Barrel blank-threading/chambering question

I got a Bartlein blank and am going to be threading it next week for 6.5CM. I have the older small shank action ('97 10FP). Looking for any info from anyone who has done this before. I found that my action is threaded 1.055x20tpi. Being that its an oddball thread do I just turn it 1.055 and thread or should I go lower like most threads listed in the Machinery Handbook? I plan on measuring the factory barrel when I get it off to reverse engineer and thread some steel to make a plug gauge but I'm looking for a place to start so I don't waste time. Any help is appreciated.

And I'm doing away with the barrel nut in case your are wondering....not that I want to get into that discussion. I'm going to face the action as well but leave the rest alone. Might lap the lugs since they aren't making correct contact prior to chambering.

Face the action with respect to the threads not the bolt raceway.

Many have found with pre-fits that the action threads are not fully formed. They have to knock the peaks of the barrel threads off to mate to the acton. Use the major diameter of your take off barrel as a good reference as to where you need to be.

If you have some thread inspection wires you can check the pitch diameter on an existing barrel with them. Then duplicate that dimension. I believe it is 1/16 thread pitch diameter just about .0035 per side smaller on the major diameter.

http://cloudfront.zorotools.com/prod...5RCJ7_AS01.JPG

Why would I want to face with respect to the action threads? Won't that put my barrel off if the threads are off. I might touch the threads up anyway but I won't know until I get it apart.

I got the wires and that was what I planeed on doing. I guess I'm basically looking for an actual number of what people have done it the past. If someone made a plug gauge what size was it so I have something to compare to?

Have you ever fit a barrel to an action? Cut a chamber? or done anything of the sorts?

No but I've cut plenty of threads and reamed a bunch of holes. That sounded weird. First time on a barrel though. Why?

Based on how you asked the questions it seemed like you have never done it before. For a first timer it would be easier to cut a barrel with the barrel nut.

You almost finished your point sin...I'm left hanging. Cut a barrel thread with a die or cut the thread with the barrel nut?
:behindsofa:

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Originally Posted by stangfish

You almost finished your point sin...I'm left hanging. Cut a barrel thread with a die or cut the thread with the barrel nut?
:behindsofa:

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All the barrel threads I have cut have been with a lathe and threading tool.....

http://i747.photobucket.com/albums/x...ps75878e81.gif

and I agree with sinman, ffor a first timer I would go with a thread that uses the nut over the shoulder.

If yer a first timer......ya might wanna practice on some scrap first. Keep cuttin' threads till the action screws on.

Thanks for the replies. I'm not asking about how to thread a barrel and even though it is my first time I have done my research, practiced on blanks, etc, etc....I've been using a lathe for many years, taken classes and understand threading and never had a problem with it. I've taken the steps need to prepare myself for my first barrel and really it doesn't seem all that much different than all the other stuff I have threaded other than I need to be spot on for obvious reasons.

My question was pertaining to finding the pitch diameter, major diameter, minor diameter, etc for the thread on my action or Savage actions in general since so much information out there is for Remmys. I know how I want to do it and I'm going to make a plug gauge first. I was just hoping someone here could share their way (which hopefully coincided with the way I was thinking) and some specs to work off of before I go taking mine apart and figuring it out for myself.

Let me ask this. I have seen the 1.055-20 posted a lot of places. Is the 1.055 the real major diameter I would turn to (in theory) before I started the threading process? For instance a 1/2-20 thread, depending on thread class, can have a major diameter of .500 to maybe .489 and still be a 1/2-20. I'm just not used to seeing the "1.055" or is it really considered a 1-1/16 - 20? Either way when I get it apart I can figure it out so I guess its not a big deal. And I understand every action is different so I need to cut it to my action.

You guys are right..threading for a barrel nut would be much easier but I'm not going that route. It certainly has its benefits but its not getting cut like that. The next Savage I do probably will be with a nut so I can swap barrels....not needed this time around.

I turn my barrels to 1.06 before I thread them. The major diameter of the threads is 1 1/16, which is 1.062, but most people cut the major diameter small, which leaves flat spots on top of the threads, I am unsure of why that is the standard.

I would suggest for threading that you use a 4 jaw and indicate the barrel in off the bore(ID), then turn the barrel down to size and thread. That's how I prefer to do it when I am putting a barrel on a specific action; that way once you think you might be close, you can take the action and see if it screws onto the threads your cutting or not. Even though there are specific sizes that a thread is suppose to be, I have seen quite a bit of variation on the thread sizes.

