Help choose Ind 4-jaw chuck for 1440GT, please

Rohm makes a 3J combo also. Do they make direct mount combo chucks? if you decide to buy an independent 4J get a direct mount.
 
Took some digging, however, I have been informed that I can be hooked up with a German made Rohm D1-5 8" independent 4-Jaw chuck for, gulp, four thousand dollars. I bet it's a dandy.

I'm 98% settled on a Bison forged steel chuck. Still debating one- vs two-piece jaws.

Hmmmm, early May yet?
Appreciate everyone's input.
 
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oregontripper said:
Took some digging, however, I have been informed that I can be hooked up with a German made Rohm D1-5 8" independent 4-Jaw chuck for, gulp, four thousand dollars. I bet it's a dandy.

I'm 98% settled on a Bison forged steel chuck. Still debating one- vs two-piece jaws.

Hmmmm, early May yet?
Appreciate everyone's input.
Click to expand...
No question, two-piece jaws.
 
I suppose when the two parts of a two piece jaw are properly secured together they function exactly as a one-piece? Any, even the slightest reduction in accuracy?


The machine is planned for applications suitable for the one-piece, whereas there are infinite unknowns I may venture into in the future where a two piece might be useful.
 
oregontripper said:
I suppose when the two parts of a two piece jaw are properly secured together they function exactly as a one-piece? Any, even the slightest reduction in accuracy?


The machine is planned for applications suitable for the one-piece, whereas there are infinite unknowns I may venture into in the future where a two piece might be useful.
Click to expand...
There is no reduction in accuracy and a significant increase in versatility. Custom soft-jaws are not an option with one-piece jaws. I'm surprised they even offer them.
 
Inventory woes... Broadening my scope a bit.

Not sure about what the differences are between a "set-true" and "combination" type chuck? I see Bison offers both.

Information appreciated.
 
All completely different animals. A combination chuck is a scroll chuck (comes in both 3J and 4J) and each jaw rides on a separate screw which allows adjustment same as an independent chuck. So a wide range of adjustment, the scroll repeats to around 0.002" and allows a wide adjustment range for out of round stock or irregular pieces. A Set-Tru style is a scroll chuck with a deeper back plate, there are typically 4 set screw on the chuck that are used to true up the chuck center. The range of adjustment is around 0.005" from center. It requires loosening the chuck slightly from the back plate, making the adjustment and then tightening, it is not really used to center stock but to center the jaws when clamping a precision pin. Scroll chucks will also have some degree of non-linearity in the scroll, so some variation depending on the diameter of the stock you are holding. Weight wise, a combination chuck is the heaviest an 8" with back plate is around 85 lbs, a set-tru scroll around 65 lbs with back plate and a 4J direct mount independent around 50 lbs (depends on if it is forged steel or semi-steel).

If there is an inventory issue with Bison then I would check the forged steel 4J independent in a TMX, they are very close in quality and design.
 
mksj said:
All completely different animals. A combination chuck is a scroll chuck (comes in both 3J and 4J) and each jaw rides on a separate screw which allows adjustment same as an independent chuck. So a wide range of adjustment, the scroll repeats to around 0.002" and allows a wide adjustment range for out of round stock or irregular pieces. A Set-Tru style is a scroll chuck with a deeper back plate, there are typically 4 set screw on the chuck that are used to true up the chuck center. The range of adjustment is around 0.005" from center. It requires loosening the chuck slightly from the back plate, making the adjustment and then tightening, it is not really used to center stock but to center the jaws when clamping a precision pin. Scroll chucks will also have some degree of non-linearity in the scroll, so some variation depending on the diameter of the stock you are holding. Weight wise, a combination chuck is the heaviest an 8" with back plate is around 85 lbs, a set-tru scroll around 65 lbs with back plate and a 4J direct mount independent around 50 lbs (depends on if it is forged steel or semi-steel).

If there is an inventory issue with Bison then I would check the forged steel 4J independent in a TMX, they are very close in quality and design.
Click to expand...
Thanks for that explanation. Great info, I sure don't want a set-true. Checking around and yes TMX is at the top of my list, they sure look good. I'm not in the biggest hurry, so, I will backorder if needed - to get exactly what's desired.
 
The lathe in my "garage-shop". I am 2200 miles away, only, and eager to unwrap it!

Have learned a couple things.

Pratt Burnerd America, Kalimazoo MI, has a "better than cast iron" ductile line of chucks, including independent 4-jaw type of interest. The ductile chucks are made in Czech Republic. Some require a mounting adapter plate, which is the case for the 8" to go D1-5. The adapter is made/machined in Kalamazoo. Their regular cast iron, semi-steel chucks are Chinese. The ductile 8" with D1-5 adapter is rated at 2300 RPM, whereas, the ductile 10" with d1-5 built in is rated at 1700 RPM. (Balanced)

Doesn't appear to be a single 8" 4-jaw forged D1-5 TMX or Bison anywhere. 4-5+ months back order. MSC has offered the best back order price, by a significant margin. Still looking at some options. Some available plain back chucks sure don't look compatible with some of the D1-5 back plates. Chuck mounting holes look to overlap the back plate's D1-5 studs. I don't want excessive depth...


Much thanks to all here. I have come back and referenced comments, that now, all make sense to this bonehead. :D
 
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