I know this has been covered but i need to ask this straight forward. Since a reamer will follow the bore can you simply dial the chamber area in as close as possible and then use a dead center and a finish reamer or roughing reamer first to cut the chamber. It seems to me that what we want to do is to have the chamber true with the bore and since a reamer will follow why use a boring bar or anything else to cut the chamber? Am i thinking about this properly? Wont the reamer follow exactly what we are wanting it to with the bore? I understand that the bore must be dialed in as close as possible so that the threads and shoulder is all cut properly, but it just seems to me that cutting the chamber is pretty straight forward? Would a floating reamer holder be better than a dead center? Sorry to re hash all this out! Lee
Barrel chambering, is it as simple as??
- Thread starter skeetlee
- Start date
Lee this is perty much how chambering has been taught for 100yrs. This is how I learned it in gunsmithing school.
This is NOT how I do it today.
al
Skeetlee if you are not comfortable posting your e-mail address on this site just e-mail at johnlouis123@att.net and I would be more than happy to send the PDF article as well as Jackie Schmidt's article on how to check your work.
The PDF is titled Internet Discussion Forum & Web Articles Related To Barrel Chambering 2/3/2009 and contains 131 pages of valuable information and is a good reference to have on hand.
J.Louis
The PDF is titled Internet Discussion Forum & Web Articles Related To Barrel Chambering 2/3/2009 and contains 131 pages of valuable information and is a good reference to have on hand.
J.Louis
Skeetlee I was able to copy and past this one for you but I still can't figure out how to post the PDF.
02-07-2011
Jackie Schmidt
Try This
Forget about the "Gunsmith" thing for a minute and look at this strictly from a Machinist viewpoint.
If bores were truly straight, all of this would be a moot point, because any 1st year apprentice can indict two points.
Since bores are not "straight", (in fact, they are not even "curved', they have "kinks" in them), you have no choice but to true two points and then some way get a third point running true with those two points. From a machinist standpoint, the only way to do this is to single point bore that "third point", thus establishing three points that run dead true with the machines bearings, (ie, "true").
By establishing the muzzle end true, and then establishing a point in the bore's area that will represent the first thing that the bullet "sees" as it leaves the case neck, then single point boring the chamber so it runs dead true with these two points, you will have no problem establishing a chamber that is "true" with the barrel's ID. That is, true with the original two indicated points, heck, one inch further from those two points may show as much as .001 run out. There is nothing you can do about this, because the bore is not even straight with its own self.
How many of you actually check everything after you finish a chamber. I do. I have written this before, but for those that have not been around that long, I will repeat the process.
After you have finished your entire chamber job, and before you remove the barrel from the final set-up, here is how you check your work.
Take your long stylus indicator and reach into the bore just a fraction further than where the lead angle ends. Indicate the lands and grooves, and see how much variation you get. Then, move the indicator back until you are on the actual tapered lead, (the last thing the reamer cut). Take a reading. Then, move the indicator back to the neck portion of the chamber, then to the body of the chamber, front and back.
Then, put your lathe in what ever thread you cut, and kick the half nut in. Place the ball stylus of the indicator in the V's of the thread, roll the chuck until all slack is out and the carriage is advancing. Record the indicator reading. Then place the stylus on the shoulder of the tenon, and record any run out there.
If you get more than .0002 to .0003 on any of these, you are inducing run out somewhere in your set-up. And, until you actually check your work, and see, you are simply relying on your set-up to be correct.
Of course, I am well aware that many of the lathes that Gunsmiths and Hobbyist use for their work are not even capable of producing this type of accuracy. Which leads us to this point. How accurate does all of this have to be? I have checked barrels done by others, and in my opinion, they never actually check their finished job because I get quite a bit of run out when checking the various fits against the others. These barrels shot great.
Sorry, but I tend to look at everything from a Machinist viewpoint. In my world, the only thing that counts is the finished job. Of course, you do have to have a means of performing operations that are within the capabilities of your shop, and of course, your budget And, you have to be willing to check your set-ups and correct any procedures that will cause the finished piece to be less than satisfactory when subjected to final inspection.
