# How big should a 4 jaw chuck be?



## safarihunter (Jan 8, 2014)

I have a Bison 4 jaw chuck and a South Bend 10" lathe.  The chuck is 8" across and seems quite large on the lathe.  Is that the correct size chuck for the lathe?

Thank you,

john


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## dpat (Jan 8, 2014)

did not know there was a odessa in wash.  
  smart a $$ answer to your ??  1" in dia. larger than the biggest job for the lathe:roflmao:


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## stevecmo (Jan 8, 2014)

I believe 10" SB's typically came with 6" chucks.......Some With 5" three jaw.  Eight inch is a little too heavy for every day use......... Okay for occasional use I would think.

Steve


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## Pacer (Jan 8, 2014)

An 8" chuck is wasted on a 10" lathe - if you run the jaws out very much at all they will hit the bed negating the size of the chuck. Same with a 3 jaw on lathes, sure a big chuck may mount and go round and round, but if a very large piece is chucked up the jaws will hit the bed. Thats why SB used a lot of 5" 3 jaws and 8" 4 jaws on their lathes.


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## fastback (Jan 8, 2014)

I use a 6-inch 3 and 4 jaw on my heavy ten.  The are times when I would prefer a 5-inch 3-jaw.  I do use 5C collets when working with smaller stock.

In my opinion the 8-inch jaw is too big for a 10 inch lathe.

Paul


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## schor (Jan 9, 2014)

5-6" 4jaw is the most you really want to use on a 10" lathe. 8" is doable if that's all you have and fits the work your doing.


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## Bill Gruby (Jan 9, 2014)

I respectfully disagree with all of you. I have had an 8" Cushman 4-jaw in my 9X20 for a while now and never run into a problem.


 "Billy G"  :allgood:


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## samthedog (Jan 9, 2014)

I don't understand why the size is such an issue. If you have the outside jaws for the chuck then clearance won't be a problem.

Paul.


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## fastback (Jan 9, 2014)

To me it is more related to weight than anything else.  Smaller lathes have smaller spindles and bearings.  They are only designed for so much weight period.  If one decides to go with larger then designed it is that person's choice.  It is kind of like rabbit hunting with a 50 caliber gun.  Yes, it will definitely so the job but seems to me its a lot of over kill (pun intended). It also can not be used to its full potential. Not only that but it cost more.  I think an 8-inch chuck is fine on a 12 inch.  

Bottom line is, go with what you want to but larger does not mean it will be any better.  That's my 2 cents (might not even be worth that).

Paul


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## Bill Gruby (Jan 9, 2014)

One thing to remember here is the fact that regardless of the chuck size, the jaws holding a certain part will be in the same position. I use the 8" 4-jaw to stabilize at its outermost hold. especially if I am holding with just one jaw reversed from the others. This set-up has three out and one in.

 "Billy G"


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## 4GSR (Jan 9, 2014)

My 9" SBL has a 8" light duty 4-jaw chuck on it.  Its the only one that I've ever used on it in 40 years.  I have a 6" Cushman for a backup, but never used it.


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## swoop_g (Jan 11, 2014)

I'm glad this question has been asked.  I have an old 11" South Bend and I am in the market for a good 4-jaw at the moment.  I have had problems finding one as my spindle has the odd-ball size of 1 5/8-8tpi so I have been thinking I would have to make a backing plate to mount a new chuck.  But this past week I actually found what the post called a faceplate but it is actually a back plate for a chuck in 1 5/8-8, and it looks like it is in really good shape.  So I have been debating on whether to get a 6 or an 8" 4-jaw.  My current 3-jaw measures 6 1/4" and it looks like I have 2 1/2 - 3" of clearance between the chuck and the ways.  I think I will look for a light-medium duty 8" 4-jaw chuck and see how it works.


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## Bill Gruby (Jan 11, 2014)

Swoop --- 8 inch for an 11 inch lathe IMHO is a good choice. 6 inch would be small, again IMHO.

 "Billy G"


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## drsorey (Jan 11, 2014)

newbe opinion
I have a 6 " three jaw that lacks the backward gripping jaws, a 6 inch four jaw (enco brand).  I recently traded for a 8 inch Bison three jaw.  My heavy 10 flat belt will squeal a little at start up with the heavier 6 inch four jaw.  I intend to use the larger 3 jaw bison only when I need the extra grab or the backward jaws.  I ran the 6 inch four jaw on a HF 9 x 20 lathe for several years, only giving the chuck a little starting spin with no problem.  The South bend is a thousand fold larger and stronger then the 9 x 20, so I am not expecting any trouble.


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## woodtickgreg (Jan 11, 2014)

I have a heavy ten. I do have a 8" 4 jaw that I run on it. I turn mostly small parts with it but if I turn larger stuff I would be very careful and make sure the jaws clear if they extend beyond the chuck body. I use the big 8" because I got what I thought was a good deal on it, less than $100 brand new and still packed in shipping grease. She spun right on and all I had to do was make a skim cut to true up the backing plate. I did a bad video with it on the lathe recently and you can see it running. My 3 jaw is a 6"
I kinda like the mass of the 8" I can run the lathe all day with that big chuck on and the bearings and caps never even get warm. I run a serpentine belt on mine and she starts right up and doesn't squeel. The 3/4 hp motor on my lathe turns it and runs just fine. I am using the original 3 phase motor with a vfd.
Here's the you tube video url
http://youtu.be/C1JodtCfdjA


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## ScrapMetal (Jan 12, 2014)

Bill Gruby said:


> Swoop --- 8 inch for an 11 inch lathe IMHO is a good choice. 6 inch would be small, again IMHO.
> 
> "Billy G"



The 6" on my SB 11" feels a bit small, yet an 8" feels slightly big.  I don't see too many 7" chucks which I think would be "just right". :biggrin:

-Ron


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## samthedog (Jan 12, 2014)

I don't think the 8 inch will be any problem for the bearings to handle. If you have ever taken out a car or trailer's axle, you may be surprised how small the bearings are. These take a great deal more shock than those on a lathe and if they become damaged or worn, you will instantly feel it through the car - though despite this hard life, they last a long time.

The spindle bearings on most lathes are quite large in comparison to the example above and the loads are quite small. The only time the load becomes an issue would be if you are turning a very unbalanced piece, which I believe isn't particularly wise or recommended at speeds that would place the bearings under damaging stress.

Paul.

PS. just noticed the new post icons. Nice


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## swoop_g (Jan 16, 2014)

Bill and Ron- Thanks for your input, I appreciate it.  I know my 6" 3-jaw chuck just feels right and it looks like it has plenty of room underneath.  I got that backing plate yesterday and guess what, it doesn't fit right!  I think at one time it was threaded 1 5/8-8 but it has seen some use.  I tried to run a tap through it just to clean the threads and see how it fit but my tap nearly fell straight through it!  I tried to put it on the lathe anyway to see what it looks like and it has quite a bit of slop in all 6 degrees of freedom.  The only way this can be salvaged is to bore it out and re-sleeve it, something I sure as hell did not plan on or want to do.  I got the plate for dirt cheap so I guess I got what I paid for!  Oh well I'm gonna go make some chips...


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