same thing. :)
Nah, more of us have 4 jaw independent chucks, that's all. If we all owned Bison Set-Tru chucks then we would be singing a different tune! Only matters on a second op anyway.
 

Doubleeboy

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#18
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.
 

wrmiller

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#19
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
 

Rich V

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#20
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.
 

petertha

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#21
You might also want to check out Gator 'Tech-Tru' chuck + back plate combo. As someone else suggested, harvesting their back plate for a Bison chuck has high probability of fitting since (as I heard it) Gator was entirely based on Bisons dimensions to begin with. My 6" 3J and 8" 4J are both Bison & they are very nice. But the price has become completely stupid, at least here in Canada. Last year I bought a smaller Gator 5" for a rotary table & just because the price was reasonable, included their D1-4 backplate in the order. The back plate fit my lathe spindle nose perfectly. It was semi-machined so in-situ turning to fit the chuck recess gives about the best chance one can expect from the conventional type mount. That chuck repeats to within 0.001" on the lathe, which is about the same as my Bison integrated 3J. Opinions vary on Gator so I will leave you to research this forum & others. I've heard quality might vary based on when it purchased so factor that in. One story goes: great to spotty (as they/Asia converted production to cnc) then good again more recently (teething pains resolved). I would say in my case Gator was ~75-80% of the Bison quality where it counts, but for substantially less cost where I could buy 2 Gators for 1 Bison. Your prices may vary so its kind of situation specific.

I have not purchased Gators tech-tru system yet so cant comment on that. I would guess similar results. The set screws allow you to dial in the spindle/chuck axis very accurately whereas an integrated chuck you get what you get unless you are into jaw grinding. So even with set tru dialed in perfectly the question becomes how well the jaws repeat on stock and also repeat-ability as a function of diameter. Some folks don't factor this in or don't discuss much. Repeat of 0.0004" on a 1" dowel pin is nice, but if the same chuck yields 0.0015" on 2" pin, that's somewhat deflating. I can fiddle my repeat on the Bison 3J +/- 0.001" just by jaw tightening sequence/torque, changing D1 pin clock position, phase of the moon etc. Beyond this, its probably time to think about accurate collet chucks or 4J depending on the application, accuracy & if production time is an issue. Just my own personal views.

http://gatorchucksonline.com/Scroll-Chucks/Tech-Tru/PA-Series/Gator-PA-Series-Main.htm
 
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mikey

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#22
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.
Interesting. Most of us find a set-tru accurate for the size we've adjusted it for but the adjustment doesn't necessarily hold true for other sized stock at the same setting, at least not less than a tenth.
 

francist

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#23
10/1000 = "ten one-thousandths"
1/10,000 = "one ten-thousandth"

Not trying to be difficult and I'm pretty sure I understand what the OP meant, but there is a real difference in measurement between the two.

-frank
 

mikey

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#24
I was "projecting" what I thought he meant.
 

Rich V

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#25
0.01 not 0.0001 inches
 

mikey

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#26
Okay, projected wrong but my point is that a set tru chuck is great for the work that it is dialed in for but will not usually hold tight tolerances for other work unless it is reset for that work. Well, at least that is true for my Yuasa set tru chuck.
 

wrmiller

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#27
If I'm chucking up something in the +/- .5" range from the original piece adjusted to, I'm good. Beyond that, I always check. I'm SO glad I bought my 8" PB before I was forced into retirement. It's the most accurate 3-jaw chuck I've owned.
 
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