PDA

View Full Version : Can anyone explain non-independent 4-jaw lathe chucks to me?



gellfex
04-09-2016, 07:42 PM
Can someone explain how non-independent 4-jaw lathe chucks are useful if any eccentricity in the stock leaves only 2 jaws tight and the other axis loose? I don't get it. Where are these advantageous over 3 jaw or independent 4 jaw?

Toolguy
04-09-2016, 07:55 PM
I like them for milling more than lathe. I use them flat on the table facing up for longer round or square parts on end or on the rotary table in vertical mode with the part parallel to the mill table. I have never had a problem with only 2 jaws tight. They work fine for me. It is a fast way to do multiples of the same part because you only indicate it in for the 1st part, then it repeats for all the rest. i think they hold tighter with 2 opposing jaws than a 3 jaw with jaw opposing air and way quicker and easier than an independent 4 jaw.

10KPete
04-09-2016, 08:07 PM
Not everything that goes in a lathe is round. A lot of work is square.

Pete

chipmaker4130
04-09-2016, 08:17 PM
Not everything that goes in a lathe is round. A lot of work is square.

Pete

That is the problem! If the stock isn't a perfect square, but the chuck is 'right on', one set of opposing jaws won't tighten. Same issue as with a 3-legged stool and one with 4 legs, either one on an uneven floor. Three will not rock, four will. Odds are very good that you'll need to singly adjust one jaw of a scroll-type 4-jaw chuck with every variation of stock or part. Then, when the scroll wears, it won't latch on to perfectly round or square stock either without a similar adjustment.

I think they are intended to be 'set up' for each job and then working multiple identical, odd shaped parts, or the same part in and out of the chuck. I'm not aware of any other advantage.

danlb
04-09-2016, 09:13 PM
That is the problem! If the stock isn't a perfect square, but the chuck is 'right on', one set of opposing jaws won't tighten.

Then think of it as being like a vice. If only 2 jaws are in firm contact, then it's still making better contact than 3 jaw. A 3 jaw chuck will make contact with the middle of side one, and at the corners of side 2-3 and corner 4-3. It will be unbalanced.

A rectangular piece is not a good choice for a 4 jaw scroll chuck on a lathe. :)

Dan

Rich Carlstedt
04-09-2016, 09:15 PM
Not intended for non-symmetrical stock !
Mostly used for square stock and tubing
It allows rapid workpiece changes with such material
More jaws cause less distortion of the work and result in less marking.
You would not chuck square stock in a 3 jaw, and should not chuck uneven stock in a
non-adjustable "Universal 4 jaw" chuck

Rich

gellfex
04-09-2016, 09:24 PM
So far, the only argument "for" the scroll 4-jaw seems to be it's faster to change reasonably accurate square stock than an independent 4-jaw. Seems a stretch. In the latter I simply designate and mark 2 jaws to loosen and tighten while changing stock after I've indicated it.

janvanruth
04-09-2016, 09:56 PM
imagine having to do simple,one off, work at consecutively: round 2 inch, square 2.5 inch, round 1.25 inch, square 1 inch.
Now you take your independent 4 jaw and i will take the scroll 4 jaw.
Guess who will be finished first.

J Tiers
04-09-2016, 10:06 PM
Never seen one of those. All the ones of the type I have seen have BOTH. A scroll, AND independent adjustment. That way you set up as 4 jaw, and then every time you put a new piece in, you use the scroll. Acts like an adjust tru, but has a lot more range, and can hold round, square and irregular (OK not so good on triangular or 6 side).

Doozer
04-09-2016, 10:36 PM
Use them to hold taps.

