# Three jaw vs four jaw lathe chuck ?



## ebgb68 (Feb 3, 2017)

I've been looking at used chucks and found a couple on Ebay.  A seller has a a four jaw scroll chuck same as a three jaw what advantage or disadvantage would there be in a three to four jaw ?

Thanks Ed


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## Ed ke6bnl (Feb 3, 2017)

they both will hold round stock but the 4 will hold square stock and the 3 will work for 3 sided and hex. Thinking though that a scrolling 4 will not hold rectangular though. Others know a lot more then this newbie.


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## Bob Korves (Feb 3, 2017)

On some level, all round stock is not round.  A four jaw scroll chuck might have trouble with imperfectly round stock, with one pair of jaws being loose -- as I see things, and I have never touched a four jaw scroll chuck so far...  The four jaw would also chuck octagons.  A three jaw scroll chuck will firmly hold imperfectly round stock.


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## Uglydog (Feb 3, 2017)

I wonder if a 4jaw scroll with theoretically hold stock more tightly than a 3jaw.
I like my 4jaw independents.  Never used a 4jaw scroll.

Daryl
MN


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## ebgb68 (Feb 3, 2017)

Bob you brought up a great point . I'm mostly looking to spin gun barrels and that would be an issue .


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## David S (Feb 3, 2017)

my vote is for a 4 jaw independent if you already have a 3 jaw scroll.
David


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## ebgb68 (Feb 3, 2017)

I have a three jaw scroll but it has some miles on it . I have a four jaw independent that I use but its time consuming  to center . A friend has an adjust true three jaw that works great when doing crowns . The four jaw on Ebay already has the D1-4 mount and is in my price range.


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## dontrinko (Feb 3, 2017)

IMO; a 3 jaw centering and a 4 jaw independent. 
  In general a 3 jaw will center round and hex stock close enough for you to do work. A 4 jaw independent will hold almost any shape including round and you can (with a dial indicator) center it with greater accuracy. I see no need for a 4 jaw centering type chuck unless you have a specific need for it. (turning square stock a lot)   Don


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## darkzero (Feb 3, 2017)

Uglydog said:


> I wonder if a 4jaw scroll with theoretically hold stock more tightly than a 3jaw.
> 
> Daryl
> MN



Theoretically no,  4-jaw scroll will not hold tighter than a 3-jaw scroll but it will hold "better". But "better" can mean different things.

The advantages of the 4-jaw scroll over a 3-jaw scroll is similar to the advantages that a 6-jaw scroll has over a 3-jaw scroll but not as great. However there are disadvantages as well. I look at 4-jaw & 6-jaw scroll chucks as secondary chucks to 3-jaw & 4-jaw independents. That is unless you require the benefits from the 4 or 6 jaw scroll chucks more.

I primarily use a 6-jaw chuck cause I like the benefits more for what I do. However when I need the tighter clamping force I'll use the 3-jaw & of course the 4-jaw indi when needed.

I can go on about the advantages & disadvantages of more jaws but the post will get long (unless someone wants). It has been discussed before here.


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## mikey (Feb 3, 2017)

In addition to the typical collection of chuck types, I have a 4 jaw scroll chuck. I agree with Bob that a 4 jaw scroll will theoretically not hold as well as a 3 jaw but I haven't noticed any loosening or greater inaccuracy with it. However, I use it mainly for holding square work that is machined in one go. The main advantage to using it for square work as opposed to an independent 4 jaw is that it self-centers so I don't need to mark a center and hope my drill aligns; I just chuck it and go. As mentioned, unless you do a lot of work with square stock I don't think a 4 jaw scroll chuck is worth the money.

If you have to re-chuck things once its turned then a 4 jaw independent is the best option. I say best because you can get just as close with an adjust-tru type 3 jaw chuck but its going to cost you. Try pricing a Buck or Bison or Pratt Burnerd chuck, then add the cost of a D1-4 backplate and you'll see what I mean. I want one but cannot justify the cost over the already excellent 4 jaw independent chucks I already own.


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## ebgb68 (Feb 3, 2017)

Thanks for the offer darkzero  The Buck with adapter was about 700 shipped .


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## darkzero (Feb 3, 2017)

No problem, I'll go ahead & delete my post.


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## intjonmiller (Feb 4, 2017)

Keep in mind that if you mark your part in one spot, and mark the corresponding jaw of your scroll chuck, then when you need to re-chuck it you make sure to load it the same way again, unless your chuck is in bad shape it should be reasonably repeatable. 

Sure, in theory a 4-jaw scroll chuck will not hold non-round round stock perfectly, but in theory the deformation (always occurs to some extent when chucking) will bring it back into round.


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