lathe 4 jaw?

[brian923]

i keep reading that you need a four jaw tailstock,i think, i know how to use a lathe, but not the terminology. sorry)
but anyways...to do any action work, or blueprinting. can you do it with a 3 jaw? or is it not good enough? thanks guys, brian

 

[JDJones]

if your planning to chuck up on the action or barrel itself then no the 3 jaw won't give you a "good" job, also note that neither will a 4 jaw scroll chuck or even a precision 6 jaw scrol chuck, the reason is that any "scroll" chucks don't allow the jaws to be moved individualy like a standard common 4 jaw.
Now if you have an action trueing jig,"LIKE" desgine wise, the one that Greg Tannel sells, you can true actions and fit barrels by using it as it allows you to dial in on a 3rd axis just like having a spider on the back your headstock or useing a 4 jaw and a steady rest.
to get a quality job the barrel needs to be setup and indicated off of the bore rather than the outside diameter on the barrel.

I made my own jig out of 5" CM bar stock and my adjustment screws are 5/8" diameter but 28 tpi so its is increadbly rigid and the hole is bored to .0002" od the outside allowing me to thread and chamber barrels using only the jig instead of a spider through the headstock or a steady rest and doing so with the jig chucked up in a 3 jaw scroll chuck, I woulden't reccomend doing this with a standard 4" aluminum jig as I persoanly woulden't trust it not to flex a bit.

 

[brian923]

is there any way that you could send me a puicture of your jig? i think that i know what your talking about, i have a pic in my head, but you know how that goes. thanks a lot for your help, brian.

 

[JDJones]

Greg Tannels jig http://www.gretanrifles.com/actiontruing.asp

 

[JDJones]

I can't get a pic of my jig as its at work and their are no camera's allowed in their. It looks just like the one in the link but a little bigger and beefed up looking and my action bolt are made from bar stock that was single point threaded on the lathe and has a little 3/8 hex head on them.
the reaseon for the fine threads is that when you dialing in an action to a max run out of .0002" it takes very little to move the indicator, in fact I have setup an action at 6 am at around 55 degs and let it sit till noon when the temp got up to the mid 80's and the dials had moved .0008" that put me a full .001" out of my range!!! and thats with a 4140 Steel jig and steel bolts that had been heat treated so I suggest that once you get your action dialed in that you go ahead and make your cuts right then.
I'm not knocking Gregs work but the one jig I saw that was bought from Midway that had his name on it was pretty poorly made, the bolts fit kinda sloppy and the finish was just rough cut, I do like the flat swivel screw caps he has on thei action screws though.

 

[brian923]

thanks JDJones, that looks doable. i appreciate it, brian