-D

PStechPaul
04-09-2016, 11:34 PM
When I first bought my 9x20 lathe, I realized that I needed a 4-jaw chuck, so I bought an 8" 4-jaw scroll chuck. and an 8" adapter plate. But there were problems. (1) an 8" chuck really does not fit well on a lathe with 9" diameter swing, (2) it was useless for rectangular stock, and (3) the adapter plate was not made for a screw-on spindle as I had. I really didn't know enough to realize my mistakes. So I traded the new 8" scroll chuck for a 6" Cushman independent chuck that needed repair, bought and machined the proper adapter plate, and traded my 8" backing plate for other things I could use.

http://enginuitysystems.com/pix/tools/Lathe_Chuck_8in_0959_800p.jpg

http://enginuitysystems.com/pix/tools/Chuck_6in_0970_800p.jpg

CalM
04-09-2016, 11:45 PM
I would take a four jaw scroll chuck if it were given to me, but I wouldn't go buy one unless a job using square or octagonal stock came my way. And even then, in the smaller sizes, I might look at 5C collets, or machined soft jaws on the 3 jaw before hunting up and mounting a 4J self centering chuck.

Arcane
04-09-2016, 11:46 PM
I have a 4 jaw scroll chuck that I often use on square stock and occasionally on round stock. Strangely enough I have never had any stock come flying out of the jaws, not even once, and the finished turning was exactly what I wanted it to be. How amazing is that!?

lakeside53
04-10-2016, 12:27 AM
I have one of the scroll+independent. Fabulous... my favorite chuck.

Forrest Addy
04-10-2016, 07:19 AM
All lathe spindle tooling has a purpose, a niche in which it performs particularly well. Scroll chucks, independent chucks, collets, dead centess, pots, spuds, faceplates, etc each with their particular purpose and some nearly universal.

If your work load is mostly round and you never need to work to close tolerances, or never need to get a death grip on a work item for heavy roughing, or never need to grip odd shaped parts you'll probably chances are you'll never need a four jaw chuck.

Four jaws chucks do have their place. They really are universal, grip better, and can be dialed into whatever degree of concentricity the job warrants. If you ever have to work in a manual machine tool job shop where you're expected to run large lathes and vertical boring mills, you better be able to work with four jaw independent chucks.

Tak a look at this video:

https://www.youtube.com/watch?v=0IStp69jcJU

where Adam Booth dials in round work on a four jaw chuck is a minute or so. Look at some of Abom79's videos where he runs larger lathes and you'll see a job shop machinist who knows his stuff and makes is boss lots of money - and he does this in part because he's practiced and efficient with a chuck key.

many of you will never need to work up to this standard on a four jaw chuck but knowing the rudiments of it's efficient use is an inescapable qualification for employment in a general or a jobbing machine shop.

My advise is to not declare against using a four jaw chuck until you get a little practice. If you're serious about learning the use of an engine lathe you really do need to skill with the four jaw chuck. If you have the time it's important to learn this new skill in small bite. Work with it until the frustration kicks in then do do something else. Sooner or later will come a breakthrough and dialing in a four jaw suddenly gets easier.

Here's a couple video to get you started. .

https://www.youtube.com/watch?v=HSjQfnXuhEE

https://www.youtube.com/watch?v=aA0suYN72SE

Be patient, these two guys really know their stuff but they are not teachers so they tend to babble about trivialities and wander off the subject. If you want a few other perspectives get on YouTube and type in "indicationg a four jaw chuck." There's tons of stuff including some utter BS

Story: Back in the old days when I was serving my time, us apprentices were rotated two two month tours through the engine lathes. The first tour we had to use four jaw chucks of everything big and small. These were not the tight accurate chucks the better lathe hands used. These chucks dated from Noah's arc and were so loose when you spun them empty the jaws clattered in the clearances like castanets. Worn really didn't matter. After a week or two of hell's kitchen supervision, we got so we could tweak work into a half thou.

As we gained skill were were tested against a watch eventually dialing in a globe valve body to the seat bore and the bonnet flange face. This represented typical work on an engine lathe in a naval ship[yard and there were plenty of valve bodies on hand for the test. It was a tougher job than simply dialing in a hunk of round stock. One pair of jaws gripped the line flanges and the other pair gripped the body. You had to pad the jaws on the line flanges so you didn't make them and you had to be careful not to bend them by muscling the chuck key.

