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3/17/2011 5:37:14 PM EDT
Can threads (muzzle) on an AR barrel be repaired?
3/17/2011 5:39:13 PM EDT
[#1]
What's wrong with them?

The answer to your question is "yes", but that comes with lots of caveats without more information.

3/17/2011 7:02:08 PM EDT
[#2]
Quoted:
What's wrong with them?

The answer to your question is "yes", but that comes with lots of caveats without more information.




Yup- if it is minor damage you can "Chase" them or clean them up with a thread file.
If they are badly damaged you can turn down the threaded portion to about 3/8ths and make a bushing that you silver solder on, then turn and thread it.

3/19/2011 10:10:51 PM EDT
[#3]
you could buy the die and run it over the threads.
3/21/2011 5:30:40 PM EDT
[#4]
Quoted:
you could buy the die and run it over the threads.


Run a die over them and you will end up with undersized threads.
Better to use a SAE thread repair file or find a lathe.

3/22/2011 2:55:16 AM EDT
[#5]
Quoted:
Quoted:
you could buy the die and run it over the threads.


Run a die over them and you will end up with undersized threads.



How so?

3/22/2011 10:40:00 AM EDT
[#6]
Quoted:
Quoted:
Quoted:
you could buy the die and run it over the threads.


Run a die over them and you will end up with undersized threads.



How so?



Common off the shelf dies are made for typically a class 2A fit, general loose tolerance threads acceptable for general use i.e. bicycles and lawnmowers.
I personally don't feel that is acceptable for a firearm. When I turn and thread I shoot for a tight 2A to 3A thread fitment.
When you run a die down a piece of round, virgin material the cutting edges of the die experience substantial loading which causes a certain amount of "spring" to them. As a result your threads are close to a 2A fit. This is by design.  When the die is removed it relaxes somewhat and the cutting edges spring back. It is only a very small amount, maybe a thou or so but it is there. Now when you run the same die over a part that is already threaded the likely is high that the threads will be a smidge undersize, nearing a 1A fit (sloppy).
You can counter that effect with an adjustable die somewhat but you almost need to measure what the major/minor diameters.
I may be overthinking it a bit but I did have to rework 100 parts in a shop once on my time and material because I tried to cheat a bit and used a die instead of singlepointing the threads like the boss had told me to do, the threads ended up out of spec and I ate the parts.

I guess it is your call-if all you are going to run is a flashhider on the rifle a smidge under probably will cause no issues. But if you are going to be running a brake or a can then you want that threading as precise and close fitting as possible.
FWIW the difference between classes of fit on a 1/2" thread is only .0015 or one and one half thousandths.


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