Help Me Identify Mystery Threading!

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I've wasted lots of money guessing, all I learned is that .578x28 and 9/16x24 do not fit (barrel thread OD is too wide). 5" Glock 20 10mm auto barrel





 
A set of thread pitch gauges would be really helpful.. Maybe turn your calipers around, switch them over the metric and measure from the bottom of one thread to the next. If it is from a Glock there is a good chance it will be metric.
 
It's 5/8 but the thread count is super fine, like 5/8-36, I've never heard of that thread but does not mean it doesn't exist
 
I went to a bolt supply place and apparently we are looking at 5/8x40. So my next question is wtf sort of attachments use that pitch?
 
Why don't you contact GLOCK???? There are a few possibilities such as a GLOCK proprietary thread and pitch for a Glock muzzle brake or silencer. Silencers are legal and encouraged in some European nations. That could easily be one of those barrels. Did you get a pistol with it or is it a replacement barrel?
 
Probably cheaper and easier to have it turned down to a standard size rather than try and find a muzzle widget to fit it
 
If you have it turned down chances are there won't be enough meat left for a different thread.

You NEED to buy a pitch guage or at least offer up other threads to the stub to see if the threads on various pitch screws engage. They don't need to be the same diameter. You're just looking to use the other screws as a pitch guage. Try a variety of imperial number sizes and metric pitch screws to find one that has thread peaks that nestle in the thread valleys of your barrel for the whole length of the threaded stub. From there you can find the proper size.

Note that the major diameter of the thread which you give as .623 is not really going to tell you the actual thread size. Granted the .623 is preciously close to .625 which is 5/8". But threads are seldom so close thanks to the dressing off on the peaks of the threads. If I had to guess at a screw diameter from the .623 I'd likely try some metric screws or thread gauge sizes based on it being a 16mm size stub which is nominally 0.630". The .007 difference between the nominal 16mm to the measured .623 would be far more typical.

Regardless you won't be able to find that size tap or die at the local lumber yard or local Princess Auto. There's a world of special thread sizes out there in "engineering land" that are supported. But only by buying from such places as KBC Tools or Enco or other special tooling outlets.

And in fact when I go to the Enco website and look up "metric special" sizes there is a 16x0.75 mm size tap. So see if you can find a 0.75 mm pitch screw and see if it matches up. I would be surprised if there are not also 1mm size pitch taps as well. But when I try to find a table of sizes at KBC their website is not able to do that and clicking through the list of taps with no description is way too time consuming.
 
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BCRider said:
If you have it turned down chances are there won't be enough meat left for a different thread.

You NEED to buy a pitch guage or at least offer up other threads to the stub to see if the threads on various pitch screws engage. They don't need to be the same diameter. You're just looking to use the other screws as a pitch guage. Try a variety of imperial number sizes and metric pitch screws to find one that has thread peaks that nestle in the thread valleys of your barrel for the whole length of the threaded stub. From there you can find the proper size.

Note that the major diameter of the thread which you give as .623 is not really going to tell you the actual thread size. Granted the .623 is preciously close to .625 which is 5/8". But threads are seldom so close thanks to the dressing off on the peaks of the threads. If I had to guess at a screw diameter from the .623 I'd likely try some metric screws or thread gauge sizes based on it being a 16mm size stub which is nominally 0.630". The .007 difference between the nominal 16mm to the measured .623 would be far more typical.

Regardless you won't be able to find that size tap or die at the local lumber yard or local Princess Auto. There's a world of special thread sizes out there in "engineering land" that are supported. But only by buying from such places as KBC Tools or Enco or other special tooling outlets.

And in fact when I go to the Enco website and look up "metric special" sizes there is a 16x0.75 mm size tap. So see if you can find a 0.75 mm pitch screw and see if it matches up.
Click to expand...

Read post #5. :)

He will have enough meat if he threads it 9/16-24. It's a standard thread size for 10mm barrels. Add to that he will actually be able to buy a muzzle widget in that size, again, because it's common.
 
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I actually already have a 9/16x24 protector. It's the first one I tried but was obviously wrong when I was able to look at the barrel in person.
 
Where did you get the barrel?

StormLake doesn't seem to offer 10mm barrels threaded on their site (Although I could have missed it), let alone in that size.

My guess is that someone added their own unique thread pitch, possibly by accident.
 
I got the barrel off the EE for a great price. Storm lake no longer makes this model. After talking to a few of the employees it really seems that this was not done by them.
 
Take it to a machine shop. In a minute or two they'll tell you what it is. I'd be happy to do it for you if you weren't so far away, but that would require postage 2 ways.

Could be 5/8 x (pitch?) or 16mm x (pitch?).
A metric and a standard thread gauge would quickly determine which.
 
*MALICE* said:
Read post #5. :)

He will have enough meat if he threads it 9/16-24. It's a standard thread size for 10mm barrels. Add to that he will actually be able to buy a muzzle widget in that size, again, because it's common.
Click to expand...

I would not have thought that it would work. But if that's the common size for 10mm barrels then fine.

What will happen is that he, or more correctly, the machinist doing the job will not be able to remove all of the existing threading without making the new threads too short. So the tops of some of the new threading will still have a rough look from the valleys of the old thread where they overlap. Lining up the engagement of the cut might or might not limit this by keeping the peaks of the new thread in the meat from the old. But at some point the threads will coincide and the new thread will have a dog chewed look on some of the job. It'll be slight for sure since the existing threads are pretty fine so they aren't all that deep. But it'll still have some mixing of the old with the new.
 
BCRider said:
I would not have thought that it would work. But if that's the common size for 10mm barrels then fine.

What will happen is that he, or more correctly, the machinist doing the job will not be able to remove all of the existing threading without making the new threads too short. So the tops of some of the new threading will still have a rough look from the valleys of the old thread where they overlap. Lining up the engagement of the cut might or might not limit this by keeping the peaks of the new thread in the meat from the old. But at some point the threads will coincide and the new thread will have a dog chewed look on some of the job. It'll be slight for sure since the existing threads are pretty fine so they aren't all that deep. But it'll still have some mixing of the old with the new.
Click to expand...

......I think you're mistaken :) . How deep per side do you calculate the threads of a 40 pitch thread to be?

Even if you were to calculate them at .03" per side (which is deeper than they actually will be) you would be at .565".

9/16" is .5625" and you are gonna be turning the od to a few thou smaller than that before threading.

The OP will be good to go
 
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