Usual times for experienced lathe hands ran a couple of minutes. Us apprentices were allowed five. You couldn't get it in five try again next week, no blame, no stigma Try til you get it. Took me a couple of tries and I thought I was a hot shot.

We had to dial in round work too as a preliminary but we didn't graduate to three jaw chucks, collets etc until we mastered the four jaw chuck. Over the years people I used to work with would borrow my lathe for some project. Most retired as senior supervisors and bureaucrats. Even after 25 years of pushing paper they could still efficiently dial in a four jaw chuck - much to their surprise and gratification. Dialing in a four jaw chuck must be a life skill like riding a bicycle.

Doozer
04-10-2016, 08:27 AM
I used to run the toolshop for new equipment and plant repair support.
The main lathe was a Nardini 1440. I loved that lathe. I get real excited
when other members post pics of their Nardinis.
Anyhow, production people would often come by to do a quickie job on our
lathe. Cutting off piston caps or opening up wrongly crimped units to
salvage the parts, whatever. Mostly dimrods who left the key in the chuck
and left a mess of chips. The best is when they wanted to use sandpaper
on the lathe. I booted those jokers out of there. I had a brand new hot
shot boss who just jumped on the lathe to do something. He had the lathe
in a low gear, left the key in the chuck, and turned it on. They key stayed
in the chuck, came around, and hit the bed. It luckily broke off the square
of the chuck key. All this coddling of retards had to end.
The plan was to force them to think. They are either too lazy or too stupid
to think, so it worked. What did I do? Replace the scroll chuck on the lathe
with the 4 jaw independent chuck. No one wanted to use my lathe anymore.
I felt it a small victory in a screwed up cooperate system.

-Doozer

CCWKen
04-10-2016, 09:07 AM
A 4-jaw scroll is great for working on thin wall tubing and soft rounds (like brass, aluminum). It spreads the clamping force and you get less distortion and fewer marks.

gellfex
04-10-2016, 12:39 PM
All lathe spindle tooling has a purpose, a niche in which it performs particularly well. Scroll chucks, independent chucks, collets, dead centess, pots, spuds, faceplates, etc each with their particular purpose and some nearly universal.

If your work load is mostly round and you never need to work to close tolerances, or never need to get a death grip on a work item for heavy roughing, or never need to grip odd shaped parts you'll probably chances are you'll never need a four jaw chuck.

four jaws chucks do have their place. They really are universal, grip better, and can be dialed into whatever degree of concentricity the job warrants. If tyou ever have to work in a manual machine tool job shop where you're expected to run large lathes and vertical boring mills, you better be able to work with four jaw independent chucks.



Sorry, but you didn't read my OP. It's about 4J SCROLL chucks, not 4J independents, whose virtues are obvious.

gellfex
04-10-2016, 01:11 PM
A 4-jaw scroll is great for working on thin wall tubing and soft rounds (like brass, aluminum). It spreads the clamping force and you get less distortion and fewer marks.

But not nearly as well as a collet, if it's small enough for your collet range.

wierdscience
04-10-2016, 04:22 PM
I have a 4" 4j scroll chuck for my 9x20.I use it primarily for griping hot and cold rolled square stock when making linkages and rod ends.I also use it for the odd run of square parts both in the lathe and the mill.

It has it's place and given it was less than $100 new it has more than paid for itself in time saved fiddling with a 4j independent.

Forrest Addy
04-10-2016, 04:50 PM
But not nearly as well as a collet, if it's small enough for your collet range.

Yeah, I know, Gel, but I never miss an opportunity for a constructive rant. Sorry if I stepped on your post.

