Author Topic: 4 jaw self centering versus individual jaw adjustable type chuck  (Read 762 times)

Offline Reggleston

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4 jaw self centering versus individual jaw adjustable type chuck
« on: February 24, 2019, 09:02:43 PM »
Just curious as to what experience has been with the self centering 4 jaw versus the conventional individual jaw adjustable type. Most of my 4 jaw work involves irregular shaped and off center workpieces like cylinder castings and eccentrics. Not familiar as to how the self centering 4 jaw chucks are set up as I have never owned one. If they are like a 3 jaw self centering you can't do anything with irregular shape. Considering  purchasing of a 4 jaw chuck for my SC4 lathe. Any opinions and experience with both would be appreciated.
Regards.
Bob

Offline derekwarner_decoy

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Re: 4 jaw self centering versus individual jaw adjustable type chuck
« Reply #1 on: February 24, 2019, 10:44:00 PM »
Bob......I think 4 jaw self centering  lathe chucks were designed by Accountants....... :headscratch:    9/10's of useless for any other than repetition of a 4 sided castings where concentricity was an afterthought [not important]

Could be an ideal gift for any Mother in Law who has her own machine shop who has 400 x 6 meter lengths of square precision EN26 bar stock :lolb:

In the Australian price list, you could get an MT3 x ER 25 Collet set to suit your SC4 machine, for about the same cost as the 100mm capacity 4 jaw self centering chuck

Derek
« Last Edit: February 24, 2019, 11:17:55 PM by derekwarner_decoy »
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Offline Neil-Lickfold

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Re: 4 jaw self centering versus individual jaw adjustable type chuck
« Reply #2 on: February 24, 2019, 10:47:42 PM »
They are like the self centering 3 jaw in that there is no adjustment for each jaw. Great for a quick setup with square or octagonal bar and round stock of course. But not black or out of round stock.  A 3 jaw will still grip well with out of round stock, and that is not so with the 4 jaw self centering chuck's. I have one and use it on square stock , it works very well for it's intended use, but I seldom actually use it.  I only bought it because it was too cheap to let go at a closing down sale
 Mine is the Emco one from Austria.

Offline Jo

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Re: 4 jaw self centering versus individual jaw adjustable type chuck
« Reply #3 on: February 28, 2019, 07:51:41 PM »
4 jaw SC chucks will also hold hex stock... as well as round, square, or octagonal.

A chuck with independent jaws is a different beast than one which has a scroll moving all jaws to the same dimension  ;)

Mine is the Emco one from Austria.

Mine is a Bison chuck and I consider it adequate to use on Mr Silky my Hardinge HLV-H and it gets regular use   ::)

Jo

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Offline Jasonb

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Re: 4 jaw self centering versus individual jaw adjustable type chuck
« Reply #4 on: February 28, 2019, 08:02:07 PM »
If you only have a 3-jaw at the moment then the independent 4-jaw would be the better buy as you will get a lot more use out of it.

Online b.lindsey

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Re: 4 jaw self centering versus individual jaw adjustable type chuck
« Reply #5 on: March 01, 2019, 12:47:31 AM »
Go with a 4 jaw independent. As noted it will get far more use.

Bill

Offline Zephyrin

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Re: 4 jaw self centering versus individual jaw adjustable type chuck
« Reply #6 on: March 01, 2019, 09:08:56 AM »
A self centering 4 jaws chuck is very useful for modelling "bar stock" engines. not only for square bars, With some spacers, lot of rectangular stock are immediately centred as required.

Offline john mills

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Re: 4 jaw self centering versus individual jaw adjustable type chuck
« Reply #7 on: March 01, 2019, 09:43:16 AM »
the main chucks for a lathe  is either a three jaw self centering or a four jaw  independent  the 3 jaw will grip well on a lot of bar or items that have been machined the four jaw independent for all sorts of shapes ,castings.and will grip the most even on round   often big lathes will only have the 4 jaw set up and it is used for every thing .
Butt a 4jaw self entering is more of an extra if you are using material that suits,but it does not always grip well the first 2 jaws to come tight might be the only ones that are .The only 4 jaw self centering chucks i used were when i was at tech school over 50 years ago ,they were on old heroes lathes that were old then and those chucks were just about useless did not grip well or run true but that was what was there when the teacher that we had came to that school
but it still comes to when the boss asks what tools do you want you have to ask what work do you won't to do on
your machine and if that is the tool most suited.
     

