Chucks 3 or 4 jaw for general use.

[Billy BeanParticipant @billybean67480]

I found my 3 jaw chuck not running true so bought a 4 jaw independant,

I now happily do my little bits, round or square .

Takes a bit of fiddling with the DTI but works for me.

Would appreciate the thoughts of the more experienced members .

 

Edited By Billy Bean on 02/03/2018 20:08:20

[Billy BeanParticipant @billybean67480]

[Peter G. ShawParticipant @peterg-shaw75338]

Not an expert by any means, but it beats me why lathe suppliers don't include an independant 4 jaw chuck as standard and leave the self-centring 3 jaw chuck as an optional extra. When all said and done, for most work, the 4 jaw independant can do almost everything that the 3 jaw can, the exception being work which is three, six, nine etc sided.

Setting up can be a bit awkward, but depending on what I'm doing, a rough setting using a tool in the toolpost as a guide is sometimes accurate enough: other times, as you say the DTI is required.

Cheers,

Peter G. Shaw

[Nick WheelerParticipant @nickwheeler]

If you’re machining the whole part, what does runout on the chuck matter? Turn all the diameters, part off and worry about something important.

[not done it yetParticipant @notdoneityet]

Even though I have screw-on chucks I don’t change out the 4 jaw independent unless for a particular reason. Doesn’t take long to centre the part and if it doesn’t need to be absolutely spot on, it is no worse than a 3 jaw.

I avoid the 4 jaw self centering chuck unless I am sure the part is perfectlly round (it would only grab on three jaws at best, if stock is not perfectly round) Roughly square in a 4 jaw SC chuck is OK, but concentricity is no better than an equivalent 3 jaw on round stock.

[SillyOldDufferModerator @sillyoldduffer]

If I was only allowed one chuck it would be a 4-jaw. In real-life I make good use of both.

Much depends on what you do with your lathe; it's unwise to generalise. Most of the time I find it quicker to use a 3-jaw and there's no for me reason not to. But I find the 4-jaw is essential for odd shapes and when the nature of the job has me taking the work in and out of the chuck. Even then, it's often possible to reset work in a 3-jaw by marking carefully where it came from and then fine tuning with a dti.

I not a 3-jaw fanboy, quite often I get a run where it's easier to stick with a 4-jaw because swapping isn't worth the effort. The opposite is a mistake. Don't bodge through with a 3-jaw when a job really needs a 4-jaw.

Dave

[Mick B1Participant @mickb1]

I was taught for 6 months full-time at a Government Training Centre in the 70s to use a 4-jaw almost all the time.

When all I had at home was a tiny Unimat 3, I could only afford one chuck so it had to be a 4-jaw.

But laziness has since taken hold. I have a decent 3-jaw and also some soft jaws machined to the diameters I most use. It's not especially easy or quick to change chucks on the Warco WM250V – its only real drawback IMO.

These days I only use the 4-jaw when shape or concentricity requirements leave me no effective option.

[Anonymous]

I almost never use my 3-jaw SC chuck. Although a quality make it is quite worn. Up to 1½" diameter I use a collet chuck. The collets are variable size over a small range and are equally happy holding round and hex. For most larger work I use the 4-jaw independent. It doesn't take long to centre the work. The work is also more securely held, so you can take proper cuts. I also do a quite a lot of faceplate work, especially for castings. I've got two faceplates, a 12" small one and a larger 18" one. The larger one requires the gap piece to be removed.

It helps that my lathe spindle has a Camlock fitting, so it only takes a few seconds to change chucks.

Andrew

[vintagengineerParticipant @vintagengineer]

When I did my apprenticeship we were only allowed to use 4 jaw chucks. 3 jaw chucks were for production work. I can set up a 4 jaw chuck faster than you can set up a 3 jaw chuck with soft jaws. We never used hard jaws except for in the maintenance shop where you just need to do rough work.