In my opinion, many of our "gunsmiths", and "machinist" in general, are simply "painting by the numbers". Change any part of the equation, and they have no way of knowing how to modify the operation to correct the flaws that can show up in the final inspection........Jackie
Last edited by Jackie Schmidt; 02-07-2011 at 09:29 AM.
02-07-2011
Jackie Schmidt
Try This
Forget about the "Gunsmith" thing for a minute and look at this strictly from a Machinist viewpoint.
If bores were truly straight, all of this would be a moot point, because any 1st year apprentice can indict two points.
Since bores are not "straight", (in fact, they are not even "curved', they have "kinks" in them), you have no choice but to true two points and then some way get a third point running true with those two points. From a machinist standpoint, the only way to do this is to single point bore that "third point", thus establishing three points that run dead true with the machines bearings, (ie, "true").
By establishing the muzzle end true, and then establishing a point in the bore's area that will represent the first thing that the bullet "sees" as it leaves the case neck, then single point boring the chamber so it runs dead true with these two points, you will have no problem establishing a chamber that is "true" with the barrel's ID. That is, true with the original two indicated points, heck, one inch further from those two points may show as much as .001 run out. There is nothing you can do about this, because the bore is not even straight with its own self.
How many of you actually check everything after you finish a chamber. I do. I have written this before, but for those that have not been around that long, I will repeat the process.
After you have finished your entire chamber job, and before you remove the barrel from the final set-up, here is how you check your work.
Take your long stylus indicator and reach into the bore just a fraction further than where the lead angle ends. Indicate the lands and grooves, and see how much variation you get. Then, move the indicator back until you are on the actual tapered lead, (the last thing the reamer cut). Take a reading. Then, move the indicator back to the neck portion of the chamber, then to the body of the chamber, front and back.
Then, put your lathe in what ever thread you cut, and kick the half nut in. Place the ball stylus of the indicator in the V's of the thread, roll the chuck until all slack is out and the carriage is advancing. Record the indicator reading. Then place the stylus on the shoulder of the tenon, and record any run out there.
If you get more than .0002 to .0003 on any of these, you are inducing run out somewhere in your set-up. And, until you actually check your work, and see, you are simply relying on your set-up to be correct.
Of course, I am well aware that many of the lathes that Gunsmiths and Hobbyist use for their work are not even capable of producing this type of accuracy. Which leads us to this point. How accurate does all of this have to be? I have checked barrels done by others, and in my opinion, they never actually check their finished job because I get quite a bit of run out when checking the various fits against the others. These barrels shot great.
Sorry, but I tend to look at everything from a Machinist viewpoint. In my world, the only thing that counts is the finished job. Of course, you do have to have a means of performing operations that are within the capabilities of your shop, and of course, your budget And, you have to be willing to check your set-ups and correct any procedures that will cause the finished piece to be less than satisfactory when subjected to final inspection.
In my opinion, many of our "gunsmiths", and "machinist" in general, are simply "painting by the numbers". Change any part of the equation, and they have no way of knowing how to modify the operation to correct the flaws that can show up in the final inspection........Jackie
Last edited by Jackie Schmidt; 02-07-2011 at 09:29 AM.
Had a teacher in Jr High, that was giving a safety briefing on band saw. He then proceeded to slice his thumb off in front of the class. After turn the saw off, he calmly picked up the severed thumb and wrapped it in his handkerchief and call a sub in. He was in class the next day, but wasn't giving any more safely instructions to the class. Shop class went on without another injury to students or teachers, the rest of the year.
J
My email is gleegardner@yahoo.com
My email is gleegardner@yahoo.com
jackie schmidt
New member
Skeet, even if I had not written this, I would say it is true and to the point.
Many fear actually subjecting their work to a rigorous inspection because they have no idea how to fix any problems that the inspection might bring to light.
Many fear actually subjecting their work to a rigorous inspection because they have no idea how to fix any problems that the inspection might bring to light.
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Very, very good post Jackie.
It should probably be re-posted at least once year (or as needed), and twice as often in the winter months.
Thanks.