Alistair Hosie
04-10-2016, 05:18 PM
I have a four and a three jaw scroll chucks. I mainly use the four jaw as it gives me no problems and seems (If it is not just in my minds eye) to grip better/stronger. I suppose I got used to them as I am mainly a woodturner /cabinet maker (Hobby level but improving) and all the woodturning chucks seem to be four jaw scroll chucks.So possibly without understanding the physics involved I just assumed and still assume four is better than three. LOL. As said so far it seems to work good for me and I stick with it.
When I bought my lathe it came with a faceplate, and three chucks, one four jaw independent, and one three jaw scroll ,and one four jaw scroll. I have been told a four jaw scroll is quite unusual ,I am not sure if this is correct..
Since it is for fun and relaxation for me, and also gets me out to my little own space where I can truly be as happy as is possible when not inside my home or with my wife family which I also love. Watching t v long term is seriously bad for you IMHO.so the shop is my grown up Disney world.
If that makes sense.
With things as they are ,It is truly wonderful ,that way back over twenty years now, I started to lay plans and have never looked back.
It is a big part of my life now.
I REMEMBER WELL
That Both my father in law, and an elderly friend,way back when I was not quite forty years old ,told me that they had always wanted to have a workshop but both of them added, it's too late for me now, The years went by and they simply left it too late . I was determined not to let that happen to me.Have fun friends .Alistair

Doozer
04-10-2016, 06:31 PM
I have a 4" 4j scroll chuck ..... it has more than paid for itself in time saved fiddling with a 4j independent.

If you call using a 4 jaw independent chuck FIDDLING,
then you evidently don't know how to use the chuck.
From wacked out to half a thou should take a minute.
For repeat parts, much less. People who bash a 4 jaw
independent chuck make it easy to spot the posers
from the real deal.

--Doozer

PStechPaul
04-10-2016, 06:59 PM
Now that I've gotten used to my repaired 4-jaw independent chuck I rather like using it and it usually doesn't take too long to adjust. I have found that I sometimes need to tap the work with a small hammer or the equivalent to get it running true, and then tighten the jaws evenly. Sometimes I don't even use a DTI, but just set the cutter so it just touches the work and leaves a mark on the high spot, and then a very small adjustment gets it right. With the adjusting screw 8 TPI, each turn is 0.125", so it requires less than 1/100 of a turn to move a thousandth. Sometimes a light tap followed by additional tightening does the trick.

I can understand the premise that a 4-jaw scroll chuck might adjust faster and hold tighter than a 3-jaw on round work, but unless the chuck is nearly perfect AND the piece is perfectly round or square, It will really have maximum grip on two opposite jaws while the others just barely touch and keep the work from moving laterally. For tubing there may be enough deflection for fairly equal pressure on all four jaws, and for the same force on each jaw there may be 30% more total gripping force than a 3-jaw.

It's also a good idea to tap the work a little bit on a 3-jaw before final tightening, as it is possible for two jaws to hold the work by friction. And it is a good idea to use all three adjusters on a scroll chuck, and finally on the "master", if so equipped.

Tundra Twin Track
04-10-2016, 08:05 PM
Use them to hold taps.

-D
I use this sliding Tap Holder on Lathe with 4 jaw scroll chuck.

http://i1371.photobucket.com/albums/ag292/tundratwintrack/image.jpg2_zpscnx6fnww.jpg (http://s1371.photobucket.com/user/tundratwintrack/media/image.jpg2_zpscnx6fnww.jpg.html)

Doozer
04-10-2016, 08:59 PM
The 3 jaw vs 4 jaw debate is like the
Testes great, Less filling
beer argument.

-D

gellfex
04-10-2016, 09:05 PM
The 3 jaw vs 4 jaw debate is like the
Testes great, Less filling
beer argument.

-D

Freudian slip?:confused:

I dunno, as I said in the OP, the relative uses of 3 jaw scroll and 4J independent are pretty clear. It's the 4J scroll that puzzles me.

wierdscience
04-10-2016, 09:24 PM
If you call using a 4 jaw independent chuck FIDDLING,
then you evidently don't know how to use the chuck.
From wacked out to half a thou should take a minute.
For repeat parts, much less. People who bash a 4 jaw
independent chuck make it easy to spot the posers
from the real deal.

--Doozer

If you have a 100 parts to produce,each larger than the largest square collet and they need to repeat within .002"you will be fiddling around with two of four jaws on every last one of them.

