Which chuck to buy for first lathe ?

[JAParticipant @ja]

When I answered this question this morning I thought it was a no-brainer. My comment was merely about the dial gauge.

With a three jaw self-centering chuck you can hold round bar with an accuracy dependent on the construction and wear of the chuck. OK you can take precautions or other actions to ensure that your turned surfaces are concentric but you are bound to be bitten sooner or later by the chuck's inherent inability to accurately hold a round bar. It must be said that it can also hold non-round (usually rectangular) objects for facing.

An independent four jaw chuck can be set up to hold round or rectangular bar at a required accuracy. Once mastered, and it is not difficult with a dial gauge, the setting up is not difficult and takes, at the most, a couple of minutes.

I don't understand the faceplate suggestion. The use of a faceplate, I think, is beyond a beginner. It takes some skill and quite a bit of time to set-up and balance something on a faceplate.

What I don't understand is why lathe manufactures and dealers always sell lathes with a three jaw self-centering chuck? OK, it is what the buyer wants (not needs).

JA

[Steve WithnellParticipant @stevewithnell34426]

My call would be a 4 jaw self centering chuck – it will self centre round, square, oval bar and some weird forms (ie Stuart steam governor extrusion). I got one of these years ago and the only thing it can't help with is turning cranks. It is possible to use packing pieces to move the work off-centre, but I've no real experience of doing that.

A minor benefit is that the clamping forces are more even with four jaws rather than three (think about thin wall tube as an example).

There is no "right" answer this – get an independant jaw chuck and have to clock every job and be able to turn off-centre or take the benefit of the 90%+ times you won't need to clock a job but be stumped when you need to turn an eccentric.  I've never been convinced about self centring chuck runouts being a problem.

So it's really back to what you plan to do,  before you buy a second chuck.   In fact I just remembered how to turn cranks in a self centring chuck – l'll see if I can find a picture to upload…

Steve

Edited By Steve Withnell on 06/12/2014 16:31:38

[JasonBModerator @jasonb]

Just read my reply, as Ian says it should have read 3- jaw self centering, was in a rush to get out.

J

[Steve WithnellParticipant @stevewithnell34426]

One method of turning a crank in a self-centering chuck…

http://whittlev8.files.wordpress.com/2011/02/crank-cam.jpg

Steve

[Chris TriceParticipant @christrice43267]

I have two points to make. First is buy a good quality three jaw chuck because if it has a separate backplate, you can fine tune it to hold concentrically like a four jaw. Secondly, and so far not mentioned is convenience and repeatability. If you have twenty or thirty turned items that each need several operations performing on them, the joy of setting a four jaw chuck each time gets stale very, very quickly. That's why most lathes come with three jaw chucks. It's the one most of us use 90 percent of the time.

[Gordon WParticipant @gordonw]

JA – setting a job up on a faceplate is difficult for a beginner, but so is using a 4 jaw chuck. Difference is the faceplate is much cheaper, and you will learn a lot.

[Michael GilliganParticipant @michaelgilligan61133]

Well, Brian: I think you have probably received at least one recommendation for every option.

… not forgetting, of course, that some excellent work can be done 'between centres'.

Let us know what you decide.

MichaelG.

[clivelParticipant @clivel]

I have a Unimat, Basic which is of a comparable size to the Sherline, and like the Sherline can be fitted with either a 4 jaw independent chuck or a 3 jaw self centring chuck. The latter, like with the Sherline, is tightened by means of two tommy bars which are an absolute pain to use.
So if anything, I find that for those of us with only two hands, the 4 jaw chuck is actually easier and faster to use when compared to juggling two tommy bars endowed by gravity with a natural predilection to head straight down into the swarf, and of course two tommy bars are twice as many things to lose and also much harder to find than a 4 jaw chuck key.

Initially when I first got the lathe which was supplied with both chucks I shied away from using the 4 jaw. But after I bough a dial indicator off eBay I decided to give it a try. I soon found that with a little practise especially on these smaller chucks with limited travel, an item can be centred very quickly, and of course the 4 jaw can hold things that would be almost impossible with the three jaw.
My three jaw has long since been relegated to paper weight duty, which has had the beneficial side effect of no more of the scraped knuckles that inevitably occurred, no matter how careful I was, almost every time I tried to open the chuck to remove a piece of work.

Clive

 

Edited By clivel on 06/12/2014 18:53:22

[Capstan SpeakingParticipant @capstanspeaking95294]

Hello folks.

