What thread size and why?

[JohnGalway]

Hi folks,

 

For once I am being an optimist. The light at the end of the tunnel perhaps isn't the oncoming train

 

So, I'm thinking ahead to when my Supernintendo grants me my moderator permit - or whatever it's new incarnation will be. I'll need to get my rifle barrel threaded to accept the new mod.

 

I've pretty much decided I want to get an ASE Jet-Z CQB. My rifle is a Remington 700 VL SS, so it's got a varmint barrel.

 

I know there are different thread sizes, but to be honest I know sweet #### all about them. What're the pro's and con's of the different sizes please?

 

ATB,

 

John

[Ronin]

You probably didnt expect a reply at this time in the morning, however as ive just finished an "evening" shift and winding down with a dohnut and extra large coffee , I will attempt reasonable answer.

 

 

I am guessing that your muzzle diameter is around .800" (maybe a bit more)

 

 

You would have to check with the thread sizes available for the moderator with the importer, but from the ASE site these:

 

Standard threads include; M14x1, M17x1, M18x1, ½"x20 UNF, ½"x28 UNEF

 

Are available.

 

 

I have fitted a few of these mostly in 1/2UNF and M14x1

 

 

Your barrel diameter is roughly .800" (20mm)

 

 

So you barrel would accommodate a thread at the largest size of M18x1mm leaving a strong threaded section of barrel near the muzzle to support the moderator.

 

If however you chose a 1/2 UNF - the gunsmith would have to turn the barrel down (for threading ) from .800 to .500"

 

That frankly would look silly and does...

 

 

Better to get the largest thread size possible IMHO

 

 

Threads

 

M18x1mm (18 mm diameter, 1 thread per mm)

 

1/2 UNF (20TPI) - .500" Diameter x 20 threads per inch.

 

1/2 UNEF (28TPI) .500" diameter x 28 threads per inch.

 

 

And so on and so on.

 

 

Some ASE moderators require shoulders machining on the barrel thread tenon by the way.

 

Your smith needs to either have the moderator when he machines the barrel or know what type of thread / shoulder size he is making.

 

 

Hope thats easy t follow..

[JohnGalway]

That's absolutely perfect Ronin, thanks very much M18x1 sounds the best to me as it leaves as much of the barrel there as possible for a bit of strength as you rightly say

[1967spud]

mine are both done 18x1 for jet-z's and as ronin say you get a really beefy thread for support

[17 Rem]

If you prefer the looks of a larger thread, then fair enough.

However, it always puzzles me to hear people claim a strength advantage to larger threads. Has anyone ever seen a muzzle fail in some way purely because it was threaded 1/2" UNF?

1/2" UNF suits me just fine.

[1967spud]

i spose its the more metal there is together the more surface there is to give a better contact point, i agree that moddys dont fly of but it does help them with support

[Ronin]

Its common sense to use the largest diameter thread to the barrel diameter.

 

Yep I mentioned strength, this may or may not be a "real or percieved" factor on my part - I am NOT a metalurgist or engineer so unable to quantify my feeling.

 

 

I also do not like making 1/2UNF threads on .30 cal rifles.

 

 

If you work out the math, you will understand why:

 

.30 cal = .308" bore

 

Thread 1/2" = .500" tenon.

 

Therfore you have a barrel wall of .099" over the entire length of the tenon (usually .650" in my case)

 

Factor in thread depth - .065" (or thereabouts)

 

 

 

And you have minimal structural strength on that section of the barrel - but, as I said, I am not an engineer.....

[Ronin]

Sorry, moved this "thread" to the tech section as it fits the criteria.

[JC275]

A Riflesmith that I spoke to recently said that there was a school of thought to standardise threading at M14x1 for sporter type barrells and M18x1 for heavey barrells wherever possible. Sounds like a good idea to me except that a lot of engineers only have the tooling to do Imperial threads. JC

[Ronin]

A Riflesmith that I spoke to recently said that there was a school of thought to standardise threading at M14x1 for sporter type barrells and M18x1 for heavey barrells wherever possible. Sounds like a good idea to me except that a lot of engineers only have the tooling to do Imperial threads. JC

 

 

If only the industry used standard thread sizes with the threads they make!

 

 

One M14x1mm from one manufacturer is not the same as another M14x1mm from another. This is true in many different sizes.

 

 

It helps to have the moderator nearby to test fit, some threads conform more than others to "industry standard"

[JohnGalway]

Standardised threading is something that'll happen sooner or later IMO, it's like standardising charger sizes for mobile phones, a good idea.

[ejg223]

Ronin I thought there is only one M14x1 and that is the iso standard.

One can make it larger or smaller but then it aint m14x1 and can be rejected.

If the small tolerance that a M14x1 has when produced within iso standard is too much for the mod

mounting, then the whole design is flawed and a mod should be fitted by other means.

A mod bought in UK for example must be able to fit on a factory threaded rifle from anywhere

in the world. That is why we have ISO standards. One should not need a fitting process by a smith.

A rifle must be threaded to standard by a smith to ensure that any mod off the shelf with that thread

in the future will fit that rifle. If a mod has a out of tolerance thread, then it should be sent back

to the supplier and rejected, not a rifle threaded to suit an out of tolerance thread.

 

I like to have a bit of a shoulder left for the mod to sit on and at the same

time not too thin wall section.

M15x1 isn't a bad size either for anything a bit bigger than a sporter barrel.

Agree, 1/2" and 30 cal is no good.

