1/2 in UNF barrel thread

[Woodlander]

I’ve just bought a used rifle, unseen,(first mistake) which should have a 1/2 in UNF muzzle thread. My ASE SL5 mod screws on just shy of 3 threads, then jams.  Diameter is .501/2 and has 20 tpi, so seems correct. I’ve used the ASE on a previous rifle and screwed on fine, so I suspect the barrel thread.  

Id have to send the rifle away as there are no gunsmiths locally, should I attempt, or get someone more adept, to carefully re cut the thread?  There are many good engineers on the island, but they’re not gunsmiths, by any means.  

 

[Kalahari]

Find a specialist in fastenings and try a series of nuts very gently. It could be 1/2" unef. Still if a genuine 1/2 unf nut screws on easily the problem is elsewhere. This will be a great deal cheaper than getting the barrel re-cut. Also there are problems with leaving a rifle with someone who is not an RFD.

David.

[Woodlander]

Yes, first step would be to take the thread protector along to get it identified. Being 1/2 in diameter and 20 tpi, it has to be UNF, maybe just badly cut?! Would running a 1/2 in UNF die over the thread tidy it up? Wondering if this is a possibility? Of course I wouldn’t leave it with anyone, I’d have to be there.  

[Bangbangman]

I had this problem with a new rifle. I carefully ran a die over the threads, which removed a tiny amount of metal, and my 1/2UNF Ase Utra fitted fine thereafter. 

I'm certainly no engineer/gunsmith (the tap and die set were from Aldi, bought on a whim years ago!) so I suspect someone more experienced would have no problem. 

If things went wrong, you're looking at shorten and recutting anyway. 

[onehole]

You could also check your Ase for having clean threads,,,it may have suffered some burnt powder residue being blown back in its previous application and now causing a stoppage. A stiff close fitting bristle brush may do the job or if particularly hardened crud is in there maybe gently running a tap through will remove it.?..O

[gunner223]

Woodlander,  if its going a fair way down the thread already i would use a small wire brush often found in welding shops,

Wire brush the threads ,then place copper slip on the thread, or a good  grease, and keep twisting it down, it will finely get to the end,

Also can you try another mod with the same thread, it could be your mod that's at fault and not the new barrel.

ATB

[Woodlander]

The barrel thread seems on the large side.  I took the thread protector along to an engineering company, The thread was apparently very loose fitting on a 1/2 in UNF thread, yet it screws on very tightly to the barrel thread.  I think I’ll carefully run a die over it and see what happens. If I’m gentle, it should follow the thread and remove a small amount of material, that’s the idea, anyway.  

[terryh]

Woodlander,

running a die nut or even better an adjustable die down the thread is a simple task - if you take it easy!!

found this bunch useful in the past:  https://www.tracytools.com/

Terry

 

[dully1963]

As said before it's probably a 1/2" UNEF thread a picture of the thread might help people

 

 

[Woodlander]

15 minutes ago, dully1963 said:

As said before it's probably a 1/2" UNEF thread a picture of the thread might help people

 

 

UNEF has 28 threads per inch, mine definitely has 20, which I’m sure means it’s a badly cut UNF.  I took the thread protector to be checked and they confirmed it was a loose UNF, yet very tight on my barrel. 

[Woodlander]

Managed to obtain a die nut locally, a lot more swarf came off than I had imagined.  Now my mod threads on nicely and tightens up well.  Thanks for all the advice. Now just have to remove a broken off rail screw.  Unfortunately it’s sheared off below the level of the action, so not an easy fix. It’s the rearmost one, on a Remmy, so I believe the thread is straight through.  Any advice regarding extraction, would be most welcome.  

[ColinBR]

Drill a small hole in the centre of the screw and use an 'easy out' to turn the screw out. 

[Dellboy]

use a left handed drill to drill the hole they sometimes uncrew the thing while drilling

[terryh]

Apply a bit of heat locally first, in case some *uck-whit has used the wrong grade of thread locking fluid!!

this will break down the bond (a bit)

T

[Woodlander]

I visited one of the local engineers, they’re a bit rough and ready, but he had a couple of aerosol cans, one freezes the metal, shrinking the bolt, the other contains an oil that penetrates the thread.  He then advised using a left hand drill, which may grip and turn it out. He didn’t have an ‘easy out’, but I’ll see if I can buy one, if the drill thing doesn’t work.  

Thanks again and fingers crossed, I may get to shoot this before Christmas.....

 

[Mattnall]

On 8/27/2019 at 8:29 PM, Woodlander said:

Diameter is .501/2 and has 20 tpi, so seems correct

1/2" thread is usually cut on a slightly smaller diameter, this seems a bit large. According to my book of words the major diameters should be max 0.4987- min 0.4906 for a class 2A and max 0.5000 - min 04919 for 3A.

That couple of thou oversize seemed to be the problem