How I would deepen a chamber?

Bill Calfee

Gun Fool
How I would deepen a chamber?


CYA friends:


Even though I doubt I have much influence with the Almighty, I'd start deepening a chamber with a prayer.


Cause it's so difficult to do perfectly.



_____________________________


Chambering using a reamer:

(For folks who bore chambers, one of them will have to describe the process.)




The main problem with trying to deepen a finished chamber, is that, when the chamber is slightly enlarged by the finishing process the reamer flutes lose their support.



Therefore..........................



The reamer has to be totally guided by the pilot, only.

____________________________


Before I proceed, I do not use tight fitting pilots, for a reason.


Taper lapped bores seldom remain truly round land top to land top, at the breech end, even if the "as buttoned" blank was perfect to begin with.


This is just the nature of taper lapping, since most of the lapping strokes are at the breech end of the blank.


And of course a reamer pilot, pilots off of the land tops.



Here's the reason I do not use tight fitting pilots:


The beauty of using a reamer to cut a chamber, is that, the reamer will "center on the distorted mass" at the breech end of the blank, if, you give it its head.


In other words if left alone, the reamer will find the best "compromise of location" to center the chamber on the slightly "out of round" land tops.



And keep something in mind here:


If a bore is properly taper lapped, the lands and grooves, although slightly out of round at the breech end of a blank, will be out of round together.




( This is why I don't believe I could bore a chamber, because how does one indicate an out of round bore/groove situation that exists in most taper lapped barrels?)


So a reamer, if left alone, will do the best job of compromising the proper location for the chamber, in a taper lapped blank.



____________________________


But.......................



Deepening a finished chamber is a different story.


The pilot has to do all the centering, since the flutes have lost their support.




_______________________



If I had to deepen a chamber, here's what I'd do:



I would use a tight fitting pilot......even if I had to make one special.


Keep something in mind here:



There's clearance between the OD of the pilot and the land tops...


Plus, there's clearance between the OD of the pilot shaft of the reamer and the ID of the pilot itself.



Therefore, I'd remove the pilot, clean the the ID of it and the OD of the pilot shaft of the reamer, with mineral spirits, this since I use lard oil to chamber with, and mineral spirits reduces lard oil.


Then thoroughly dry both the pilot and reamer.


Then I'd apply cup grease to the ID of the pilot and OD of the pilot shaft of the reamer.......then put the pilot back on the shaft and rotate it, and slide it on and off the shaft until the cup grease was thoroughly distributed.


Then I'd re-install the pilot retaining clip, or screw, and wipe off the excess cup grease with a clean paper towel.


Then the reamer goes into the refrigerator until the moment I'm ready to deepen the chamber.




(I'm only going to deepen the chamber a few thousandths, so one pass is all that should be necessary.)



What this process with the cup grease getting cold does, is to completely eliminate the clearance between the pilot and reamer.


No, the pilot will no longer rotate when you deepen the chamber, which means nothing as far as scratching the land tops...


Properly used, a solid pilot reamer will not damage the land tops any more than a floating pilot reamer.


____________________________



I'd have the barrel completely set up and everything ready to go, then at that moment I'd get the reamer out of the refrigerator, and do the deed.


Your friend, Bill Calfee



___________________________


PS:


There would be one advantage to deepening a chamber by boring, that is, the existing chamber could be indicated off of.


Exactly how the boring bar would be handled, in such a way, as to keep from ringing the chamber when starting the cut, I don't know.


If someone who bores chambers would care to comment, please feel free to do so....
 
Last edited:
How I would deepen a chamber?


CYA friends:


Even though I doubt I have much influence with the Almighty, I'd start deepening a chamber with a prayer.


Cause it's so difficult to do perfectly.



_____________________________


Chambering using a reamer:

(For folks who bore chambers, one of them will have to describe the process.)




The main problem with trying to deepen a finished chamber, is that, when the chamber is slightly enlarged by the finishing process the reamer flutes lose their support.



Therefore..........................



The reamer has to be totally guided by the pilot, only.

____________________________


Before I proceed, I do not use tight fitting pilots, for a reason.


Taper lapped bores seldom remain truly round land top to land top, at the breech end, even if the "as buttoned" blank was perfect to begin with.


This is just the nature of taper lapping, since most of the lapping strokes are at the breech end of the blank.


And of course a reamer pilot, pilots off of the land tops.



Here's the reason I do not use tight fitting pilots:


The beauty of using a reamer to cut a chamber, is that, the reamer will "center on the distorted mass" at the breech end of the blank, if, you give it its head.


In other words if left alone, the reamer will find the best "compromise of location" to center the chamber on the slightly "out of round" land tops.



And keep something in mind here:


If a bore is properly taper lapped, the lands and grooves, although slightly out of round at the breech end of a blank, will be out of round together.




( This is why I don't believe I could bore a chamber, because how does one indicate an out of round bore/groove situation that exists in most taper lapped barrels?)


So a reamer, if left alone, will do the best job of compromising the proper location for the chamber, in a taper lapped blank.



____________________________


But.......................



Deepening a finished chamber is a different story.


The pilot has to do all the centering, since the flutes have lost their support.