[I.M. OUTAHEREParticipant @i-m-outahere]

I wonder if anyone has done a test on the gripping force or jaw pressure of 3 and 4 jaw chucks , i would expect the 4 jaw to be superior in this respect just by the way the closing force is applied directly by a screw and not via a bevel gear and scroll .

If 90% of your work is being machined from round or hexagonal stock and all sufaces are to be turned / faced then parted off the 3 jaw will come out in front but if you have a tendancy to work with odd shaped material which most model engineers do the 4 jaw is well worth the small amount of fiddling around to true up the workpiece , once you learn how to drive a four jaw ( use the grooves in the face and a rule to set the jaws close to the required size and all nice and even ) it becomes a doddle to true up most of the stock you will want to machine .

I use both on my smaller lathe as they are screw on and easy to change but my bigger lathe the chuck is bolted on so i leave the 4 jaw on there .

There is one other thing with a 4 jaw ( independant ) is you can run the jaws as external or internal and mix and match to grip really odd shapes , you dont have to run all as internal or all as external at the same time .

[Perko7Participant @perko7]

+1 to XD351's comments. A friend who is an experienced machinist once told me that i should use the 4-jaw for everything as it grips better and can be made to run true regardless of the condition of the chuck.

[HopperParticipant @hopper]

Posted by Billy Bean on 02/03/2018 20:08:02:

I found my 3 jaw chuck not running true so bought a 4 jaw independant,

How much was it running out by? They all run out by a couple of thou or a bit more. Nature of the beast.

I wouldn't be bothered with the four jaw fiddle for every little job. Definitely worth the money to buy a three jaw as well for me.

Or do what I did and regrind the worn out old Myford chuck to bring it back as good as new. All it takes is a toolpost mounted Dremel grinder and a clover-leaf plate to hold the jaws outwards while grinding the inner surface.

[jimmy bParticipant @jimmyb]

I use a 3 jaw and soft jaws far more than 4 jaw.
Just the nature of the work I do. Thin section and “weak” parts won’t work in a 4 jaw..

Jim

[John OlsenParticipant @johnolsen79199]

I'd have to say I am very impressed with the Burnerd three jaw that my father bought new with the ML7 back in about 1953. Despite all those years of use it is still accurate, perfectly good for all normal work. Of course, if you need absolute concentricity between both ends of the job, you should think about doing the work between centres. I probably use the three jaw the most, but the four jaw gets quite a lot of use too. As does the faceplate for those awkward jobs. I have ER32 and ER 16 colletts too, which are great for round bar jobs.

The skill of machining is not so much about the actual cutting as it is about figuring out how to hold the job, and also the order to do the work in.

John

[Thor 🇳🇴Participant @thor]

I have a small SC 3-jaw TOS chuck and it is used fairly often because it is the most accurate "jawed" chuck (my ER 32 chuck has less runout). For larger work I mainly use the 4-jaw independant or mount it on the faceplate.

Thor

[JasonBModerator @jasonb]

For general use I reach for the 3-jaw if it is round or hex work most of the time and if doing a batch of smaller stuff will fit the 5C chuck. Only use the 4-jaw for irregular and square work or round items that are too big for the 3-jaw. Faceplate only of too large or odd shaped for the 4-jaw to handle. Seems to do the job as many finished working engines would seem to confirm and my prolific rate of production could be down to not spending ages clocking in the 4-jaw for every piece of work.

[steamdaveParticipant @steamdave]

3 jaw Gri-Tru chuck for me for general work, then in order of preference depending on the work:
4 jaw self centring chuck
4 Jaw independent chuck
ER32 collets
Faceplate

Dave
The Emerald Isle

[Anonymous]

Posted by JasonB on 03/03/2018 07:40:36:

…………. as many finished working engines would seem to confirm and my prolific rate of production could be down to not spending ages clocking in the 4-jaw for every piece of work.

Oh dear, another illusion shattered. There was me thinking it might be down to some sort of ability; and instead it's simply down to use of the 3-jaw chuck.

