Measuring internal Threads

I have no hole to bore I need to thread the outside of the barrel to fit the threaded hole. I don't know how I can get a caliper to read the valleys of the hole thread. I think for the sake of accuracy I'll go with cerrosafe. I already am pretty good at building in variables by accident so I don't want to engineer them in. LOL.
 
I would think you could make a very good copy using hot glue! Apply sometype of release compound first then you could probably place the end of a gluestick into the barrelhole and gently heat the Reciever until the glue softens and flows into the threads. Put in the fridge for a few minutes and it should unscrew right out. I would probably find a way of blocking off the back side so that the glue stays in the threaded area but if that's not possible you should be able to make it work either way.
 
12L14 is pretty inexpensive.
I'd thread as many chunks of that to what I thought it was till I ended up with a good fit.
Then thread the barrel to match your new "thread gauge".
In the few mausers I've done I've run into 4 different thread sizes. A couple of them I think were intended to be the same thread but what the operator put out that day was not on target.
 
Don t use the caliper to measure with but go in with a pre determined size. Set the pc. So its vertical with light coming through the bottom. Set the calipers and rock on the thread with your pre measured and set caliper. Use it like. Go no go guage then go verify with some aluminum.
Lightly oil the thread and lay putty on it. Pull it out and get your pitch and angle of thread. Have at her!
 
I would use an inside micrometer to find the ID. The jaws span the thread peaks and give a better reading. The problem is that you probably don't own one of these contraptions so the next best option, for me anyway, would be to take a piece of round stock and turn it down until it juuust slips into the bore and measure that. We know that production tolerances for threads can be rather coarse so we cannot rely on a standard; using a plug gauge you make would at least get you within a few tenths if you work carefully. Then you'll at least have an idea of what the minor diameter is. Then you can sort out the pitch with a pitch gauge and you'll have your thread.

It's going to be fun sorting out the thread form. I'm not a gun guy but figuring out if they used a 60 degree thread or a 55 degree Whitworth could be challenging to do by eye. Here I think the Cerrosafe stuff might come in handy.
 
I remember reading an article on that stuff(cerrosafe) or some equivalent. The guy was doing something with the receiver of a rifle. Wish I remembered what. Anyways, I think that’s a really good idea. I had the distinct impression from the article that the author was happy with it.
 
It looks to be a 60 degree thread. And I now forget what pitch I thunk it was. I'll post a picture or two just for funzies.
 
So here is the action and barrel. I need to turn the OD of the barrel down to the major diameter of the barrel hole in the receiver. The two cartridges show the approximate location of where they would sit in the chamber. So I will have to cut off the breech end at about where the breech end begins to taper into the barrel proper. If you look carefully you will see a hole drilled through the barrel in order to DEWAT it.

For now I need to determine the major diameter of the receiver threads to see if there will be enough meat on the barrel fully fit the full length of the receiver. I will need to have a face that rests against the front of the receiver to act as a depth and headspace stop.

The bullets are the same diameter as are the neck diameter on the 303 and the case diameter on the 32 S&W Long (or 32 Colt New Police, if you prefer). I hope I can get it to work.



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