Three jaw vs four jaw lathe chuck ?

E

ebgb68

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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
 
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.
 
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.
 
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
 
Bob you brought up a great point . I'm mostly looking to spin gun barrels and that would be an issue .
 
my vote is for a 4 jaw independent if you already have a 3 jaw scroll.
David
 
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.
 
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
 
Uglydog said:
I wonder if a 4jaw scroll with theoretically hold stock more tightly than a 3jaw.

Daryl
MN
Click to expand...

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.
 
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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