_______________________



If I had to deepen a chamber, here's what I'd do:



I would use a tight fitting pilot......even if I had to make one special.


Keep something in mind here:



There's clearance between the OD of the pilot and the land tops...


Plus, there's clearance between the OD of the pilot shaft of the reamer and the ID of the pilot itself.



Therefore, I'd remove the pilot, clean the the ID of it and the OD of the pilot shaft of the reamer, with mineral spirits, this since I use lard oil to chamber with, and mineral spirits reduces lard oil.


Then thoroughly dry both the pilot and reamer.


Then I'd apply cup grease to the ID of the pilot and OD of the pilot shaft of the reamer.......then put the pilot back on the shaft and rotate it, and slide it on and off the shaft until the cup grease was thoroughly distributed.


Then I'd re-install the pilot retaining clip, or screw, and wipe off the excess cup grease with a clean paper towel.


Then the reamer goes into the refrigerator until the moment I'm ready to deepen the chamber.




(I'm only going to deepen the chamber a few thousandths, so one pass is all that should be necessary.)



What this process with the cup grease getting cold does, is to completely eliminate the clearance between the pilot and reamer.


No, the pilot will no longer rotate when you deepen the chamber, which means nothing as far as scratching the land tops...


Properly used, a solid pilot reamer will not damage the land tops any more than a floating pilot reamer.


____________________________



I'd have the barrel completely set up and everything ready to go, then at that moment I'd get the reamer out of the refrigerator, and do the deed.


Your friend, Bill Calfee



___________________________


PS:


There would be one advantage to deepening a chamber by boring, that is, the existing chamber could be indicated off of.


Exactly how the boring bar would be handled, in such a way, as to keep from ringing the chamber when starting the cut, I don't know.


If someone who bores chambers would care to comment, please feel free to do so....

Howdy Bill,

Very informative post! I’ve read this at least three times, spaced out over a little time, and picked up several different things with each reading.

I have to ask this because I just don’t know. When the reamer goes in the refrigerator, does it get cold enough to shrink it a little? Would it be advantageous to get the barrel cold, too? Would it even be possible to get the barrel set up in the lathe fast enough to have it near the same temperature as the reamer?

I’m just trying to figure out if the temperature would affect the size of the cut.

Take care,

Greg
 
Last edited:
Friend 404tbang

How I would deepen a chamber?


CYA friends:


Even though I doubt I have much influence with the Almighty, I'd start deepening a chamber with a prayer.


Cause it's so difficult to do perfectly.



_____________________________


Chambering using a reamer:

(For folks who bore chambers, one of them will have to describe the process.)




The main problem with trying to deepen a finished chamber, is that, when the chamber is slightly enlarged by the finishing process the reamer flutes lose their support.



Therefore..........................



The reamer has to be totally guided by the pilot, only.

____________________________


Before I proceed, I do not use tight fitting pilots, for a reason.


Taper lapped bores seldom remain truly round land top to land top, at the breech end, even if the "as buttoned" blank was perfect to begin with.


This is just the nature of taper lapping, since most of the lapping strokes are at the breech end of the blank.


And of course a reamer pilot, pilots off of the land tops.



Here's the reason I do not use tight fitting pilots:


The beauty of using a reamer to cut a chamber, is that, the reamer will "center on the distorted mass" at the breech end of the blank, if, you give it its head.


In other words if left alone, the reamer will find the best "compromise of location" to center the chamber on the slightly "out of round" land tops.



And keep something in mind here:


If a bore is properly taper lapped, the lands and grooves, although slightly out of round at the breech end of a blank, will be out of round together.




( This is why I don't believe I could bore a chamber, because how does one indicate an out of round bore/groove situation that exists in most taper lapped barrels?)


So a reamer, if left alone, will do the best job of compromising the proper location for the chamber, in a taper lapped blank.



____________________________


But.......................



Deepening a finished chamber is a different story.


The pilot has to do all the centering, since the flutes have lost their support.




_______________________



If I had to deepen a chamber, here's what I'd do:



I would use a tight fitting pilot......even if I had to make one special.


Keep something in mind here:



There's clearance between the OD of the pilot and the land tops...


Plus, there's clearance between the OD of the pilot shaft of the reamer and the ID of the pilot itself.



Therefore, I'd remove the pilot, clean the the ID of it and the OD of the pilot shaft of the reamer, with mineral spirits, this since I use lard oil to chamber with, and mineral spirits reduces lard oil.


Then thoroughly dry both the pilot and reamer.


Then I'd apply cup grease to the ID of the pilot and OD of the pilot shaft of the reamer.......then put the pilot back on the shaft and rotate it, and slide it on and off the shaft until the cup grease was thoroughly distributed.


Then I'd re-install the pilot retaining clip, or screw, and wipe off the excess cup grease with a clean paper towel.


Then the reamer goes into the refrigerator until the moment I'm ready to deepen the chamber.




(I'm only going to deepen the chamber a few thousandths, so one pass is all that should be necessary.)



What this process with the cup grease getting cold does, is to completely eliminate the clearance between the pilot and reamer.


No, the pilot will no longer rotate when you deepen the chamber, which means nothing as far as scratching the land tops...


