Independent vs self-centering 4 jaw chucks: advice?

[seasicksteve]

Don't they make 4-jaw scroll chucks with independent jaws too?

As mentioned they do have 4 jaw scrolls that are adjustable.I have a Skinner Chuck like this It is actually a 4 jaw scroll chuck with unique top jaws that are adjustable. It is a little cumbersome to use and I wouldnt want to put huge amount of torque on it but it is a good piece

 

[STEMtheMachining]

Again, thanks for all the information, even if this was really just confirming what I thought I knew.

Unfortunately, I don't know of a 50 mm 6 jaw chuck with an M12x1 thread, or I'd definitely buy one.

I had a bid on a genuine Unimat 4 jaw, missed it by a dollar.

But from what I can gather, it makes sense to buy the 4 jaw.

I might be stuck with buying the 4 jaw for unimat 3 and a thread reducer.



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[STEMtheMachining]

A 4J scroll is rarely used, one of the issues with 4J and 6J scrolls is that the stock needs to be symmetrical in diameter otherwise there may be an imbalance in the holding of a set of jaws.

Isn't this also the case with a 3 jaw scroll, the piece having to be symmetrical?



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[RJSakowski]

Isn't this also the case with a 3 jaw scroll, the piece having to be symmetrical?



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You can't mount a square shape in a three jaw but anything that more or less resembles a cylinder cab be securely mounted in a three jaw.

Here is an example of mounting an elliptical cylinder in a three jaw.

 

[STEMtheMachining]

You can't mount a square shape in a three jaw but anything that more or less resembles a cylinder cab be securely mounted in a three jaw.

Here is an example of mounting an elliptical cylinder in a three jaw.
View attachment 429108

Right, this is why I'm looking at a 4 jaw, because it'll allow me to work with bar stock as well as asymmetric stock.

The only chuck I currently have is a 3 jaw scroll (with no bully bars, which I plan to make), but my question was if a piece in a 3 jaw scroll has to be symmetrical, which I assume is the case.

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[great white]

All I use now is an independent 4 jaw....but I'm literally a hobbiest. No production or repeated parts here.

 

[STEMtheMachining]

All I use now is an independent 4 jaw....but I'm literally a hobbiest. No production or repeated parts here.

If my lathe had come with a 4 jaw, I'd probably be in the exact same boat.

In fact, I'll probably sell my 3 jaw scroll once I get my 4 jaw independent to recoup the costs, since these things are priced like they're made of gold.



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[homebrewed]

If you get the independent-jaw chuck get yourself another chuck wrench. Adjustments are much easier/faster when you can loosen one side and tighten the other at pretty much the same time. I made one that is long enough to get the wrench handle out of the way of the dial indicator I use for dialing-in parts but that's a nicety not a necessity.

 

[Charles scozzari]

Go with the independent, much more versatile.

I think the 4 jaw would be a much better choice. You can't hold rectangles or make eccentric shafts with a scroll 4 jaw

 

[STEMtheMachining]

If you get the independent-jaw chuck get yourself another chuck wrench. Adjustments are much easier/faster when you can loosen one side and tighten the other at pretty much the same time. I made one that is long enough to get the wrench handle out of the way of the dial indicator I use for dialing-in parts but that's a nicety not a necessity.

This is good advice, thank you.

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