It seems like there's been a bit of talk around here about barrel threading recently and I've been thinking of offering something to those just starting out that I learned the hard way.
Here's what happened to me the first time I threaded a barrel. It was for a Savage, an older long action. I hopped on the internet and got the thread spec. The Internet said it is 1.055x20. Went on my favorite engineering site, and as 1.055x20 is not a standard size but 1 1/16 is, I got the major diameter and pitch diameter for 1 1/16x20 and figured I'd be safe, the worst that would happen is that I would be oversize for the 1.055 and could cut the thread a little deeper as needed. I proceeded to cut a nearly perfect thread and nailed the maximum pitch diameter right on the nose. Proud of my work, I tried the action to see if I needed to cut more, and found the action was already looser than I would have liked!
Since then I cut my tenon about 7 or 8 thousandths over, cut my thread until it gets close to looking like a finished thread and start trying the action for fit. I basically cut little by little until the action fits the thread as I like. If I then measure the thread I find it's over spec for pitch diameter. Seems the firearms industry, and least in the past, kinda did their own thing.
All this to say, cut your thread to fit your action, not to any certain specification.
Watch your thread peaks, knock them down with a file even to the point where you begin to see tiny flats start to appear on the peaks. It's easy to get a major diameter too big because a. you started out 7-8 thou over and b. sometimes a small amount material displaces up and out of the thread instead of being cut away...it shouldn't if you're doing it right sometimes it does, especially with stainless.
So that's my advice. Keep in mind I'm a guy doing his own work and have all the time in the world to do the job. Professionals or those with more experience will no doubt have a better way. I just hope nobody comes on here and tells me I'm full of baloney. This is what works for me. I guess the best thing is to learn under the tutelage of an experienced gunsmith but most of us don't have that opportunity. Before I began my first rebarrel I did go and ask some questions in the gunsmith forum of widely known, very big machining forum. I quickly learned newbies and their basic questions would not be tolerated. So, off I went to discover my own way! I suppose many of us have done the same.
edit to add, accidentally posted before I was ready. I was going to trim it down and make it more concise but...there it is.
Here's what happened to me the first time I threaded a barrel. It was for a Savage, an older long action. I hopped on the internet and got the thread spec. The Internet said it is 1.055x20. Went on my favorite engineering site, and as 1.055x20 is not a standard size but 1 1/16 is, I got the major diameter and pitch diameter for 1 1/16x20 and figured I'd be safe, the worst that would happen is that I would be oversize for the 1.055 and could cut the thread a little deeper as needed. I proceeded to cut a nearly perfect thread and nailed the maximum pitch diameter right on the nose. Proud of my work, I tried the action to see if I needed to cut more, and found the action was already looser than I would have liked!
Since then I cut my tenon about 7 or 8 thousandths over, cut my thread until it gets close to looking like a finished thread and start trying the action for fit. I basically cut little by little until the action fits the thread as I like. If I then measure the thread I find it's over spec for pitch diameter. Seems the firearms industry, and least in the past, kinda did their own thing.
All this to say, cut your thread to fit your action, not to any certain specification.
Watch your thread peaks, knock them down with a file even to the point where you begin to see tiny flats start to appear on the peaks. It's easy to get a major diameter too big because a. you started out 7-8 thou over and b. sometimes a small amount material displaces up and out of the thread instead of being cut away...it shouldn't if you're doing it right sometimes it does, especially with stainless.
So that's my advice. Keep in mind I'm a guy doing his own work and have all the time in the world to do the job. Professionals or those with more experience will no doubt have a better way. I just hope nobody comes on here and tells me I'm full of baloney. This is what works for me. I guess the best thing is to learn under the tutelage of an experienced gunsmith but most of us don't have that opportunity. Before I began my first rebarrel I did go and ask some questions in the gunsmith forum of widely known, very big machining forum. I quickly learned newbies and their basic questions would not be tolerated. So, off I went to discover my own way! I suppose many of us have done the same.
edit to add, accidentally posted before I was ready. I was going to trim it down and make it more concise but...there it is.
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