Fixing a shitty thread job

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[ARCHIVED THREAD] - Fixing a shitty thread job

Posted: 3/12/2017 11:48:06 PM EDT

Friend had a barrel SBR'd.

Short story....threading sucked enough that I think there will be an endcap or baffle strike on the suppressor.

Barrel is about as short as it can go.

Is it possible to go just a 'scootch' farther (maybe an 1/8-1/4") with some of the original threading so there is a new shoulder and better threads to mount the suppressor flash hider?

Or can we weld/solder new material and have it threaded again?

What are the options?

Posted: 3/12/2017 11:58:23 PM EDT

[#1]

When I find myself in these situations where you're really trying to be extremely crafty to save something with a real heroic effort, I pat myself on the back and think "yup, if this was the last barrel (or whatever) on earth, I bet I could save it".

Then I admit it's not, that my time has a lot of value, and I get a replacement.

But that's just me.

Replace it and you'll be shooting in no time with a much greater degree of confidence IMO.

- Chris

Posted: 3/13/2017 12:39:19 AM EDT

[#2]

You know what they say.
A picture is worth a thousand words.

Posted: 3/13/2017 5:56:58 AM EDT

[#3]

Edited. AeroE New bbl.

Posted: 3/13/2017 9:30:56 AM EDT

[#4]

Yup, don't waste your time trying to polish a turd.
Barrel is cheaper than a suppressor

Posted: 3/13/2017 12:53:18 PM EDT

[#5]

A new barrel, definitely. I'd, first, go back to the smith that did the work and get it out of him.

Posted: 3/13/2017 8:34:51 PM EDT

[#6]

Quote History

Quoted:
When I find myself in these situations where you're really trying to be extremely crafty to save something with a real heroic effort, I pat myself on the back and think "yup, if this was the last barrel (or whatever) on earth, I bet I could save it".

Then I admit it's not, that my time has a lot of value, and I get a replacement.

But that's just me.

Replace it and you'll be shooting in no time with a much greater degree of confidence IMO.

- Chris

View Quote

Well, the cost of replacement should be on the machinist.

Posted: 3/14/2017 11:07:09 AM EDT

[#7]

Yeah, it should. But if he hacked it that bad the first time, why trust him a second?

Why was a new short bbl not put on in the first place? Cutting and threading is not the ideal choice.

Posted: 3/14/2017 11:21:36 AM EDT

[#8]

I'd ask class 3 machining.

He's a forum sponsor and he is the BEST.

Not shilling for him, just a satisfied customer.

He'll at least tell you if he can do it or not.

Posted: 3/14/2017 12:36:09 PM EDT

[#9]

It "can be" fixed; the question is, is it worth it?

There are several ways to do it, each will cost more to do than the initial threading itself. The smith should be paying for it.

What firearm? What barrel length?

Posted: 3/14/2017 11:38:26 PM EDT

[#10]

Quote History

Quoted:

Well, the cost of replacement should be on the machinist.

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:
When I find myself in these situations where you're really trying to be extremely crafty to save something with a real heroic effort, I pat myself on the back and think "yup, if this was the last barrel (or whatever) on earth, I bet I could save it".

Then I admit it's not, that my time has a lot of value, and I get a replacement.

But that's just me.

Replace it and you'll be shooting in no time with a much greater degree of confidence IMO.

- Chris

Well, the cost of replacement should be on the machinist.

Can't argue with that on principle but I've gotten to when people have already proven themselves to be bone headed that I feel it's time to figure out alternatives.

Mistakes are one thing that people can correct but I see too much supposed "professional gunsmithing" that seem like total hack jobs that tell me "Run away!". I've got a couple of mills and lathes and I make mistakes too but they are my mistakes on my stuff and I try to learn from them. That's the price I pay for that education.

Paying someone else to booger my stuff and then try to pass it off as OK is just a time waster IMO.

Definitely try to get him to make it right but be ready to walk if things break bad. It's your gear, your money, and your time; be judicious in anyone wasting any of it.

Hope you find an acceptable solution no matter which way you go...

Posted: 3/16/2017 5:54:26 PM EDT

[#11]

Quote History

Quoted:

What firearm? What barrel length?

View Quote

CZ 805. SBR.....can't go any shorter

Posted: 3/17/2017 12:54:49 PM EDT

[#12]

Picture of threads?

Posted: 3/18/2017 12:55:04 AM EDT

[#13]

Replace the barrel for the fastest solution.

If the barrel has some kind of personal value to it, or is otherwise unique (older 1:12 twist for an XM clone), you can always have piece of barrel steel threaded inside and soldered on, then recut to 5/8"-24 and then just use a 30cal muzzle device or threaded can. This kind of oddball fix would be nearly the cost of a new normal barrel, but to preserve a specific, more costly barrel twist, or a "treasured" gun, it would be a fine solution.

Either way, the person who screwed up one of the easiest jobs of a machinist needs to have it fixed.

Posted: 3/18/2017 12:38:39 PM EDT

[#14]

Short version,

Cross slide is set to 29.5º, Tool cutter is set to 90* to the work piece.

As you are cutting threads, you are advancing the cross slide each pass inward , your working from the right hand side of the valley end point, and advancing the cross slide with cutter down the right hand thread wall towards what will be the center of the thread valley in the end, to create the threads. This has the cutter only cutting at the tip and the left hand side of the cutter.

Best guess, who every threaded the barrel, set both the cutter and cross slide to 90* towards the barrel, and was trying to cut both sides of the valley walls at the same time, and it creates a mess since you are working both sides of the cutter.

As for cleaning up the threads by re-cutting the threads, bad idea since it will end up with the threads undersized, and the can threads loose to the under sized barrel threads isntead.

Posted: 3/18/2017 2:26:45 PM EDT

[#15]

Quote History

Quoted:
Short version,

Cross slide is set to 29.5º, Tool cutter is set to 90* to the work piece.

http://img.photobucket.com/albums/v647/Fighter1/P1010744.jpg

As you are cutting threads, you are advancing the cross slide each pass inward , your working from the right hand side of the valley end point, and advancing the cross slide with cutter down the right hand thread wall towards what will be the center of the thread valley in the end, to create the threads. This has the cutter only cutting at the tip and the left hand side of the cutter.

Best guess, who every threaded the barrel, set both the cutter and cross slide to 90* towards the barrel, and was trying to cut both sides of the valley walls at the same time, and it creates a mess since you are working both sides of the cutter.

As for cleaning up the threads by re-cutting the threads, bad idea since it will end up with the threads undersized, and the can threads loose to the under sized barrel threads isntead.

View Quote

BINGO!

Posted: 5/10/2017 8:14:15 AM EDT

[#16]

If you are still working on this, I had a similar sit awhile back. What we did was turn the bbl way down, thread it, and then made a threaded insert or sleeve that sits on top of it. That insert is then threaded to the correct dia needed. Once we refinished, you couldn't really see it, only a slight line if you looked at it head-on at the crown.

Posted: 5/19/2017 9:24:09 PM EDT

[#17]

Feeling generous today, if you are still working on this pm me

Posted: 5/19/2017 9:53:11 PM EDT

[#18]

probably feel better with a new barrel

[ARCHIVED THREAD] - Fixing a shitty thread job

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