can you cut .578x28 threds into a muzzle accessory that was 1/2x28?

It seems like if you cut away all the old threads the hole might be too big. Can a guy just cut into the threads at the 28 pitch a little deeper to turn .500" into .578? Looking to adapt an AR muzzle accessory for pistol use.

Thx

The part can be rethreaded to a larger size. Not by running a tap in, unless you want a wreck to fix.

Look at the difference in diameter, it's 0.078 inches. I'll guess the muzzle device is 9/16th's inch nominal. A quick look around the 'net will turn up thread size tables. Pay attention to the thread pitch, too.

Dirty math says tap drill for .578-28 is .5423, so with a drill and tap it should clea
To find tap drill diameters- (major diameter)- 1/(pitch)

what the hell is .578?





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Probably a rough measurement of a 9/16th's thread.

It must be, but it makes me question the 28 pitch...
9/16 NEF is 24, with 27 being closer standard.

At any rate, you can go to anything 9/16-18 or finer from 1/2" and be OK.

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I didn't bother to dig out a thread table today, so I didn't know if 28 pitch was normal or not.

Might be a good idea to measure the brake or silencer and the threaded barrel to for sure.

.578x28 is like the standard imperial right handed thread for 45 cal pistols, at least in the US. That is the size of most 45 cal muzzles and suppressors.

will there be enough meat in a used to be 1/2x28 flash hider to cut the .578 threads after you drill out hte .500 threads? Or can you just run the .578 tap right into the .500 threads an cut deepen the threads that are already there?

I'm more interested in your source for a tap now.

If a 0.578 X 28 thread is standard for muzzle devices, it's a special thread.

I also see that other folks have been in the same boat before you. Check in the silencer forum to see if anyone has a source for a tap. I think you'll have to hire someone with a lathe to cut the threads for you. I never did find a place that would make a custom tap.

You can look at a tap drill chart to figure out the undersize dimension you'll need to open the bore before tapping. Or drill it 1/64th of an inch under; I'm not so sure I would do that with a muzzle device.

It's true, too. Better plan to say Bad Words, too.

Was planning on having a machinist do the werk on a lathe. Jus wasn't sure if the 1x28patient was something he could start with.

The threads can easily be cut in a lathe by the right operator. A little boring bore is used to get inside the part. Be sure you use someone that understands the need for alignment of the bores.

0.578" is the standard 45 can thread.

It is 37/64".

CP

Do you have a tap or a die?

What you're saying was already established, although I would like to know which numb nuts selected a nonstandard thread. If I get some time I'll look to see if the obsolete American National Standard threads included one of this size. Anything is possible due to the age of the 1911 and the Wild West of thread standards in the first half of the 20th Century. I don't see a Whitworth thread that matches.

Just from eyeballing mine, it looks like someone dipped their sack in novacain, chucked up a 1911 barrel, and turned 28 pitch threads until they were pointy, then measured it. The major diameter of the thread is, by eye, the same as the OD of the barrel.

And I really want whoever came up with this plan to step away from the lathe and never work on another gun again. I have no desire to single point oddball internal threads.

Im not sure what to make of your drivel.

What's the barrel OD? If its .581, that sounds about right.

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The big diameter of the wrinkly part is about the same as the big diameter of the smooth part.

outstanding explanation sir

It takes some effort, but I can talk all technical like that occasionally

.578-28 tap/die set

spendy though. found an expired auction for the tap alone around $65

You should probably find out what the nominal drill size is and drill out the original threads. There will likely be enough thread left to start the tap into and keep you lined up at least. Contact the vendor above, hopefully they'll have the info you need. Also, make sure the FH you are cutting is not hardened like the Vortex or you'd be better off burning your money than trying to re-tap it.

Probably a suppressor for a .45 Auto.

I've single pointed all the ones I've done.

We figured that by about the third post.

My 1-3/16-16 tap came in today. Woot.

Whut're you gonna tap with that, a water main?

Yup, putting in an extension.



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what is "single pointing" The smith said he doesn't have the tap and he doesn't have the gears to cut them w/ the lathe.??

he's gonna try to get a tap.

Someone told him 13.8mm is the size to drill to cut these threads, that is about .543"

Single pointing is done in a lathe with a tool held in a boring bar.

Did you look for a 13.8 mm tap?

If you can't find one here: http://www1.mscdirect.com/eCommerce/NavigationServlet/Threading/Taps/_/N-77h0t?cm_re=Category-_-HomePage-_-Taps, you should plan on a custom tap.

Your gunsmith is about to screw up your suppressor. 0.543 is not similar to 0.578 inches, either.

If I were you, I would get a copy of the Machinist's Handbook and dig into the thread tables in order to understand just exactly what all these dimensions mean, especially with respect to major and minor diameters and fits on male and female threads.

The guy sounds a little out of his depth.

UPDATE:
smith ordered a 37/64th die/tap set, bored out the levang linear comp and tapped it to 37/64th. But I couln't thread it on to either of my .578x28 barrels even a little bit, one by lone wolf, one by KKM.

The Tap only had about a 1/4" of taper on it so it was able to get in deep enough cut to full diameter.

I called silencerco who made my 45 can, and he offered to chase out the comp w/ his "class three custom made .578x28" for free.

I guess you can't just use just any 37x64th tap.


Like the guy above said ...

Did your guy bother to measure the threads, with wires or a gage?

Your "Gunsmith" is an idiot that must like buying suppressors for his customers.........................................

The only acceptable way to thread for a can and be assured of axial alignment and concentricity TO THE BORE is single pointing on a lathe by someone who actually knows what they are doing.

You need to find a new "Goonsmiff"

Guys, I should point out that he was not threading a suppressor, just a AR15 muzzle flash suppressor/comp (levang linear) with an oversized bore, so alignment is not as important. Reason is b/c it goes on a SBR w/ a very short and barrel and stock and I am trying to keep some of the muzzle blast and powder fleck away from me.

Also, for what it is worth, he installed the tap on a lathe to cut the threads. Anyway, than gosh for the nice guy at silencerco.

Got the muzzle device back from silencerco and it works great now. Custom class three bottom tap.

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