I have seen savages both with and without barrel nuts. If you are planning on making the barrel shoulder up on the action you need to make sure you have a way to torque the action against the shoulder. While for a first timer I would agree it would be easier to machine the barrel and retain the barrel nut system, for ease of head spacing, that's not how I learned

Start with a major of 1.06 and work in, testing on your action as you go, but almost all of mine have ended up +/- .001 of the 1.055 diameter. Sounds like you have prior expereince doing machine work, so go with what you feel confident.

I'm in the same position currently, I can get the blank I need but have to find someone to profile, chamber and crown it, as well as machine the breech end. Mine is for a Remington, but I was going to get the Remington barrel nut from NSS, that makes it an easier job than the conventional breeching method.

I just took my lathe bed to a specialist grinding shop to have the ways ground so by the end of the year I should have my own 14"x60 heavy lathe operational. Then its just a matter of tooling.....

Something I am eternally curious about, in this day and age of CNC machines: Why are chambers and throats not simply cut with boring bars ? Or at least roughed out that way ? I have never seen a chamber being rough reamed but I have to imagine that it is a slow cut ? Whereas a carbide boring bar would speed it up drastically ? I had some custom carbide boring bars made which were able to turn a cone into a 0.008" diameter hole, leaving the diameter of the hole undisturbed. You need a magnifying glass to even see the end of the bar, the shank was less than 1/8".

Because sometimes "old School" is better. I haven't single pointed a barrel thread in years, since I got a geometric die head. Once it is set, it will cut threads to the same dimensions every time and it only takes 25 seconds a pass, in 2 passes.

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Originally Posted by sharpshooter

Because sometimes "old School" is better. I haven't single pointed a barrel thread in years, since I got a geometric die head. Once it is set, it will cut threads to the same dimensions every time and it only takes 25 seconds a pass, in 2 passes.

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Now THAT is cool!!!

I didn't ask the question about threading, I asked why chambers and throats could not be single point cut in a CNC machine ? Or do all smiths use manual machines, including the barrel makers ? I/m pretty sure any barrel maker today who cuts the thread as part of the profiling operation is using a single point tool in a CNC. A guy working from a blank on a manual machine, different story.

Savage cuts threads in the profiling operation on a Mori Seiki CNC turning center with a single point tool. The threads are cut in 7 passes. I can't say it's more consistent, because it is not. I've measured thread shanks on hundreds of take off barrels and found that the tolerance is quite wide....wider than than what's on their own prints.

As far as chambering with a boring bar, that has been tryed with no success. It's harder to hold a dimension in a production scale that is required for that specific operation. And by the way...Savage does not chamber their barrels on a lathe.

I suppose I should have qualified "barrel makers" as those besides the rifle makers. I get the impression that plenty of dodgy tactics are used by Remington, Savage and others in making parts for their rifles. However, in the field of precision machining, hardly anything gets made with a reamer unless it is a straight bore or a defined taper. Virtually everything is cut with a single point tool. Down to 2/10 000th tolerances too, so to tighter specs than the manufacturers actually hold on their reamed chambers.

What kind of variation did you see on the barrel threads ? Too large/small, tapered or what ? Unless the machinist keeps his machine / insert dialed in, clearly there will be a bunch of variation. Thats the point of statistical process control, to identify the sources of variation and then define periodic maintenance so that the source is eliminated or fixed before anything gets out of spec. Sounds like these guys live in a world prior to ISO 9000 or even plain good management.

If a guy like you ever toured the Savage plant prior to 2008, you would **** your pants at the way they were doing things and the things they got away with. When I toured the plant in Nov of '05, they used several Mori Seiki turning centers to do strickly barrel work. It would turn, thread and crown a sporter barrel from 1.110" rifled blank in 2.5 minutes. At the time, this was their newest machines. Other than that, they had a total of 3 CNC mills doing receiver operations, the oldest being a Bostomatic purchased in 1988. The rest were done on an assortment of (about 50) Cinncinnati horizontal mills set up for just 1 operation.
Barrels were chambered on a Byrd vertical turret mill. The barrel is stationary, the tools turn. 1st op is a chamfer tool, 2 is a core drill, 3 is a rougher reamer, 4 is a finish reamer, and the last is a flexi-hone which does 20 peck cycles. Amazingly, the chambers come out very consistent in size, but they may not be centered in the bore. They retired those machines 2 years ago, and replaced them with new machines of the same type. When I asked the director of engineering why they did not go with HMC's he stated that they could not get the results they could with the vertical machines.