Unless you have a good 4j scroll chuck that is.

And no I am not a poser.

Doozer
04-10-2016, 09:48 PM
This is Home Shop Machinist.
What are you doing making 100 parts?
-D

wierdscience
04-10-2016, 09:53 PM
Some people finance their home shops in various ways.

CCWKen
04-10-2016, 11:13 PM
I'm wondering how someone poses as a home shop machinist? Or is it a machinist in a home shop? What's the qualifications? I think I are one. :)

Joel
04-11-2016, 12:42 AM
make it easy to spot the posers
from the real deal.
--Doozer

+1 Ken.

And calling Wierdscience a poser is laughable at best. Darin is about as "real" as they get - and one HECK of a nice guy in addition.

Left Handed Spud Wrench
04-11-2016, 01:54 AM
I understand the value of the 4 jaw chuck... I just never bothered to learn it. 3-jaw and collets do what I need them to do.

I suppose I should learn it some day and develop that "knack" with it. I'll put that on the list of things to master when I win the big lottery and can afford to commute to work by SpaceX. "OH %&*(*&! HERE HE COMES! QUICK MOVE ALL OF THE CARS OUT OF THE PARKING LOT -- too late. Call the fire-department."

Puckdropper
04-11-2016, 01:54 AM
If you call using a 4 jaw independent chuck FIDDLING,
then you evidently don't know how to use the chuck.
From wacked out to half a thou should take a minute.
For repeat parts, much less. People who bash a 4 jaw
independent chuck make it easy to spot the posers
from the real deal.

--Doozer

I've heard of one method, to think of the 4-jaw as two 2-jaw chucks and adjust jaws 1 and 3 to center then 2 and 4. What method do you use?

boslab
04-11-2016, 02:45 AM
I have a few 4j independent, I did have a 6j independent that was great for tube, my assertion was clamping load/ no jaws, more jaws, less squeeze. An opinion only!
I'd guess a 4j indipendant as good as a 4j scroll, but slightly slower for repeating random size square work, the same for repeating same size work, better than a 3 jaw every time, you can't clock in a three jaw, unless it's indipendant, and I've never used a 3 jaw indipendant!, I should imagine it would be a pig to set!
Rough and ready is 3 jaw and close work 4 jaw, the more you use a 4 jaw the faster you get at setting it, I can't be bothered to change from a four jaw, takes longer to change the chuck than it does to clock a peice in.
Doesn't matter which jaws you use, so long as your working opposite jaws 1:3, then 2:4, or in my case chalk cross and chalk circle as I can't even see the numbers without glasses and a torch so why bother
Mark

PStechPaul
04-11-2016, 04:38 AM
Has anyone ever put markings and a pointer on the screws of an independent 4-jaw chuck so that you can first roughly set the jaws in 1/8" steps using the rings on the face, and then dial in to within maybe 0.005" with 25 markings? My 4-jaw chuck has rings maybe 1/2" apart which can be used for rough approximation but it would be cool to be able to set it more accurately and quickly before using an indicator for the last 0.005 adjustment.

wierdscience
04-11-2016, 08:49 AM
+1 Ken.

And calling Wierdscience a poser is laughable at best. Darin is about as "real" as they get - and one HECK of a nice guy in addition.

Awh shucks:o:cool:

Jaakko Fagerlund
04-11-2016, 09:57 AM
Has anyone ever put markings and a pointer on the screws of an independent 4-jaw chuck so that you can first roughly set the jaws in 1/8" steps using the rings on the face, and then dial in to within maybe 0.005" with 25 markings? My 4-jaw chuck has rings maybe 1/2" apart which can be used for rough approximation but it would be cool to be able to set it more accurately and quickly before using an indicator for the last 0.005 adjustment.
"Rough" adjustment is by using a vernier from the jaw to the body, then mount your work in it.

Doozer
04-11-2016, 10:00 AM
I never called anyone a "poser".
I said he who complains about a 4 jaw chuck
makes a poser easy to spot.

-D