Can I through a little more mud in the water?

I used to use a 4-jaw for holding hot-rolled, forged or cast items to protect the accuracy of a 3-jaw while the rough skin was taken off.

A 3-jaw is for convenience and mounting speed which is far less important in a hobby environment. Also 3-jaws allow for the use of soft jaws which have a myriad of uses in the professional environment.

[Michael GilliganParticipant @michaelgilligan61133]

Excellent points, Clive

MichaelG.

.

P.S. … Straying somewhat from the original topic; these are worth a look !!

 

Edited By Michael Gilligan on 06/12/2014 20:32:22

[Chris TriceParticipant @christrice43267]

Makes you wonder why so many lathes come with a 3 jaw when 4 jaw chucks are generally cheaper? Could it be that for a beginner, they're the better option? It takes about two seconds to grip something in a 3 jaw whereas….

[Brian JohnParticipant @brianjohn93961]

I am a bit confused here : why is the 3 jaw self centering chuck more difficult to use than the 4 jaw self centering chuck ? I would have thought they would both be easy to use : isn't one chuck key enough to tighten up on the work piece ?

NOTE 1 : I have ruled out buying the 4 jaw independent chuck.

NOTE 2 : The 4 jaw self centering chuck is only $40 more than the 3 jaw.

Edited By Brian John on 07/12/2014 02:56:29

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Brian John on 07/12/2014 02:54:29:

NOTE 1 : I have ruled out buying the 4 jaw independent chuck.

.

In that case, Brian … The choice between 3-jaw and 4-jaw self centering chucks is fairly simple.

• The 3-jaw will easily and securely hold round and hexagonal material.
• The 4-jaw will easiily an securely hold square material.

Yes, the 4-jaw will probably hold round material, but less reliably than the 3-jaw.

… holding most other sections will require some initiative.

MichaelG.

[Brian JohnParticipant @brianjohn93961]

Aha, that is what I wanted to know. The 4 jaw does not hold round material well so the 3 jaw chuck it is. Thank you.

[JasonBModerator @jasonb]

Posted by Brian John on 07/12/2014 02:54:29:

I am a bit confused here : why is the 3 jaw self centering chuck more difficult to use than the 4 jaw self centering chuck ? I would have thought they would both be easy to use : isn't one chuck key enough to tighten up on the work piece ?

NOTE 1 : I have ruled out buying the 4 jaw independent chuck.

NOTE 2 : The 4 jaw self centering chuck is only $40 more than the 3 jaw.

Edited By Brian John on 07/12/2014 02:56:29

Brian, its not the selfcentering 4-jaw that is more difficult to use it is the 4-jaw independant. as you have to make small adjustments to each of the 4 jaws in turn until you get the work running true.

To start with I would suggest you rule out the 4-jaw SELF CENTERING, then make your choice between 3-jaw self centre or 4-jaw independant.

My choice would be the package they do that includes the 3-jaw self ctr chuck

[Michael HornerParticipant @michaelhorner54327]

Posted by Michael Gilligan on 07/12/2014 04:14:43:

Posted by Brian John on 07/12/2014 02:54:29:

NOTE 1 : I have ruled out buying the 4 jaw independent chuck.

.

In that case, Brian … The choice between 3-jaw and 4-jaw self centering chucks is fairly simple.

• The 3-jaw will easily and securely hold round and hexagonal material.
• The 4-jaw will easiily an securely hold square material.

Yes, the 4-jaw will probably hold round material, but less reliably than the 3-jaw.

… holding most other sections will require some initiative.

MichaelG.

Hi Michael

Why won't a 4 jaw chuck hold round material as well as a 3 jaw?

I seem to rememeber that clever chap in the US who made the laser centering device for the mill spindle has a website, someone posted a link and I had a look. One of the things he said was that he preferred a 4 jaw independant over the 3 jaw indepandent because it would grip round, hex and square bar.

Grey matter could be off, it's not doing very well at the moment

Cheers Michael.

[Neil WyattModerator @neilwyatt]

A three-point hold will grip firmly at all three points.

A four point grip will only be the same at all four points if the material is perfectly square or round and the chuck is perfect.

In practice there's enough elasticity in the setup that a 4-jaw self-centring will hold round bar, but imperfect square bar may be out enough to cause a challenge for it.

Now would photographers be arguing a four legged camera stand with individually adjustable legs is easier to use than a fixed tripod on a flat floor…?

