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View Full Version : 3 soft jaws or 6 hard jaws for a given application.



Arthur.Marks
10-08-2011, 12:36 AM
I'm a little torn. Perhaps folks here can offer some thoughts. If you could only have one, would you rather have...

∅4" Rohm ZSU, Item no. 101796. 3-jaw. Flat back. Steel body. 2-piece jaws. Aluminum and steel soft jaws are available, but pie jaws are not. Pointed soft jaw sets are economical (~$40).
∅4" Buck ATSC 6-jaw, Item no. B8046S. Steel body. Hard jaws. Adjust-Tru.

Primary use is for holding ∅2-3" thin-wall 4130 tubing which is to have a bearing seat bored into it. Lathe is an 8" swing manual bench lathe. Other chucks already fitted to this lathe are a standard 4" Bison 3-jaw, a 4" Hardinge independent 4-jaw and a 5" Bison independent 4-jaw. Bison does offer steel "soft" jaws that replace the hard jaws on their 3-jaw chuck, but they are comparatively expensive (~$75/set).

Other than for the specific operation mentioned above, which would you feel better compliments the workholding selection for the lathe. Cost is comparable between the two. Budget prohibits both. It's one or the other. Thoughts?

Black_Moons
10-08-2011, 12:46 AM
Id consider the 6 jaw for the pipe.. since you allready have 3 jaws.

Alternatively, figure out if its economical to make your own pie jaws for the 2 peice 3 jaw, if you plan to do a lot of repeative sized work.

Ultra alternatively, make a pot chuck (Collet really) for the pipe work your doing and use whatever 3 jaw or 4 jaw that you like best.

becksmachine
10-08-2011, 01:42 AM
The six jaw will do a better job of maintaining roundness as compared to a 3 jaw, but boring soft jaws (pie type or otherwise) on the 3 jaw will do that function even better. Especially in larger sizes where the distance between jaws becomes greater.


The downside to soft jaws is the need to make a separate set of jaws for each different OD of material.

Dave

DATo
10-08-2011, 02:19 AM
The six jaw 'Adjust True' would be my choice. That's what we use almost exclusively at work and they have spoiled me rotten. I'd get that one and then keep my eye pealed for an economy three-jaw that will accept machinable blocks. To be perfectly honest, with the exception of some very unique jobs I almost never have the need to use a machinable jaw chuck with those six jaw chucks around.

KEJR
10-08-2011, 09:55 AM
The six jaw 'Adjust True' would be my choice. That's what we use almost exclusively at work and they have spoiled me rotten. I'd get that one and then keep my eye pealed for an economy three-jaw that will accept machinable blocks. To be perfectly honest, with the exception of some very unique jobs I almost never have the need to use a machinable jaw chuck with those six jaw chucks around.

This sounds like sound logic to me. We have 6 jaw bucks at work and they are really nice. I have heard that the new Buck chucks aren't made in the USA anymore and that the "old" buck chucks are being remade by ex Buck employees by Kalamazoo Chuck

http://www.kalamazoochuck.com/

FYI.

At home I have a 3 jaw Fuerda with 2 piece jaws. I don't do much tubing work and I have a full set of 5C collets for stuff up to 1-1/8" I'm pretty happy with this setup as I can make soft jaws or plugs for the occassional large diameter tubing.

KEJR

Black Forest
10-08-2011, 10:11 AM
I have this collection of soft jaws for my lathe. It makes for easy turning on all sizes of material.

http://i853.photobucket.com/albums/ab91/burnandreturn/softjaws.jpg

PixMan
10-08-2011, 10:13 AM
I have this collection of soft jaws for my lathe. It makes for easy turning on all sizes of material.



Show off.

;)

If you got all those with the machine, that really made the deal a huge winner!

vpt
10-08-2011, 10:33 AM
I have this collection of soft jaws for my lathe. It makes for easy turning on all sizes of material.

http://i853.photobucket.com/albums/ab91/burnandreturn/softjaws.jpg



I always though "soft jaws" were aluminum? Are steel jaws that aren't hardened considered soft jaws as well?

PeteM
10-08-2011, 11:22 AM
Soft jaws can be either aluminum or steel.

