6 Jaw vs 4 chuck any users

[Jinx-)]

I'm big fan of 4 jaw chuck and rather stay away from 3 since anytime time I true anything on it I'm getting runout, but some people say 6 jaw is the perfection of all... Whatever..,,, I can index anything I need on 4 jaw and run true... So am I wrong?

[lazylabs]

Here is my take although I am a semi-machinist not a paid pro. The six will give you a little more even grip pressure on anything thin walled. If you use them on an adjust tru backplane then you get the dial in capability of the 4 jaw with the improved gripping power. If your using them as an improved 3 jaw on round stock they tend to be a little more accurate as far as just chuck and go. I would think that if you took a 3 or 6 QUALITY chuck on a fixed back plate on a solid piece of round stock they would be the same. If you took the six jaw on a piece of thin tubing with an adjust tru back plate you would exemplify the differences....... sorry to ramble just my simple way of seeing it.

[shortgrass]

Originally Posted by Jinx-)

I'm big fan of 4 jaw chuck and rather stay away from 3 since anytime time I true anything on it I'm getting runout, but some people say 6 jaw is the perfection of all... Whatever..,,, I can index anything I need on 4 jaw and run true... So am I wrong?

You're comparing "apples to oranges". The 3 jaw is a scroll chuck, all jaws move when you turn the key. Unless your 4 jaw is a "scroll chuck", it is an "independent" jaw chuck, meaning only one jaw moves at a time when you turn the key allowing a piece to be centered using an indicator . Many 3 jaw scroll chucks are not built on center as close as they should be. I have seen (and used) 3 jaw "independent" chucks. They're a pain!. I've used 4 jaw "scroll" chucks. They allow a square to be held as well as round pieces. The "True Set" mentioned in a previous post is available in 3 or 6 jaw. The 6 jaw, as mentioned holds thin sectioned pieces better (without crushing them or 'egging' them). The "true set" feature is nice for short 'production runs' of pieces the same size. I feel the best 3 jaw scroll chuck is one mounted on a back plate where the back plate has been trued to the machine. In the case of a D1 series mount I like to 'witness mark' it, so the same stud goes in the same hole if I remove it. A chuck mounted on a back plate can be centered up to run better than most 3 jaws scrolls built with an intgral mount. If I had only one chuck, it would have to be a 4 jaw indepndent. Would work for anything.

[J E Custom]

They all have there advantages.

3 jaw= fast and convenient but not as versatile as other chucks.
4 jaw= slower to set up because of the individual adjustments on each jaw but
very precise and they are able to hold something other than a round accuratly
centered.
6 jaw=better grip, most 6 jaw chucks are fully adjustable and can be trued for fast
accurate use. they are also the most expensive.

Like shortgrass, If I could have only one chuck it would be a 4 jaw.

J E CUSTOM

[ken snyder]

6 jaw for thin stuff that you do not want to distort. 4 jaw independent for TIR ( one of the adjustable set true ) 3 jaw for everything else. The amount of Taper just by differences of locking down a tail stock will generally surpass the chuck concern by a land slide. Once a part gets out far enough to need a center the chuck is of less importance than the lathes setup and the machinists attention to detail in making his set up.

[Trickymissfit]

Originally Posted by Jinx-)

I'm big fan of 4 jaw chuck and rather stay away from 3 since anytime time I true anything on it I'm getting runout, but some people say 6 jaw is the perfection of all... Whatever..,,, I can index anything I need on 4 jaw and run true... So am I wrong?

they make three jaw chucks that can be adjusted to zero run out. Look for a Buck Chuck (by the way the best chucks made). I like four jaw chucks, but they wont do everything just like a three jaw wont as well.
gary

[Trickymissfit]

Originally Posted by lazylabs

Here is my take although I am a semi-machinist not a paid pro. The six will give you a little more even grip pressure on anything thin walled. If you use them on an adjust tru backplane then you get the dial in capability of the 4 jaw with the improved gripping power. If your using them as an improved 3 jaw on round stock they tend to be a little more accurate as far as just chuck and go. I would think that if you took a 3 or 6 QUALITY chuck on a fixed back plate on a solid piece of round stock they would be the same. If you took the six jaw on a piece of thin tubing with an adjust tru back plate you would exemplify the differences....... sorry to ramble just my simple way of seeing it.

I think we are all talking apples to oranges here. The better chucks are scroll chucks, and as I said a Buck is by far the best you can buy. All chucks will collapse the piece your turning if you use enough pressure on the jaws. Most guys that use their chucks daily keep several sets of jaws laying around for different aps. The way to get the best grip on the stock with the least pressure is to cut the jaws in to fit the O.D. of the part. Still when your looking at something that has a .06" wall you really need to go in another direction. A collet will work better here, but you can also make up a device to hold the thin walled stuff, and still cuck it up. The problem will a six jaw and the others is that the actual pressure exerted is in a small area, where a collet is over a much broader surface area.
gary