Neil

[Ian S CParticipant @iansc]

I'd like a little 3 jaw chuck for my Super Adept, the 4 jaw chuck is quite fiddly to work with at this size.

With Chinese, and Taiwanese lathes in NZ it is usual to get one of each 3 and 4 jaw, but when a friend got his lathe home, and opened the box he found 2 of each, and 2 face plates.

Ian S C

[NJHParticipant @njh]

| "Now would photographers be arguing a four legged camera stand with individually adjustable legs is easier to use than a fixed tripod on a flat floor…? "

Great analogy Neil – I can see why they made you the "head – hitter" !

( Bloomin' "return to go" on carriage return still not fixed !!******!!)

Norman

PS Also over enthusiastic spellchecker changed my "carriage return" to "marriage return" – fraught with danger I fear!

Edited By NJH on 07/12/2014 10:27:03

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Michael Horner on 07/12/2014 09:27:20:

Posted by Michael Gilligan on 07/12/2014 04:14:43:

Posted by Brian John on 07/12/2014 02:54:29:

NOTE 1 : I have ruled out buying the 4 jaw independent chuck.

.

In that case, Brian … The choice between 3-jaw and 4-jaw self centering chucks is fairly simple.

• The 3-jaw will easily and securely hold round and hexagonal material.
• The 4-jaw will easiily an securely hold square material.

Yes, the 4-jaw will probably hold round material, but less reliably than the 3-jaw.

… holding most other sections will require some initiative.

MichaelG.

Hi Michael

Why won't a 4 jaw chuck hold round material as well as a 3 jaw?

I seem to rememeber that clever chap in the US who made the laser centering device for the mill spindle has a website, someone posted a link and I had a look. One of the things he said was that he preferred a 4 jaw independant over the 3 jaw indepandent because it would grip round, hex and square bar.

Grey matter could be off, it's not doing very well at the moment

Cheers Michael.

.

Michael,

I think Neil has probably answered most of this on my behalf, but here goes …

• Brian has already ruled out the 4-jaw independent
• I was therefore talking explicitly about 3-jaw vs 4-jaw self-centering.
• For your homework, today read about kinematics …
• why do photographers and surveyors use Tripods?, and why does a milking stool have three legs?
• Extrude that point contact in the Z-axis and you have three lines
• At the limiting condition; when real surfaces meet, there is only ever three point contact … anything more will involve [perhaps microscopic] distortion of surface[s].

Now, translating all of this to the self-centering chuck question: The 4-jaw will grip round stock less reliably for the same reason that a four-legged chair might wobble on a floor [whereas the three-legged stool will never do so].

The independent 4-jaw is, of course, a different matter.

And, by the way; the 3-jaw self-centering will grip any shape … provided that it has constant cross section along the length … it's just that the centre will be wherever it falls naturally.

Hope that makes sense … happy to discuss further, either here or by P.M.

MichaelG.

[Neil WyattModerator @neilwyatt]

Hi Ian,

It will have to be lever scroll to be short enough to allow the jaws can expand into the gap.

Problem with small screw fit chucks is that a short screwed adaptor might be too thin, so an overhung design would be needed.

But, I've got a 2 5/8" lever scroll chuck that's a good fit with the adept. It has a three-screw fitting rather than being screw on. I've made a backplate, but I can't turn the front of it until the adept is up and running.

Neil

[BazyleParticipant @bazyle]

off topic but useful education:

If you put a 4 legged table on rough ground you find 2 legs' in the air'. Try again and the other 2 legs are now in the air. Bother . However a little thought reasons that somewhere beteween those two places is a transition point as it goes from one pair to the other pair and all 4 are firmly in contact . I never have a problem with getting a 4 legged table stable on rough ground.

[roy entwistleParticipant @royentwistle24699]

Hi All Did anyone ever make a three jaw independant chuck?

Roy

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Bazyle on 07/12/2014 11:38:31:

… However a little thought reasons that somewhere beteween those two places is a transition point as it goes from one pair to the other pair and all 4 are firmly in contact .

.

I bet you can stand a sharp pencil on its point, too

MichaelG.

[NJHParticipant @njh]

Roy

"Did anyone ever make a three jaw independant chuck?"

Yes – after a fashion. This is the "Griptru" chuck which allows micro adjustment of the position of the chuck on its backplate. Another "nice to have" – I picked up a S/H one in good condition and it does have its uses – but I would have to think carefully about paying full price for one!

Norman

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