Better dig my 3-jaw chuck out and see if it's salvagable.

Andrew

[MWParticipant @mw27036]

For me, because the centering accuracy seems to be good, the 3 Jaw reigns supreme for general use on the lathe. I would never have the patience to clock every single workpiece on the 4 jaw.

But like others on here, I've got lots of chucks so I'm spoilt for choice and never faced with a "one or the other" scenario. Which of course the 4 jaw would be the only one that could technically hold anything (other than hex). 

But the prolific-ness of the 3 jaw cant be overstated, it's become the "standard" chuck really.

Michael W

Edited By Michael-w on 03/03/2018 12:10:29

[Neil WyattModerator @neilwyatt]

As a large proportion of hobby lathes go to rank beginners, it makes sense to supply a 3 jaw that will meet most of their likely needs, requires no additional equipment to use (without a dti + stand/holder it's questionable is a 4-jaw is more accurate than any 3-jaw) and is also intuitive in its use.

It's also worth bearing in mind that modern, mass-produced 3-jaw chucks are generally not far behind the very expensive ones in performance.

A new lathe with just a 4-jaw is putting an unnecessary set of hurdles in the path of a beginner who, understandably, just wants to get started.

For resetting work accurately the 4-jaw does, of course, come into its own and almost all of use will have one.

For day to day work by a relatively hobby experience machinist, I would argue the best general purpose chuck is down to personal preference and a host of variables (how good your 3-jaw is, how skilled you are a setting work in a 4-jaw and the nature of what you are machining).

In my own case, i generally use a 3-jaw but the main factor deciding which to use is 'can I do this job faster/better with the chuck already fitted to the lathe?'

Neil

[Another JohnSParticipant @anotherjohns]

Hmmm – my 4-jaw SC holds hex just fine.

It depends on what you are machining, isn't it? (if you have more than 1 chuck, that is).

For the last few years, collets and 3-jaw SC, and the odd bit with the 4-jaw SC;I do expect some faceplate work and lots of 4-jaw independent work coming up with some cylinder work from castings.

John.

[MWParticipant @mw27036]

Posted by John Alexander Stewart on 03/03/2018 12:32:52:

Hmmm – my 4-jaw SC holds hex just fine.

John.

What I mean is it wont actually contact all 4 jaws on the faces of the hexagon. Only a 3 or 6 jaw can do that.

Michael W

[Mike PooleParticipant @mikepoole82104]

Why do so many people worry about the accuracy of a 3 jaw self centering chuck? I have never measured the runout on mine or any one I have ever used. I was taught that there is always an error and to plan a job to be machined at one setting in a 3 jaw if concentricity matters. If not possible to machine at one setting then use a 4 jaw independent or machine between centres. If a 3 jaw is wildly out so you can see the error on a part that has been moved then it may need some attention.

Mike

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Michael-w on 03/03/2018 12:36:03:

Posted by John Alexander Stewart on 03/03/2018 12:32:52:

Hmmm – my 4-jaw SC holds hex just fine.

John.

What I mean is it wont actually contact all 4 jaws on the faces of the hexagon. Only a 3 or 6 jaw can do that.

Michael W

.

You might find this previous thread interesting, Michael: **LINK**

http://www.model-engineer.co.uk/forums/postings.asp?p=3&th=102279

… Try the last few posts on the linked page.

MichaelG.

[Another JohnSParticipant @anotherjohns]

Michael W and others – it is not intuitive, but works very well.

We had this discussion at our club a few years ago, and it came up again recently.

Here should be a staged picture I did for our club discussion:

It does work, and there's no issue with the jaws impinging on the sides of the hex.

I'm always trying to learn new things, while trying not to forget things already learnt. Not sure if someone showed me this in my distant past, or that I just had the 4-jaw SC on, and needed to do a quick bit of turning of some hex and lazyness got in the way and…

John.

 

Edited By John Alexander Stewart on 03/03/2018 21:03:31

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