Order of operations, Barrel Threading.

[spitfire_er]

Was pondering this morning. Most guys, including me, will in general indicate, thread, (indicate again) chamber.

Say you indicate the throat area, and get it dead true before chambering. Wouldn't there theoretically potentially be a chance that the rear of the case not being concentric to the threads, therefore not concentric to the bolt action etc... says it perfectly concentric, but has a 0.0002" wobble from say a floating reamer. Then the centerline of the case is not imposing forces 180 degrees straight back centerline of the action? I'm not talking thousandths, but a few ten thousandths of an inch or less.

Granted if everything is perfect, you can achieve a zero runout, or dang close to zero if everything is indicated properly and held tight.

Wouldn't there be a better chance to align threads to the case when indicating off the neck/ throat, and the rear of the chamber? This intern MAY allow for a more accurate thread chamber job in relation to the reciever/bolt. If nothing else possibly minimizes the potential for any runout?

Thinking as to why most people indicate, thread, then chamber I believe goes back to the days when almost everyone chambered in a steady rest. A common practice was to thread, then move the steady to the threads, then chamber to try and get everything running true. This method still works great for many folks, but I think that's why it's more common to do that order of operations vs chamber then thread.

I know some people will say my standard barrel procedure produces total zero runout and I don't argue that, but just general chambering procedures. Am I nit-picking, or has anyone any real measurement proof of one vs the other being more concentric over several jobs?

I'm always open to learn something new and appreciate all the good and knowledgable folks here.

 

[butchlambert]

Threads do not center the barrel. If your shoulder is perpendicular to your chamber, you are good to go. That is what squares it up if you are talking tenths.

 

[Dusty Stevens]

Who changes their setup in the middle of the job?

 

[Alex Wheeler]

If the barrel is moving, re think your setup.

 

[spitfire_er]

Threads do not center the barrel. If your shoulder is perpendicular to your chamber, you are good to go. That is what squares it up if you are talking tenths.

Makes sense. But what about square threads? They aren't going to do much centering unless they are snug.

Who changes their setup in the middle of the job?

Several well known people here I've read indicate, bore, then re-indicate, then chamber. That to me is changing a setup in the middle of the job. Didn't say I did. When I said "(indicate again)", I usually don't do that unless needed to make sure neck/ throat area is true. That being said, I believe I did read an article one time naming a well known BR shooter and Smith that said he once dialed in a barrel, came back the next day to thread/ chamber and it was no longer running true.

If the barrel is moving, re think your setup.

Mine doesn't move.

 

[Dusty Stevens]

I believe I did read an article one time naming a well known BR shooter and Smith that said he once dialed in a barrel, came back the next day to thread/ chamber and it was no longer running true.

once a machine warms up and establishes its oil wedge I can see it changing overnite. anytime I plan on doing any indicating I turn my machine on and let it spin and warm up while I'm getting things ready. you wouldn't believe how long it takes oil to get up to temp and then get your spindle up to temp. I learned this from making tools on a surface grinder where it may take a bunch of setups over a few hours time.
I'm an advocate of warming up a machine and doing a barrel in one setup. I do not have time to do a barrel over a few days time. if you cant do a barrel in one setup from start to finish I recommend you not do it until you can dedicate the time to finish it. chambering a barrel is not a week long project nor is it a go take a nap an d finish it later thing either. of course im sure some great barrels have been done as a project- anything is possible- but not for me. if I cant finish it i'll do some smaller things with that time. I do know how setups change over time and wont let that happen to my setups.

 

[spitfire_er]

anytime I plan on doing any indicating I turn my machine on and let it spin and warm up while I'm getting things ready.

I'll admit this is something I have never thought of before and will do from now on. I do my barrels on the same day. Maybe a muzzle on a different day, but once I get going, I like to see it through.

 

[butchlambert]

Makes sense. But what about square threads? They aren't going to do much centering unless they are snug.


Several well known people here I've read indicate, bore, then re-indicate, then chamber. That to me is changing a setup in the middle of the job. Didn't say I did. When I said "(indicate again)", I usually don't do that unless needed to make sure neck/ throat area is true. That being said, I believe I did read an article one time naming a well known BR shooter and Smith that said he once dialed in a barrel, came back the next day to thread/ chamber and it was no longer running true.


Mine doesn't move.

Sir, if you have done sq threads, like on my mod17 Enfield, they still do not center on the threads. It is squared up with the shoulder. Oh, my rolling block is the same.
I do thread first, but I do check the throat before chambering.

 

[spitfire_er]

Sir, if you have done sq threads, like on my mod17 Enfield, they still do not center on the threads. It is squared up with the shoulder. Oh, my rolling block is the same.
I do thread first, but I do check the throat before chambering.

I've done several dozen square threaded barrels particularly M1917's. While I don't build them like your one custom rifle, IMO, mine are nicer than 99% of them out there and they all shoot. I'll have to respectfully disagree with that statement. While the shoulder may help square the barrel, it will do nothing to center it with square threads. That's the threads job to center it, and on a square thread, they must be a tad more snug than you can get away with on standard 60 degree threads. Square threads don't self center. Tell me how two 90 degree surfaces impose anything other than 180 degree opposing forces to each other.

To go a step further if you have short threads and deep grooves on a square thread, you can easily tighten a barrel snug on the shoulder and have it not centered or concentric to the reciever.

I do know however that a correct 60 degree thread will by geometry, tighten up and self center itself. That makes perfect sense to me.

