10 Questions You Should to Know about 3 jaw chuck clamping force

Afternoon,
I'm stuck in the house with a cold/flu, so I've been reading a lot and watching machining videos until my brain starts hurting.
I have what is probably a totally newbie, knows nothing question that popped into my head.
I ended up with both 3 & 4 jaw chucks for my W210 bench lathe.
Most of what I've seen says that the 4 jaw chuck is far superior than the 3 jaw.
Should I just start using the 4 jaw, and save the 3 jaw for some project down the road? Like making a rotary table or dividing head for my mill?
Or are there times when the 3 jaw is preferable?
Thanks for everyone's advice for all my questions. Truthfully, I haven't even started using my machines. The past 6-8 months have been rough. Too many bumps in the road that have had huge impacts on our family. None of them good, unfortunately for us.
Anyway, that's my concerns.
Thoughts on the 2 chuck types?
Thanks,
Ken In my opinion there's a place for both. If you can complete all of your operations without removing the part from the chuck, or its six sided etc., then the three jaw is the way to go, for speed and ease. If you are going to be removing the part from the chuck, or adding a feature to an existing part then being able to dial it in with a four jaw is pretty much a requirement.
If you have both, keep 'em if you can, if you are only going to have one, the four jaw is the most versatile... Usually the 3 jaw is the default chuck as it is quick to use - cannot beat few seconds to load. It is as accurate as 4 jaw if you turn stock down and do not remove it.

The 4 jaw independent is only accurate if it is quality chuck or you ground it - even then do not expect miracles. It is for non round stuff & for stuff where you need to position initially accurately. Also if you take stock in and out. It also places a bit less stress on stock if you want & holds more securely (if you want) vs. 3 jaw.

4 jaw ind. can do almost anything 3 jaw can.

collet chuck - can be quite accurate & fast but for set sizes only (combines 3 & 4 best things but for only certain range). There are many chucks for different collet systems.

soft jaws - if you need "collet chuck" for special size.

6 jaw - mainly for pipes and delicate stuff - but can be used for same stuff as 3 jaw (heck you can remove 3 jaws to make it into a 3 jaw). delicate and easy to break.

all chucks can be "set true".

There is rare 4 jaw non independent as well as 2 jaw chuck.

Face plate is of use for very odd shapes. Dog driver is... to drive a dog.

For thin stuff you can mount a magnetic chuck.

It is true, but counter intuitive, that your 4 jaw should be more expensive then 3 jaw. Generally people have both plus face plate. Hope this helps. It really cones down to a couple if things, Scrolling 3 jaws (or any scrolling chuck for that matter) for accuracy need to be ground on the lathe for accuracy (I've never done mine as I wasn't aware till recently....YouTube).

4 jaw independents (or any independent for that matter), accuracy is controlled by the user, this I knew. Grinding to refresh the grip if needed is good but it does wear out your jaws, so my advice on independent jaw chucks is not to grind unless needed. Watch a few YouTube videos for fastest set up. Typically it takes about me about 2-3 minutes to set up now (less if I'm doing it more often).

I use my 3 jaw mostly as it gives me the results I need, when upping the game I switch to the 4 jaw.

One thing I've noticed is the mistake most make is the chase of infinite precision and not accuracy. Understand what you need as accuracy for your work and not what precision you can get. Most of the work I do never needs precision to the point of worrying about the inaccuracies of a 3jaw chuck. From turning alone, Especially on lighter lathes) holding to .001 takes special care anyway, so the 3J doesn't seem to matter.

+1 to all the advice above.


[edit]

The old school view is that 6J are for pipes... It turns out that that is based on some old school biases from 75 years ago. Many machinists use a 6J because of the better holding. Tom Lipton did a video on this about 4 years ago. Robin Renzetti has made similar comments. and Gotteswinter's old machine had a 6J on it for normal use. I've never heard of a 6J breaking or wearing out prematurely, especially for a hobbyist. I keep the 3 jaw on my lathe most of the time unless I have need for the 4 jaw.
I bought a Bison made in Poland 6" three jaw scroll chuck for my 10K Southbend lathe
back in the mid s. It is a very well made chuck or maybe I got lucky. When I sold
the Southbend and replaced it with a 12"x36" Craftex lathe I kept the Bison chuck and put
the new Craftex chuck on the Southbend. There is a "O" stamped beside one of the pinions
for tightening the jaws that is supposed to be the lowest runout. Chucking a shaft 2" and under
the runout is under .002"

yota

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• May 30,

• #1

this is the 9" 3 jaw on my new to me lathe. it has 3 points to tighten it down. have only used 3 jaws with 1 point. curious about that. but my real question is, what is this mark at one of the tightening points that is not at the other 2? I did determine with a test indicator that when I use the point with the mark, I get a fair amount less runout than with the other 2 points.

mksj

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Many chucks have a master pinion, technically it provides the best consistency to use it when tightening the chuck. Using different ones could cause more variation in TIR. Some chucks only have one pinion for tightening. The arrow or sometime a "O" indicates the master pinion.

yota

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Many chucks have a master pinion, technically it provides the best consistency to use it when tightening the chuck. Using different ones could cause more variation in TIR. Some chucks only have one pinion for tightening. The arrow or sometime a "O" indicates the master pinion.

thanks. then the only reason I can think of to have the other 2, maybe it's best to work your way around and then finish tightening with the master one? wonder if corrections could be made with the other 2 to fine tune runout?

benmychree

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• #4

I know of no reason to "work your way around" in my 60 plus years in the trade, I used the best pinion for concentricity, in fact my Buck Chuck uses only one pinion.

yota

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I know of no reason to "work your way around" in my 60 plus years in the trade, I used the best pinion for concentricity, in fact my Buck Chuck uses only one pinion.

just trying to think of a reason they would spend the time and money to install 3 pinions.

CJ5Dave

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• #6

If I have a part slipping I tighten all three and usually that will secure. Of course my stuff is never the best.

RaisedByWolves

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• May 31,

• #7

just trying to think of a reason they would spend the time and money to install 3 pinions.

So you don't have to hunt to find one.

I hear a lot of talk about tightening all three and whatnot and to me it makes no sense as a 3jaw is not a precision workholding devise in the first place.

OTmachine

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• May 31,

• #8

So you don't have to hunt to find one.

I hear a lot of talk about tightening all three and whatnot and to me it makes no sense as a 3jaw is not a precision workholding devise in the first place.

I am guessing that you have never used a Bison three-jaw, (repeats within .001 t.i.r. every time).

bill stupak

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• May 31,

• #9

Both of my Bisons (5" & 6") repeat to ."