# 6 Jaw Chucks



## chevydyl (Jul 5, 2013)

So the 3 jaw chuck that came with my old atlas is wasted, teeth were missing from the pinion, there's no name brand on it just made in England stamped on the back. So in the mean time i have been using the like new 4 jaw that also came with the lathe but I would like to replace the 3 jaw. Aside from the gorgeous look of a 6 jaw what are the drawbacks I'm looking at a chinese made zero set scroll type i would be into it Almost 400 for a 6" with a threaded back plate. I want the ease of a scroll type but dig the fact tha you can hold more delicate objects with the six. And as mentioned they just plain look great. The one in question also has two piece reversible jaws and they claim .0005 TIR repeatability. Mone isn't the issue I don't mind paying more than double what the same manufacture offers in a 3 jaw


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## Ray C (Jul 5, 2013)

If you don't mind, I'd like to add some questions to yours as I too am curious about 6 jaw chucks.

Do all 6 jaws work in unison?  And for the ones which have jaw faces which are bolted on, can jaw alignment be achieved by loosening those bolts so you can get a perfect centering?


Thanks


Ray


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## 8ntsane (Jul 5, 2013)

Sounds like you doing work on thin wall tube and such. Having the ajust true function is a good thing. Also the bolt on jaws are a good thing, and make it faster for you to turn them around. As I remove each jaw, I give each jaw a quick blast of air to remove any dirt grit or other. The chuck side get a carefull wipe instead of air. You got to make certain things are clean, or your jaws wont be right when you tighten them down.

One thing I have noticed with the 6-jaw chucks over the years. The chuck body is not as robust , and don't fair well to a crash, even a minor one. Im only guessing its because of all the jaw slots machined in them. Depending on your machine of coarse, but some lathes are equipped with collar that can be locked down a set distance to kick the lathe out of gear when feeding towards the chuck. I use mine when I need to repeatedly feed close to the chuck.

The 6 jaw is more a purpose driven chuck for thin wall tube or the like. But can be used for regular work, as many do. The 6 jaw does have the extra jaws to spread out the clamping forces to the work piece, but from what Ive seen the contact area the grips the work piece is very narrow. That could be brand to brand, or the normal deal, not sure.

When you get your new chuck, post up some pics, we all like pics .

You mention the Chinese chuck being a possible drawback. But, there is higher end chucks out there. I have seen other on this board post up pics of several brands. I sure some will chime in with thoughts on this. To some extent we do get what we pay for. Some other that have purchased current off shore 6- jaw chucks might be able to shed more light on this.


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## chevydyl (Jul 5, 2013)

I only want to have to buy one chuck so do I get a 6 or an 8". The 8 is a full 21lbs heavier for a total of 40lbs seems pretty heavy to be hanging off the front of the atlas 12". So I think the 6 is the one to get.  I don't see myself needingto grab anything larger than 6"


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## george wilson (Jul 5, 2013)

A 6 jaw chuck doesn't grip as well as a 3 jaw. As mentioned,it is really for thin stuff like tubing. It applies more grip spots so you don't damage the tubing by crushing it so easily.


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## GaryK (Jul 5, 2013)

george wilson said:


> A 6 jaw chuck doesn't grip as well as a 3 jaw. As mentioned,it is really for thin stuff like tubing. It applies more grip spots so you don't damage the tubing by crushing it so easily.



If you need better grip you just remove 3 of the jaws. You can also us it as a 2 or 4 jaw chuck (not with independent jaw movement) if you need to.

I bought a Fuerda Gator 6 jaw chuck (fantastic chuck by the way) about 6 months ago and have never used my 3 jaw since. A 6 jaw gives you more options than a 3 jaw by far.
The only drawback to a 6 jaw is the size of the smallest diameter you can hold. Mine is about 3/8". Since I have the option of removing 3 of the jaws that is not a problem.
I can revert it to a 3 jaw.

If you are interested you can see my chuck HERE.

Gary


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## 8ntsane (Jul 5, 2013)

Gary
That is a very nice looking chuck you purchased :thumbzup:
I do have a question though. How do you figure you get better grip removing 3 of the jaws?
I can see being able to close the jaws on a smaller work piece, but as you said,you would use a collet anyway.
Just makes me wonder, as I was told yrs ago by I think a KBC salesman, that the contact points of the 6 jaw chucks being very narrow needed to have all 6 jaws used, unless the job didn't require much gripping force. So by removing 3 jaws, I was told that I just reduced the grip by 50 per cent. Just what I was told, I never thought about it again till now. Just wondering if anyone knows the deal on that.

