Set-True and 2 Jaw chucks

[ddmunroe]

Hello
With the set-true three jaw chuck what are the real advantages over a four jaw ?
When would you need to use a 2 jaw chuck ... advantages ?
Input appreciated )
dd

 

[chips&more]

Typically a three jaw has a scroll so one key hole can move all the jaws. A 4 jaw typically has independent jaws. Need to position each jaw separately. A 3 jaw with set-true is the best...self-explanatory.
I can’t recall the job details but I do remember using the 2 jaw chuck idea (4 jaw with 2 removed). It was not a safe thing to do. The part did not hold fast in only 2 jaws…Good Luck.

 

[ddmunroe]

Typically a three jaw has a scroll so one key hole can move all the jaws. A 4 jaw typically has independent jaws. Need to position each jaw separately. A 3 jaw with set-true is the best...self-explanatory.
I can’t recall the job details but I do remember using the 2 jaw chuck idea (4 jaw with 2 removed). It was not a safe thing to do. The part did not hold fast in only 2 jaws…Good Luck.

2 jaw chuck and set-true chuck
When would you need to use a 2 jaw
What are the advantages of a set-true over a 4 jaw
Input appreciated
dd

 

[eweissman]

i used a buck set-tru chuck at a machine shop i used to work at. set tru 3 jaw was better for fine tuning, you dont get too much offset on them, at least not that one..
i dont thing the clearance is more than .020 or so, so if you really needed to offset something, like to bore an offset hole in a rectangular part on the lathe, the fourjaw
would be better. 3 jaw set tru was quicker to set up than the 4 jaw in my experience , but that might just be user preference. most 3 jaw chucks, even nice ones, wont ever
quite repeat perfectly. some might argue otherwise, but my experience has been that 3 jaw set true was needed for high tolerance work where the part needs to be removed from
the chuck for second op. i used a two jaw a few times at that shop, i think the only time we used it was to machine an oval shaped cast part using a custom jaw fixture for that
part. not sure what the advantage was apart from speed of set-up vs a 4 jaw for the same part.

 

[Bill C.]

Hello
With the set-true three jaw chuck what are the real advantages over a four jaw ?
When would you need to use a 2 jaw chuck ... advantages ?
Input appreciated )
dd

Two jaw chucks could be used for production. The jaws could be bored to fit a part that needs a secondary operation. Sometimes movable jaws are mounted on a face-plate for the same reason. Three jaw chucks will have a slight run-out of a couple of thousands. If you turn all the diameters on a piece of oversize stock they are great. Four jaw chucks, if you need to re-machine a part. With the right indicator one can hold one ten-thousand on a hole location. Four jaw chuck take longer to setup but they can't be beat.