# Chucks



## robcas631 (Feb 10, 2013)

What are the advantages of 3/ 4/ or 6 jaw chucks?


----------



## Tin Falcon (Feb 10, 2013)

In most cases 3 jaw and six jaw chucks are scroll chucks the  chuck has a scroll inside that move all jaws in or out together. these chucks typicality have two sets of hard jaws. in larger sizes 8" plus these chucks have one set of hard jaws then soft jaws are screwed to the hard jaws. the soft jaws are machined as needed. 
3 jaw chucks are likely the most common. 6 jaw chucks are used for most of the same uses as a 3 jaw.  the main advantage of a 3 jaw over a 6 jaw is economy . 
easier and cheaper to make. a 6 jaw grips better and applies a more even pressure is good for holding tube and pipe. 
3 jaw  chucks with soft jaws have a similar advantage over a 3 jaw with hard jaws. 
a 4 jaw is probably the most versatile commonly found in the home shop. the jaws are indipendant and reversible. it will hold square and rectangular shapes. you can offset the work from center. you can use an indicator and set work true to center. 
I have heard it recommended that new guys use only a four jaw for their first year. that way you learn to get good at using it. 
imho most home shops do not need a 6 jaw and they are imho  they are too pricey for a home shop. 

These are general statements there are always exceptions. if you find a bargain on a 6 jaw and it fits your lathe grab it. 

Tin


----------



## vederstein (Feb 10, 2013)

A 3 jaw scroll chuck is usually "good enough" for most projects.  It will allow you to grab on round and hex stock.  Run out can be an issue though.

Most 3 jaw chucks have a run out of .003" or better.  Again, this is usually sufficient, but if you're making a part like a piston, get barstock oversized.  (e.g. don't buy 1" barstock to make a 1.000 piston.  Buy something like 1-1/8" diameter).

A four jaw is most versatile.  With a dial test indicator and two chuck keys, you can get your stock very very close to absolute center.  This is good when working with material like drill rod.  But setting up stock in a four jaw is time consuming.  You get better at it the more you do it.

I've never had a 6 jaw, and they are mostly advertised for evenly holding thin wall tubing.  They can be pricey.

I recently bought and mounted a new 3 jaw for my '37 Sebastian.  I documented my purchase and what I needed to do to mount it  here:

http://www.homemodelenginemachinist.com/f13/new-chuck-making-backing-plate-19967/

...Ved.


----------



## GWRdriver (Feb 10, 2013)

Tin Falcon said:


> I have heard it recommended that new guys use only a four jaw for their first year. that way you learn to get good at using it.


I've never heard this before, but I could certainly agree with it to some extent.  My first mentor spent his entire working life in the tool & die industry and could have had anything he wanted, but for many years chose to use only a 4-jaw chuck at home.  He taught me on that one (for about two years.)  It wasn't a matter of "paying dues" or anything, but rather it was very good training and it doesn't take very long to become good (and fast) at it.  I'm occasionally asked which chuck to get first with a new lathe and my answer is always that if you can only have one chuck (at least for a time) and turn anything but round bar and tube, it MUST be a 4-jaw.


----------



## Tin Falcon (Feb 12, 2013)

It was recommended by Forest Addy in an article in Home shop machinist. 

Also most of the old craftsman /Dunlap 109s that I have seen have only a 4 jaw chuck. 2 reasons 1 versatility. second economy. 
In the 1956  Sears catalog the lathe was 48.50 cash  a four jaw 4 inch  chuck was an additional 8.00 and a 3 jaw was 36.50. and the motor was not included . the average (median income for a man in 1956 was $3600.  or $ 69.0 a week. so you do the math. and as we know the little dunlap was is not that usable a lathe. 
Tin


----------



## robcas631 (Feb 13, 2013)

Thank you very much. I learned a lot from your write up. I'd like to obtain a 4 jaw chuck.


----------



## robcas631 (Feb 13, 2013)

Thank you Ved!


----------



## robcas631 (Feb 13, 2013)

Also, one can work on square stock. TY Harry!


----------



## Cogsy (Feb 14, 2013)

Being fairly new to machining, I started with the 3 jaw as supplied on my mini-lathe, but ordered a 4 jaw when I realised I wanted to try offset turning. It sat on the bench for quite a while (I didn't end up doing the offset I was planning) but then, for a reason I forget, I needed it and installed it on the lathe.

It was tricky to set up the first couple of workpieces, especially as I only use 1 chuck key, but got easier as I got used to it. Now I can eyeball a piece to around 10-15 thou, then use a dial indicator to get within 1-2 thou, all within probably 90 seconds or so. If I need to, I can get pretty close to spot-on with a bit more time.

I've never reinstalled the 3 jaw and I can't see a reason for doing so at this point. I love my 4 jaw!


