Threading an originally pinned reciever?

[mitch_04]

Hi All,
I just purchased "The Complete Illustrated Guide to Precision Rifle Barrel Fitting", and WOW! It is an amazing book. The first rifle I'm going to "practice" on is a Marlin bolt action 22LR. The book explains how to face a receiver using a mandrel that he explains how to make, however it's for threaded receivers. I plan on threading my receiver, but I'm wondering how to set up the receiver in a lathe to thread it. Can I just set it in the 4 jaw chuck true to the outside of the receiver and use an internal threading tool? I would love to know how others do it, once I get the inside threaded I feel pretty confident in all other aspects of the build. I also have a professional machinist who is supplying the lathe and watching my back. He mainly builds parts for farm equipment (rural town) so he doesn't know much about the rifle side of things. However with my knowledge and his skill we should be able to build a gun that shoots as well as it did before we tore into it!

Thanks,
Mitch

 

[Preacher]

You need to dial in the action with a ground and hardened rod that fits the bolt bore raceway to have the new threads any where close to perfect..
The outer receiver is probably not close to being perfectly centered to the bolt race way.....

 

[mitch_04]

So I make a rod that fits perfectly inside the receiver, then chuck the receiver in the 4 jaw, and indicate off of the rod I put on the inside, correct?

 

[spclark]

Is it practical to indicate off the INSIDE of a receiver for the operation intended?

Seems like a lot of extra work to fabricate then install a "plug" to indicate off of, as well as adding a number of ways to introduce dimensional and/or angular errors.

I am NOT a machinist or metalworker by any stretch... though I can take pride in the results I get from a well-handled file from time to time.

 

[mitch_04]

I would GUESS that going off of the inside of the receiver would be the best because that is where the bolt will line up as well. Then your bolt and barrel are inline. I do understand what you are saying though, something like a basic Marlin probably does not have a perfectly concentric, true center.

Preacher,
Should I pin this "slug" into the receiver to prevent it from slipping, or will it stay in place as long as it is cut as close to the receiver's dimensions as possible?

Thanks for the help everyone,

Mitch

 

[Preacher]

If it is cut to a exact fit you will not need to pin it..
Make sure it is long enough so you can dial in at 2 point on the fitted rod...
Even the inside may be off from the bolt bore raceway, it will be close, but who likes just close when dealing with accuracy..

 

[BoydAllen]

To do it right, you will need to use a setup that is the same as is used for single pointing the threads of a threaded receiver when blueprinting an action, except you will be starting from scratch, cutting new threads. I suggest that you take a look at this page. http://www.bryantcustom.com/articles/true.htm
What you seem to be doing is to reinvent the wheel. For something like this, it is better to copy what is already known to work. Good luck.
BTW a friend has threaded a previously pinned Marlin .22 Mag., replacing the barrel with a high quality match grade stainless one, and chambering it with a match reamer of his own design. It works a lot better now.

 

[mitch_04]

Man I love this website, you guys not only told me exactly what I wanted to know, but also did it without telling me to send it to someone more experienced. I also have a 22 Mag Marlin that was up next if the first goes well. I will probably rebarrel with a Green Mountain for now, they are inexpensive, and my 10/22 GM barrels seem to shoot very well. I put one on my buddies and at 25 yards with a balled up sweatshirt I was able to shoot 3/16" groups. That was with my own trigger job, and a headspaced bolt. My friend works at a large shop with quite a few different machining tools, now I just have to talk him into spending a Sunday working on my gun. Luckily, a case of beer goes a long way these days!

Thanks again everyone,

Mitch