Offline kev

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Re: 4 jaw self centering versus individual jaw adjustable type chuck
« Reply #8 on: March 01, 2019, 10:09:31 AM »
I use a 4 jaw scroll all the time, it holds all bar stock including hex, its accurate, grips well and if I need to hold off square then I either shim or get the independent 4 jaw out but for all the square bar I buy its very accuratly sized and grips very well

Offline jadge

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Re: 4 jaw self centering versus individual jaw adjustable type chuck
« Reply #9 on: March 01, 2019, 10:18:21 AM »
I don't have scroll 4-jaw chuck, so obviously I don't use one, but neither do I miss one.

On my manual lathe in order of use are a collet chuck (up to 1.5"), an independent 4-jaw chuck and rarely the 3-jaw scroll chuck. I don't use much non-round bar stock, and what I do use tends to be for fasteners, so they get made on the repetition lathe, for which I have a selection of square and hexagon collets. Rather than using non-round bar stock I tend to hog parts out of hot rolled steel. It can be more difficult to get a good finish, but it's cheap, doesn't go banana shaped when you machine it and is less prone to rusting than EN1A.

For me a 4-jaw scroll chuck would just sit on the shelf unused.  :'(

Andrew

Offline Jasonb

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Re: 4 jaw self centering versus individual jaw adjustable type chuck
« Reply #10 on: March 01, 2019, 10:34:22 AM »
Can I ask those who have said a SC 4-jaw is good for holding octagonal stock where they get this from and how often do they use it? In 35 odd years of model engineering I don't think I've seen it sold by any of the hobby suppliers and never had a need to buy any. On the very odd occasion that I may have needed an octagonal head on a part I would just cut from round bar and mill the octagonal feature.

And while I'm her do the jaws tend to mark hex stock as they will only be contacting with the corner of the jaw not a flat face?

Offline Jo

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Re: 4 jaw self centering versus individual jaw adjustable type chuck
« Reply #11 on: March 01, 2019, 11:41:07 AM »
A couple of octagonal parts which were made by holding them in a 4 jaw SC ::) It was a feature on early engines before they realised that there was little point in having more than 6 sides.

I have never noticed any damage but then again parts can be damaged if you over tighten the jaws on any chuck.

Jo
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Offline Jasonb

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Re: 4 jaw self centering versus individual jaw adjustable type chuck
« Reply #12 on: March 01, 2019, 12:09:18 PM »
But did they come out of octagonal stock?

As I said a part like that I would start with round bar - bore, tap and turn the lower round part. Them over to the mill and index the 8 flats before sawing off. The parts could just as easily have been held by the lower round part or screwed onto a make threaded arbor to finish.

The only time I could see a real need for a SC 4-jaw is if doing a lot of work on square bar that won't fit a collect as it saves having to reset the independent as even if you just use the two same jaws on those they never quite go back to the previous position.

Offline kev

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Re: 4 jaw self centering versus individual jaw adjustable type chuck
« Reply #13 on: March 01, 2019, 12:46:33 PM »
Maybe I misunderstand but I think the 4 jaw marks less as the force required to hold the part is distributed over 4 jaws instead of 3 so each jaw needs 3/4 of the pressure that the 3 jaw does per jaw

Offline Jasonb

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Re: 4 jaw self centering versus individual jaw adjustable type chuck
« Reply #14 on: March 01, 2019, 01:25:34 PM »
I was thinking more that when holding hex stock it is the corner of the jaw that makes contact not the narrow FLAT face, could tend to mark aluminium and bronze parts which are quite soft.