----------



## rcfreak177 (Feb 14, 2013)

Tin Falcon said:


> I have heard it recommended that new guys use only a four jaw for their first year. that way you learn to get good at using it.
> 
> 
> Tin



I was trained to use both 3 jaw and 4 jaw chucks. When the boss saw a 3 jaw on my machine I would be told to put the 4 jaw back up, then got a clip in the ear. Was trained by an Englishman who worked for British Aerospace for years before coming to Australia. (He was as mad as a cut snake but a very good machinist, I was lucky to learn from him)
For some crazy reason I use the 4 jaw 98% of the time on my lathe, I can set the part up faster than in a 3 jaw, holds the part better due to more even clamping pressure, also I believe that beating the part with a mallet while mounted in a 3 jaw chuck to get it to run concentric is bad for the 
head-stock bearings.

This is my only opinion, although others may differ.

Never seen a 6 jaw chuck in my life, not common here in Australia, can see the logic behind them though.

Basically the only time a 3 jaw chuck is fitted to my machine is to spin up hex bar.

Baz.


----------



## rcfreak177 (Feb 14, 2013)

Tin Falcon said:


> I have heard it recommended that new guys use only a four jaw for their first year. that way you learn to get good at using it.
> 
> 
> Tin



I was trained to use both 3 jaw and 4 jaw chucks.
For some crazy reason I use the 4 jaw 98% of the time on my lathe, I can set the part up faster than in a 3 jaw, holds the part better due to more even clamping pressure, also I believe that beating the part with a mallet while mounted in a 3 jaw chuck to get it to run concentric is bad for the 
head-stock bearings.

I was trained by this crazy Englishman who worked for British Aerospace for years before coming to Australia.
Whenever he saw a 3 jaw on my lathe I would get a clip in the ear and then be ordered to fit the 4 jaw back on.
This guy was as mad as a cut snake but I was very lucky to be trained by him and gave my up-most respect back.

This is my only opinion, although others may differ.

Never seen a 6 jaw chuck in my life, not common here in Australia, can see the logic behind them though.

Basically the only time a 3 jaw chuck is fitted to my machine is to spin up hex bar. I can still feel the pain in my ear 

Baz.


----------



## chucketn (Feb 14, 2013)

I was looking for a 4 jaw chuck years ago on e-bay. I bid on and won a 4" 4 jaw for a reasonable price. Imagine my surprise when I received it and discovered in my haste and inexperience I had purchased a self-centering 4 jaw scroll chuck, not an independent 4 jaw (no wonder the price was good!). I didn't know 4 jaw self-centering even existed!
It came with 2 sets of jaws, inner and outer, like the OEM 3" 3 jaw that came with my lathe. The inner jaws were not a correct set and would not close to zero. The seller and I went round and round exchanging emails over the problem  until I photographed the scroll teeth cut in the jaws to prove the set was defective. He finally exchanged the set for one from another chuck and they work fine. It is my go to chuck for stuff that is too big for the OEM 3" 3 jaw and is used just as much. I later used my hard won chuck education to buy an older 4" 4 jaw independent chuck.

Chuck


----------



## Mbusha (Feb 14, 2013)

I knew enough (just barely) to order the four jaw with my mini lathe. First project was an adapter for the mill's rotary table. Goes back and forth often and is very useful. Also, in addition to the four jaw, a face plate is handy as well. 

--Mark


----------



## Coilmotorworks (Mar 14, 2013)

My advice, if you don't already have them, is to Invest in a Last Word style indicator and a magnetic base and dial indicator to aid in centering parts in your newly acquired I4J.


----------



## Mbusha (Mar 14, 2013)

Coilmotorworks said:


> My advice, if you don't already have them, is to Invest in a Last Word style indicator and a magnetic base and dial indicator to aid in centering parts in your newly acquired I4J.



Interapid IMHO, Last Word just does not have enough travel. I have both; with several Interapid and they have always been my favorite. I do have a nice B&S with a black face and orange dial, very cool. It was a gift from the VP of manufacturing for help on a project. Very knowledgable old guy, when I use it I think of him. Funny how some tools in my box make me have memories of the old days.

I'm getting morose, carry on.


----------



## Coilmotorworks (Mar 17, 2013)

I find that I can dial in the part in an Ind. 4 jaw by eye to the point where the travel in the last word is more than enough to finish centering the part. I like the last word because it can be held in the chuck on the tail stock. For those that are new to the thought of using the ind. 4 jaw chucks, with time you can almost center it without the aid of any measuring device with practice. 

There is a the set-true type three jaw scroll chuck. It is a scroll chuck mounted to a back plate that allows for the whole chuck to move for aligning it to center, usually with set screws.


----------