 

 

John, just have a chat to Fergal Whyte in Athlone, he did a great threading job on a friends rifle and

has a few moderators in the shop. Very good prices too.

James Clark has a new moderator out that might be better value and good quality. Think Ronin

is testing one.

 

edi

[JohnGalway]

I've heard Fergal Whytes name mentioned before, shot I was at is just outside Athlone and I got quoted €400 for the mod plus €50 for the threading itself.

[Ronin]

Edi

 

 

just to expand what I posted.

 

 

Any thread be that M17, M14 5/8th UNF, 1/2 UNF etc etc etc

 

 

Has a set diameter 17mm, 14mm, .625" and .500" in the examples above.

 

 

That is set in stone.

 

 

What I mean is that when you cut the threads and apply thread guages until they fit and run smoothly for say a class B fit.

 

Then run on the mod (be that from x, y or z manufactuer)

 

 

Some do not fit as well as others and may require and extra .001" cut or more of thread depth.

 

 

Tiny differences,

 

Sorry if I was unclear, but not all mods "fit" the same as others.

[ejg223]

Ronin,

 

If you order a spare piston for youre discovery.. what do you do..

measure it , put it on the lathe and take a bit off? no you don't

you expect it to fit

The tolerance system was developed to put a stop to all this.

 

But I understand where rifle smithing comes from, cheap mass produced

rifles built with "large" tolerances get .. lets say fixed.

edi

[eldon]

Going back a bit in the thread.....

 

One line of thought goes like this;

If you were to remove a large amount of material, say 20mm barrel down to 12.7mm (1/2" unf) not only would the area be weaker (although apparently acceptable to some) but the following could occur. Then and especially if the barrel in question was hammer forged, you could stress relieve that section and allow it to grow in terms of bore size. Now as most people know, and think of a shotgun and its chokes if it makes it easier, the last thing you want on a barrel is a bigger dimension at the muzzle. Now you have relieved this area the bore dimension is permanently altered for the worse.

 

Although the thread at 1/2" is not "weak" as such, with a 30 cal hole in the middle it does not leave a lot of material between the root of the thread (which is not 1/2") and the size of the bore.

 

Biggest thread is best advice.

 

p.s. I have a similar rifle set up and my T8 is screwed onto a 5/8ths thread. Nearest up size to this if they don't do this size, is 17 x 1mm of the already mentioned options.

[Ronin]

These are all take off or barrels that ive chopped for alteration, however, the waste ends with threads have been kept as they come in useful for making pillars and the like.

 

Left to right (all about .850" muzzle diameter)

 

5/8th UNF, M18x1mm, 1/2" UNF

 

 

1/2" UNF on a large diameter barrel is just "wrong"

 

 

 

Two examples of "standard" 1/2"UNF barrels that came to me for rethreading due to "issues" - these are NOT my threading!!!

 

All are not equal

 

[MJR]

The 1/2" thread on the lower left looks like it was cut with a hand die not screw cut.

Ronin, do you ever spigot barrels so the mod is aligned on that rather than the thread and barrel shoulder?

[Vermincinerator]

Edi, what Andy is saying is that the moderator makers are not making there mods to standard fits.

I found exactly the same as him, if i cut a muzzle thread to a class 2A fit using a ring gauge, some mods wont go on at all some are good but most flop around like a limp ####!

If the mod makers used a class 2A plug gauge then all would fit perfectly.

In general engineering customers will specify a fit class for threads and if this class is not adhered to not only will the mating part fit poorly but the job will be scrap.

 

Ian.

[ejg223]

Ian, that'll get better when mod manufacturer have to recall all their produced moderators and have to compensate.

Why don't they start making wheel nuts? They'll find out then how to cut threads.

Sorry, I can't accept cutting a that which promotes growth and vigour thread on a rifle to fit a that which promotes growth and vigour mod thread. Change

mod and you are in the....again.

In the car industry there is now no more reject rate accepted. none, not even 1 in a million.

 

Some of my last mods I got without threads and cut them myself. The fine threads

seem to be a much nicer job.

 

Ronin, nice example. I've had enough already when the shoulder is rough as hell on a thread job.

 

edi

[Ronin]

The 1/2" thread on the lower left looks like it was cut with a hand die not screw cut.

Ronin, do you ever spigot barrels so the mod is aligned on that rather than the thread and barrel shoulder?

 

 

It possibly was, its as bad as they come....fortunately not my doing..

 

 

 

Yes I do spigoted shoulders, when the mod requires it (not all do)

[JohnGalway]

Got permission from the law last night to go an buy a mod for my .223, finally

 

Any last thoughts on mod types. Weight and price have become issues, but I may yet plump for the ASE, got some ringing around to do Monday!

[Foxshooter]

Looks like someone couldnt even be bothered to undercut the thread on the left hand example. Was the mod clipping by any chance? I'll bet the mod wasnt sitting square.

 

My heavy barrelled rem700s are threaded 5/8" UNF while my skinny barrelled .308 is (I think) 9/16 UNF

 

My opinion is that 1/2" UNF is a rimfire and airgun thread but then again most of my rifles have fat barrels. I have a nice new Shilen super select match barrel for my stalking rifle to fit soon. I'll probably end up with the same thread pitch again rather than buy another moderator.

 

Mark

[weejohn]

Got permission from the law last night to go an buy a mod for my .223, finally

 

Any last thoughts on mod types. Weight and price have become issues, but I may yet plump for the ASE, got some ringing around to do Monday!

 

fantastic news john, about time too.