GTR or PTG action mandrel/reamer diameter?

B

Brodie

Guest
Hi,
I'm curious what the diameter of these mandrels are. I'd like to make up a bushing set out of brass and my own mandrel but I want to make them so they would work with the PTG/GTR reamer and mandrels. I can't afford the reamer right now(definately a tool I would like to purchase in the future), nor can I justify $35 per bushing for the amount of rifle work I'll be doing.
thanks.
-Brodie
 
Brodie,

I just bought the whole system. The cutting diameter is .705 on mine. The bushing surface diameter is .500. I used some bushings that I made for a piece of 1/2" drill rod I have been using to dial in actions and they worked fine. I think I turned the i.d. of the bushings to .5015-.502. The PTG bushings are nice, but they are expensive. I'm not sure about using brass for the bushings, maybe someone with more knowledge than I will chime in. I know the PTG bushings are hardened and ground.

Hope this helps,
Med.
 
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Med,
thanks for the help. I'll make a .500 mandrel out of cold rolled and my bushings to suite.
-Brodie
 
Hardened steel bushings don't change with use and age...

I have about 9 bushings starting at .7010 going up in 1/2 thou diameters. I also have 2 thou thick shim stock which extends my diameter range for the odd time it is required.
 
Dennis, I agree the PTG hardened/ground bushings are the way to go, but out of my budget. I don't expect alot of wear they won't see alot of use and if it ever gets to that point I will get the PTG bushings.
 
After you make the mandrill, check it closely . Cold rold has a way of
changing . Cold rold steel is full of stress and as your turn it in a lathe
it heats and what should have been straight is now changed. If it is
your purpose to face the action, that alone accomplishes nothing
as the threads may still be off and no doub't not on the same axis
with the receiver face. A 1/2 cold rold mandrill might not be ridgid
enough causing chatter on the face. Without the tap section on your
mandrill, you would have to rely on a set screw which will bend the mandrill.
 
Bob I follow what your saying about the stresses in the cold rolled, very good point, I'll turn one out of regular mild steel.
I just want a mandrel that will ride in the bushings so I can indicate the action in true with the spindle center. Then I'll remove the mandrel and begin trueing the action.....the whole nine yards, single point cutting the action face, threads, lugs.
Am I on the right track here? You guys are dealing with a newb :)
I appreciate the responses.
 
Brodie,

I talked to Dave Kiff about making a hardened mandrel to try to save some money, he quoted me a $100, that is somewhat cheaper. You could buy one and still make your own bushings. I used drill rod for a gun I built for myself as an experiment, the rod had about .008 runout. I just dialed the action in to .008 runout and turned the rod 180 degrees while in the action race and bushings and split the difference to make the runout .004, then turned 180 again and insured the runout was still .004 using a .0001 test indicator. Not the ideal method, but it seemed to work ok. The gun shoots exceptionally well. Now that I have the reamer/mandrel I'm going to ream and redo that action. I'll post the results when I get around to doing it. If at all possible I would opt for something precision ground and hardened. You could actually make the action worse by using something that is not straight or is unstable from not being hardened, at least that is what I have been told as I was getting started in this process. Now, let the beatings begin as to my above method.

Hope this helps,
Med.
 
Med, Dennis , Bob.......thank you for the info, I will just purchase the right stuff from PTG and be done with it. May as well do it right if I'm going to do it at all :)
 
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