Edit:
Maybe now we can get people to stop talking about "the perfect way to chamber" and say why they pick the two points they do to set up on. I know why I choose the ones I do, but in the end, it's just reasoning that may be spurious.
It should probably be re-posted at least once year (or as needed), and twice as often in the winter months.
Thanks.
Edit:
Maybe now we can get people to stop talking about "the perfect way to chamber" and say why they pick the two points they do to set up on. I know why I choose the ones I do, but in the end, it's just reasoning that may be spurious.
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Boyd Allen
Active member
Lee,
The reason that many do not use a dead center in the tail stock to push their reamers is that it is common for the center of a tail stock to be misaligned with the center of the spindle, and although left to right adjustment is a typical feature, up and down is much more involved. Any amount that the dead center is off from the center of the headstock spindle will enlarge the rear of the chamber by twice the offset, measured on that part of the reamer where the back of the chamber will be cut, which will be somewhat less than the measurement at the tip of the dead center, assuming you have indicated the barrel where the reamer pilot will be when the chamber is at full depth. The fellow that chambers my barrels gets around this problem by mounting a dead center on the tool post, which allows him to adjust its position relative to the spindle center of rotation both horizontally and vertically. Also, there are advantages to preboring, beyond reduction of finish reamer wear, especially when a pusher or floating holder are used.
Boyd
The reason that many do not use a dead center in the tail stock to push their reamers is that it is common for the center of a tail stock to be misaligned with the center of the spindle, and although left to right adjustment is a typical feature, up and down is much more involved. Any amount that the dead center is off from the center of the headstock spindle will enlarge the rear of the chamber by twice the offset, measured on that part of the reamer where the back of the chamber will be cut, which will be somewhat less than the measurement at the tip of the dead center, assuming you have indicated the barrel where the reamer pilot will be when the chamber is at full depth. The fellow that chambers my barrels gets around this problem by mounting a dead center on the tool post, which allows him to adjust its position relative to the spindle center of rotation both horizontally and vertically. Also, there are advantages to preboring, beyond reduction of finish reamer wear, especially when a pusher or floating holder are used.
Boyd
N
NFG
Guest
I have a few observations reguarding chambering...I'm NOT either a gunsmith OR a machinist, but I've been building rifles since the late 50's...and almost all of them will shoot quarter inch 5 shot groups once I build the ammo and rifle as a system.
Jackie made the point that barrels are "KINKY" which is totally true...lands and grooves wiggle and squirm all over the place in relation to the bore centerline, from one end to the other AND themselves within a small variation of ~0.001-0.002", even in the better barrels. Lathes have more wiggle and squirm than a bucket of snakes from headstock bearings to lead screws to way wear and stiction, to tailstock mis-alignment and thread/tube/center wear, to flex in the spinning barrel during chamber cutting and threading.
The average gunsmith can control only a few of those variations and even though you might be able to dial in one small section to a couple of tenths to a few millions, you CAN'T maintain that over the length of a barrel even if you have the most expensive, most perfetct CNC lathe in the world.
I'm not dissing anyone or flaming, or any of that kind of crap...this is my thoughts and observations over these many years...
There is "theoretical perfection" and "real world application of reality"...it totally amazes me every time I do a barrel and measure the actual TIR of the chamber, the threads, the receiver then actually work up a good load that shoots bugholes for a time at least. These are NOT benchrest/target level guns, I've been out of that for 30 years, but when conditions are right and I'm "on" I can shoot groups that would have won many a benchrest match in the bad old days.
I've just about concluded that the chamber end is only part of the equation and what happens in the last few inches of the barrel and when the bullet exits is of more import...as long as the chamber is on centerline and starts the bullet off fairly concentric the last few inches of the barrel is what finally gets the bullet on path...and that requires a high quality, lapped barrel so that "kinkyness" has been reduced to a minimum.
Most of the better barrels that I read about these days keep variation down to 5 tenths or so...which is still 0.001" TIR...if that is so and the floating pilot fits to a tenth and the tailstock is perfectly aligned so there is no wobbling out of the base end, and the machine has NO variation or runout, then the best alignment and least amount of run out is still what is inherent in the barrel variation...Theoretically speaking...hardly any of this happens in the real world.