Chevy
I see your concern with the weight of the two chucks in question. I don,t know the brand of your machine to comment on whats too big, and or heavy. You might want to start a new thread asking others with the same machine, what they have been using. The set true chucks have more weight because of the back plate has more material to it. From what Ive seen the chuck body is slightly longer too. Yrs back I had a 12X37 import lathe, the standard chuck that came on the machine was a 8 inch. But , if you think the 6 will fill your needs, its all good.


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## jamie76x (Jul 5, 2013)

6 Jaw chucks are great for holding work that is allready turned or ground. If the work piece is not perfectly round it will tend to spin since not all 6 jaws will have equal pressure on the work piece. You can take 3 jaws out that will cure the problem ... But has a down side. Now chips get into the scrolls and tracks.  You know, there isnt anything wrong with using a 4 jaw. It may be a pain indicationg every work piece in, but then again if you want to do good work you Indicate everything in anyhow. It just wastes time indicationg things in that don't have to be perfect.


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## GaryK (Jul 5, 2013)

8ntsane said:


> Gary
> I was told that I just reduced the grip by 50 per cent.



It would be just the opposite of that. Just think of a smooth jaw pair of pliers vs a pair with serrated jaws.

A serrated jaw would provide more force concentrated into a smaller area giving it more "bite".

That's about the only analogy I could come up with at this time.

Gary


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## GaryK (Jul 5, 2013)

jamie76x said:


> 6 Jaw chucks are great for holding work that is allready turned or ground. If the work piece is not perfectly round it will tend to spin since not all 6 jaws will have equal pressure on the work piece.



Not to be argumentative, but unequal pressure wouldn't necessarily allow something to spin. Not enough pressure would though.
For example if only 3 to 5 of the jaws were providing adequate pressure it wouldn't spin.





jamie76x said:


> You can take 3 jaws out that will cure the problem ... But  has a down side. Now chips get into the scrolls and tracks. .



That's one reason to get a 6 jaw chuck with 2 piece jaws.


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## Tony Wells (Jul 5, 2013)

Question, Gary. If you remove the top jaws, aren't the master jaws still in contact with the work? In my observation, a properly ground chuck has master and top jaws ground together to provide maximum length of grip.


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## 8ntsane (Jul 5, 2013)

Tony Wells said:


> Question, Gary. If you remove the top jaws, aren't the master jaws still in contact with the work? In my observation, a properly ground chuck has master and top jaws ground together to provide maximum length of grip.



On my 2-pc jaws they would be, but you could get away with it if the work piece didn't go in past the face of the chuck, I think?
I allways thought that the more surface of the jaw in contact of the work piece provides a better clamping action. I guess the biz I was in for so many yrs has me thinking this way. I relate it to race tires (Drag cars) in my case. They have no treads, as that makes spaces between them, and would reduce the contact patch area that sits on the pavement, and would effect the grip, and traction. Not to be confused with any other race tire, like rain tires.

Just another thought come to mind. When I need to machine a part that I know must not be marred up with any jaw marks, I use the soft jaws, and bore to size. These are very wide contact patch to the work piece, and grip extremely well. No groove s at all cut in them, just full contact. Gary may be right in his way of thinking, maybe I have it all bass ackwards, lol. Almost worth a call to Bison and get the story from them.


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## Tony Wells (Jul 5, 2013)

I guess I wasn't thinking of NOT swallowing the work fully within the chuck. What you say is true. I think on the chucking pressure, maybe the proper way to think of it is distributed clamping force. The angles of the jaws and scroll determine the ultimate pressure, so if you don't divide it by 6, and use only 3 of the jaws, it must be concentrated on the used jaws.....hence doubling the PSI of the jaws in use. The advantage I see with 6 jaws is exactly the opposite, it distributes force X over 6 (albeit smaller) surfaces, resulting in less PSI. But on the other hand, if the contact area is less, as it could easily be, that distribution factor could be negated and the ultimate chucking force near equal.


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## george wilson (Jul 5, 2013)

I'd rather use a 6 jaw when it is needed than take jaws out and get chips and metal dust into the open slots. Perhaps tape over them. The 6 jaw is still more delicate than a 3 jaw. Look how thin the metal is between those "pie slices". So I save mine for thin stuff. My favorite chuck is my Bison 4 jaw universal chuck. You can grip round or square with it. For hex, you must use the 3 jaw,or the 6 jaw.

It doesn't take much to spring a delicate chuck out of truth.


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## GaryK (Jul 5, 2013)

Tony Wells said:


> Question, Gary. If you remove the top jaws, aren't the master jaws still in contact with the work? In my observation, a properly ground chuck has master and top jaws ground together to provide maximum length of grip.



That's true if the work extended more than 1.5" into the chuck.


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