Properly used, a solid pilot reamer will not damage the land tops any more than a floating pilot reamer.


____________________________



I'd have the barrel completely set up and everything ready to go, then at that moment I'd get the reamer out of the refrigerator, and do the deed.


Your friend, Bill Calfee



___________________________


PS:


There would be one advantage to deepening a chamber by boring, that is, the existing chamber could be indicated off of.


Exactly how the boring bar would be handled, in such a way, as to keep from ringing the chamber when starting the cut, I don't know.


If someone who bores chambers would care to comment, please feel free to do so....


___________________________



Friend 404tbang:


Your excellent question about cooling the reamer in the refrigerator and changing its size.


Cooling a reamer from 70 degrees down to 40 degrees would probably change the diameter of the reamer, although, I'm not sure I could measure it accurately.


If the cup grease used had the proper viscosity, cooling it probably wouldn't be necessary.


Greg, deepening a chamber that's finished is so difficult to do, and keep from making the chamber too large or mis-aligning it, that every bit of clearance possible has to be removed from the pilot/land top relationship to have the best chance for success.


Excellent question.


Your friend, BC
 
Last edited:
Calfee, you're making way too much of this

Calfee, you're making way too much of this



Calfee, man, you're making way too much of how difficult it is to deepen a finished rimfire chamber, and keep it perfectly centered and not oversized!




No I ain't, matter of fact, I ain't emphasizing it enough.



Your friend, BC


___________________________



PS:



I'll bet anyone on Earth a ten dollar bill that 50%, or more, of the chambers in RFBR guns being shot today have mis-aligned chambers, to some degree.

 

___________________________



Friend 404tbang:


Your excellent question about cooling the reamer in the refrigerator and changing its size.


Cooling a reamer from 70 degrees down to 40 degrees would probably change the diameter of the reamer, although, I'm not sure I could measure it accurately.


If the cup grease used had the proper viscosity, cooling it probably wouldn't be necessary.


Greg, deepening a chamber that's finished is so difficult to do, and keep from making the chamber too large or mis-aligning it, that every bit of clearance possible has to be removed from the pilot/land top relationship to have the best chance for success.


Excellent question.


Your friend, BC

Howdy Bill,

Thank you for the kind words. Your post inspired a bunch of questions and things to ponder. I’m still getting info from it, and not just about your clever solution to the problem.

I want to learn this stuff, thank you for being willing to post things that are so helpful!

Take care,

Greg
 
Friend 404tbang

Howdy Bill,

Thank you for the kind words. Your post inspired a bunch of questions and things to ponder. I’m still getting info from it, and not just about your clever solution to the problem.

I want to learn this stuff, thank you for being willing to post things that are so helpful!

Take care,

Greg


________________________



Friend 404tbang:


Allow me to ask you something, please........


I've advised you, Wally, Big Dog and WLB about the potential problem that may arise for the new ARA "factory" class, because of the way the rules are currently written.


Should I discuss this issue here on CYA?


Or.........................



Forget it, and let ARA deal with the consequences, should it happen, down the road?


Your friend, BC
 
Last edited:


________________________



Friend 404tbang:


Allow me to ask you something, please........


I've advised you, Wally, Big Dog and WLB about the potential problem that may arise for the new ARA "factory" class, because of the way the rules are currently written.


Should I discuss this issue here on CYA?


Or.........................



Forget it, and let ARA deal with the consequences, should it happen, down the road?


Your friend, BC

Howdy Bill,

I think this is too important to NOT discuss. It’s going to happen, especially with the rules written in such a way as to “hide the crime”. And that’s exactly what the rules will allow, as currently written. It’s an oversight that must be addressed by those making the rules. I don’t think they will know to address it until you point it out.

You made a point last week that I had not thought about. Anyone who does that one thing that “covers the crime”, regardless of whether or not they did “the crime”, WILL be accused of it if they start winning.

Yes Bill, this is something you should talk about. Please, do it. You’ll do people a favor, and it’ll even save those writing the rules a ton of headaches when they realize how this one rule can cause so many problems.

Take care,

Greg
 
Friend 404tbang

Howdy Bill,

I think this is too important to NOT discuss. It’s going to happen, especially with the rules written in such a way as to “hide the crime”. And that’s exactly what the rules will allow, as currently written. It’s an oversight that must be addressed by those making the rules. I don’t think they will know to address it until you point it out.

You made a point last week that I had not thought about. Anyone who does that one thing that “covers the crime”, regardless of whether or not they did “the crime”, WILL be accused of it if they start winning.

Yes Bill, this is something you should talk about. Please, do it. You’ll do people a favor, and it’ll even save those writing the rules a ton of headaches when they realize how this one rule can cause so many problems.

Take care,

Greg


________________________



Friend 404tbang:


I'll gladly discuss this issue with the folks at ARA, if they wish.


Greg, after having several days to think about it, I now wish I hadn't mentioned the subject.


What ARA does is their business.


Your friend, BC


__________________________


PS:


Greg, since you know about this issue I know exactly how you feel........and so do I.


But.....................


What ARA does really isn't any of my business.
 
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