 

[butchlambert]

I've done several dozen square threaded barrels particularly M1917's. While I don't build them like your one custom rifle, IMO, mine are nicer than 99% of them out there and they all shoot. I'll have to respectfully disagree with that statement. While the shoulder may help square the barrel, it will do nothing to center it with square threads. That's the threads job to center it, and on a square thread, they must be a tad more snug than you can get away with on standard 60 degree threads. Square threads don't self center. Tell me how two 90 degree surfaces impose anything other than 180 degree opposing forces to each other.

To go a step further if you have short threads and deep grooves on a square thread, you can easily tighten a barrel snug on the shoulder and have it not centered or concentric to the reciever.

I do know however that a correct 60 degree thread will by geometry, tighten up and self center itself. That makes perfect sense to me.

That's OK, just do what you feel comfortable with.

 

[spitfire_er]

Am I missing something? I always open to learning or correcting something I can improve on. Unless explained otherwise, it doesn't add up with all of the geometry and physics courses I have taken in high school and more so in college. More importantly, the experience myself of actually installing these types of barrels.

I know you've done a lot of barrels Butch. That's why I usually agree with 98% of what you have to offer.

 

[butchlambert]

You have a PM, no use taking up space on the forum.

 

[msinc]

.....While the shoulder may help square the barrel, it will do nothing to center it with square threads. That's the threads job to center it, and on a square thread, they must be a tad more snug than you can get away with on standard 60 degree threads. Square threads don't self center. Tell me how two 90 degree surfaces impose anything other than 180 degree opposing forces to each other.

To go a step further if you have short threads and deep grooves on a square thread, you can easily tighten a barrel snug on the shoulder and have it not centered or concentric to the receiver.

I do know however that a correct 60 degree thread will by geometry, tighten up and self center itself. That makes perfect sense to me.

I agree the square threads are not self centering {unless of course they are very close tolerance to one another and have no play to off set}. The shoulder definitely squares things up between the barrel and the receiver. Many people question this when I tell them and they believe it is the threads themselves that square things up.
The only rifle I have barreled that used a square thread is the 1903 and 1903A3 Springfield. It's been a while, but if I remember right they have a recess in the front of the receiver and a "stepped shoulder" {for lack of a better term} on the barrel tenon that centers the barrel to the receiver. Never played with a 1917 and never intend to. In fact, I cannot name another rifle that does use a square thread {Krag maybe??? I doubt it though, I seem to remember they used a square on the 1903 because of the higher pressures of the then new smokeless powder}.

 

[Doug Beach]

Acme and square threads are not the same thing.

 

[butchlambert]

I agree the square threads are not self centering {unless of course they are very close tolerance to one another and have no play to off set}. The shoulder definitely squares things up between the barrel and the receiver. Many people question this when I tell them and they believe it is the threads themselves that square things up.
The only rifle I have barreled that used an Acme thread {what you guys are calling "square" thread} is the 1903 and 1903A3 Springfield. It's been a while, but if I remember right they have a recess in the front of the receiver and a "stepped shoulder" {for lack of a better term} on the barrel tenon that centers the barrel to the receiver. Never played with a 1917 and never intend to. In fact, I cannot name another rifle that does use an Acme thread {Krag maybe??? I doubt it though, I seem to remember they used an Acme on the 1903 because of the higher pressures of the then new smokeless powder}.

Google is your friend. An acme thread is different than a square thread. A square thread has 90deg from the bottom to the wall. An acme thread has a 29 deg included angle. A lot of older weapons had "square" threads.
I hope you didn't cut acme threads on the Springfield as they were 10TPI square threads.

 

[GenePoole]

1903 threads are square, not acme which have a 29 degree included angle.

I believe Garand and M14/M1A use square threads as well.

 

[Cloudrepair]

I've done several dozen square threaded barrels particularly M1917's. While I don't build them like your one custom rifle, IMO, mine are nicer than 99% of them out there and they all shoot. I'll have to respectfully disagree with that statement. While the shoulder may help square the barrel, it will do nothing to center it with square threads. That's the threads job to center it, and on a square thread, they must be a tad more snug than you can get away with on standard 60 degree threads. Square threads don't self center. Tell me how two 90 degree surfaces impose anything other than 180 degree opposing forces to each other.

To go a step further if you have short threads and deep grooves on a square thread, you can easily tighten a barrel snug on the shoulder and have it not centered or concentric to the reciever.

I do know however that a correct 60 degree thread will by geometry, tighten up and self center itself. That makes perfect sense to me.

True on your last paragraph but the shoulder or barrel nut face will be the last word/ alignment.

 

[msinc]

Google is your friend. An acme thread is different than a square thread. A square thread has 90deg from the bottom to the wall. An acme thread has a 29 deg included angle. A lot of older weapons had "square" threads.
I hope you didn't cut acme threads on the Springfield as they were 10TPI square threads.

My mistake...I used a form tool so at least the rifles were right, even if I am wrong in the name.

 

[msinc]

True on your last paragraph but the shoulder or barrel nut face will be the last word/ alignment.

Usually, but with a square thread not exactly...it depends on what you are "aligning"...if we are talking about the chamber/bore centerline to the bolt face when using a square thread then it is this unthreaded portion of the tendon that "aligns" {centers} the barrel to the receiver.
If some of these guys weren't so bent on calling out a simple mistake that had little to do with the point they would have realized that I am their "friend".....for those of you that caught the mistake, thank you, I have corrected my post. Endless apologies, a thousand pardons..... See photo of Garand tenon below, sorry fellas, I don't presently have a Springfield 03 or Garand receiver to photo and post.....

 

[spitfire_er]

M1917/pattern 1914's thread right up to the shoulder, I believe 03's do as well. Been a while since I touched a Krag barrel.