To the original poster -- if this is a repetitive operation (same tube size, lots of parts) I'd go with the soft jaws. Soft jaws also give you flexibility for odd ball jobs -- the pocket you machine can have all sorts of features. It can hold short work, stepped diameters, parts with "ears" etc. etc.

If it's lots of thin tubing, mostly one-off parts and different diameters, then the 6 jaw makes more sense.

Arthur.Marks
10-08-2011, 11:25 AM
I guess I just have a decision to make. I hadn't really considered the pot chuck/collet. Thinking about it more, it's a balancing act---the ability of the workholding method to hold concentricity (with least distortion to work) is inversely related to its number of various uses.

A few comments--
*Just about all the top jaw manufacturers offer "soft" jaws in a variety of materials. i.e. 1018 plain steel, aluminum. It wouldn't surprise me to learn that the latter outsells the former by a good margin, though, Andy.
*A 4" chuck is really the most appropriate for my lathe. A 5" starts to dwarf it except for the relatively light, short bodied 4-jaws. The Rohm is the only 4" chuck I know of to offer true 2-piece, american tongue & groove soft jaws. Every other manufacturer starts at 5"---others at 6" diameter. In other words, there is no waiting for an economy option. The only one I could imagine is a Taig 3" 3-jaw fitted to a collet arbor.

DATo
10-09-2011, 08:57 AM
Black Forest - I like reading your posts. I find that we agree on most posts and I respect your opinions but I have to take exception to this one. I look at the picture you posted and imagine all the time and material that went into making those soft jaws and shudder. With an adjust true chuck you can fine tune the concentricity within tenths and there is no need to make anything.

I think you have the right idea if the job is a production run of many, many parts though ... especially a job that is repeated from time to time. Also, if one is making many parts at the same time there would be no need to check the concentricity each time. Even with the adjust true I do not trust the concentricity from one part to the next but check each time though most of the time it is not necessary. The type of work I do is primarily "one of a kind" but if I had a very large number of parts to make your soft jaw philosophy would be indeed welcome.

Black Forest
10-09-2011, 09:45 AM
You forget one thing. I don't have a clue what I am doing with machine tools. The soft jaws came with my lathe when I bought it! I don't even know what you are talking about regarding an "adjust tru"!!!!!!!!!

Arthur.Marks
10-09-2011, 12:50 PM
Black Forest - are you being facetious? Adjust-Tru is just Buck's name for having the four screws on the very rear of the chuck OD. They bear on a boss which extends from the backing plate to adjust for small inaccuracies. Personally, I find them a little distracting. They beg to be messed with :) I also wonder what is exchanged for the accuracy they provide. For example, while you're adjusting for concentricity, are you really exchanging axial alignment?

I've decided on the 6-jaw. I can't deny that it is more practical in the long run. The Bison 3-jaw already on the lathe can always be adapted with the "soft" steel replacement jaws. In any event, the ideal method would be the pot chuck/collet. A closer and blank is more affordable than I thought. I can't deny that I still find the Rohm ZSU attractive--if just for the ease of swapping ID/OD jaw position. A 4" is not a 6", though, and it is not such a big trouble to exchange the hard jaw sets. At least, not worth hundreds of dollars!! Haha. Thanks for letting me air my thoughts.

Black Forest
10-09-2011, 01:02 PM
No I wasn't being facetious :)

Arthur.Marks
10-09-2011, 01:28 PM
Haha :D Okay. I hope my explanation made sense then.

DATo
10-10-2011, 07:58 PM
OK Blackie ... I'm sorry. If you got all those soft jaws free with the lathe when you bought it then I retract my criticism. I just assumed you made them.

As Arthur.Marks said, an "Adjust True" is simply a universal chuck, i.e. the kind of chuck where all the jaws move at the same time like a 3 jaw, as opposed to one jaw at a time the way a 4 jaw does. An Adjust True also allows you to fine tune the concentricity by means of adjusting screws on the backplate. So, for instance, you would chuck up your workpiece then indicate it and adjust for the run-out by manipulating the adjustment screws on the backplate. What you are doing, essentially, is adjusting the entire chuck with the fine adjustment as opposed to adjusting one jaw at a time. Normally you don't have to adjust more than a few thousandths of an inch.

Another advantage of the 6 jaw is that it can hold tubing or pipe much more securely without deforming it ... especially thin wall tubing.