Which is still pretty amazing considering what was available in yesteryear.
My other observation is...you need to keep perspective running at all times...what is required to keep in the winners circle in benchrest and long range target is much different that what is required to keep the freezer full of meat...and most shooters pocket books are relatively shallow...which is why most rifles are built to a relatively low level of cost and quality in ALL the aspects from nuts to bolts to barrels and machining...who can afford "the perfect rifle"?
But deep thinking is always a good thing...stretches out the envelope and brings up new and interesting questions and opens new roads.
Luck
Jackie made the point that barrels are "KINKY" which is totally true...lands and grooves wiggle and squirm all over the place in relation to the bore centerline, from one end to the other AND themselves within a small variation of ~0.001-0.002", even in the better barrels. Lathes have more wiggle and squirm than a bucket of snakes from headstock bearings to lead screws to way wear and stiction, to tailstock mis-alignment and thread/tube/center wear, to flex in the spinning barrel during chamber cutting and threading.
The average gunsmith can control only a few of those variations and even though you might be able to dial in one small section to a couple of tenths to a few millions, you CAN'T maintain that over the length of a barrel even if you have the most expensive, most perfetct CNC lathe in the world.
I'm not dissing anyone or flaming, or any of that kind of crap...this is my thoughts and observations over these many years...
There is "theoretical perfection" and "real world application of reality"...it totally amazes me every time I do a barrel and measure the actual TIR of the chamber, the threads, the receiver then actually work up a good load that shoots bugholes for a time at least. These are NOT benchrest/target level guns, I've been out of that for 30 years, but when conditions are right and I'm "on" I can shoot groups that would have won many a benchrest match in the bad old days.
I've just about concluded that the chamber end is only part of the equation and what happens in the last few inches of the barrel and when the bullet exits is of more import...as long as the chamber is on centerline and starts the bullet off fairly concentric the last few inches of the barrel is what finally gets the bullet on path...and that requires a high quality, lapped barrel so that "kinkyness" has been reduced to a minimum.
Most of the better barrels that I read about these days keep variation down to 5 tenths or so...which is still 0.001" TIR...if that is so and the floating pilot fits to a tenth and the tailstock is perfectly aligned so there is no wobbling out of the base end, and the machine has NO variation or runout, then the best alignment and least amount of run out is still what is inherent in the barrel variation...Theoretically speaking...hardly any of this happens in the real world.
Which is still pretty amazing considering what was available in yesteryear.
My other observation is...you need to keep perspective running at all times...what is required to keep in the winners circle in benchrest and long range target is much different that what is required to keep the freezer full of meat...and most shooters pocket books are relatively shallow...which is why most rifles are built to a relatively low level of cost and quality in ALL the aspects from nuts to bolts to barrels and machining...who can afford "the perfect rifle"?
But deep thinking is always a good thing...stretches out the envelope and brings up new and interesting questions and opens new roads.
Luck
Boyd Allen
Active member
Good post
J
JLDavid
Guest
skeetlee,
Could you email me that article on chambering the you received? My email is jace@centurytel.net Thanks
Could you email me that article on chambering the you received? My email is jace@centurytel.net Thanks
Since the PDF is on the internet, all you have to do is find a link that has it, and open it. It's big, so takes a while to open. Now, you can save it to your machine, print it out -- both -- whatever.
Here is one link with the PDF:
http://hotrodgossip.org/fogger/CHAMBERING.pdf
Here is one link with the PDF:
http://hotrodgossip.org/fogger/CHAMBERING.pdf
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F
Fishoot
Guest
Chambering Information
I would like to read your PDF too. Please email to: tomcarla@att.net. Sorry if its becomming a job replying to all of these. Thanks, Tom
I would like to read your PDF too. Please email to: tomcarla@att.net. Sorry if its becomming a job replying to all of these.
Thanks, TomSee post 17, this thread. It can be in your hands in minutes, with no hassle for anyone else.I would like to read your PDF too. Please email to: tomcarla@att.net. Sorry if its becomming a job replying to all of these.