Cutting barrel breech angle

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RBaker

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Hey Folks
I am working on practice barrels for a Bat B action. The breech cone/barrel angle is 25*. None of my tools/holders allow me to reach in far enough to cut the angle before the heal of the tool holder rubs on the the barrel. I have ground a couple of HHS tool bits with out much success. They cut, but not smoothly or leave a smooth surface. I have tried different spindle speeds. Anyone offer some ideas/pics on the correct or best geometry for a hhs tool to cut this angle?
Thanks
Bob
 
You just need to grind a tool to fit, starting with the stickout you need to make the cut. Smaller diameter and longer-reaching tools are not as rigid, so you'll be taking finer cuts to get there. For your finish, honing your HSS tools to a mirror sharpness will help. It's really about just placing the cutting edge where it needs to be first, and adjusting your technique to achieve an acceptable finish. That's opposite what you would do when you have lots of room to work, but sometimes it's how the job gets done. Or so says me, whatever that's worth.
 
I'd be tempted to try a 118 deg point drill bit as a boring bar. As large a drill as possible and feed with the compound set at 25 deg. A nice new HSS Co stub drill bit would be ideal.
 
RBaker said:
Hey Folks
I am working on practice barrels for a Bat B action. The breech cone/barrel angle is 25*. None of my tools/holders allow me to reach in far enough to cut the angle before the heal of the tool holder rubs on the the barrel. I have ground a couple of HHS tool bits with out much success. They cut, but not smoothly or leave a smooth surface. I have tried different spindle speeds. Anyone offer some ideas/pics on the correct or best geometry for a hhs tool to cut this angle?
Thanks
Bob
Click to expand...

Bob, I am not a gun guy and have no idea of what the job entails. If the hole is shallow then a boring bar will work but if it is deep then a boring bar will NOT work. It seems to me that an angle like I envision you needing would need to be centered on the bore so a piloted reamer of some kind would be a better option. Again, I'm speaking from ignorance but perhaps a bit more detail or a pic or drawing would help clarify the operation and cut you need.
 
mikey said:
Bob, I am not a gun guy and have no idea of what the job entails. If the hole is shallow then a boring bar will work but if it is deep then a boring bar will NOT work. It seems to me that an angle like I envision you needing would need to be centered on the bore so a piloted reamer of some kind would be a better option. Again, I'm speaking from ignorance but perhaps a bit more detail or a pic or drawing would help clarify the operation and cut you need.
Click to expand...
Guys thanks. A boring bar kinda works, but as Mike says the angle/to hole size is problematic. The bore/hole is 6mm or .243 and the barrel is 1.25", so a pretty deep cut when trying to obtain 25* from the bore outward. It has been suggested to me that a HHS tool ground to a greater than 3/8 radius, with a long reach would work. But I have no pics of this tool and am rank amateur when grinding tools. I guess its dive in and screw up time. Steep learning curve. Hence I am just practicing on old worn out barrels
 
I use one of a few different Micro 100 solid carbide bars, as well as an HSS tool I ground myself. I cut the cone after chambering, so I’m dealing with a hole significantly larger than bore diameter. Both JGS and Manson make piloted cone-cutters. I’ve never used one, and don’t remember if they make a 130°, or not.
A Micro-100 BB-180500 will cut any breech configuration I’ve seen, before or after chambering, on any bore larger than .17 caliber. They’re a little over $30.
 
RBaker said:
so a pretty deep cut when trying to obtain 25* from the bore outward
Click to expand...
I don't understand. Are we talking about a coned barrel tenon that the bolt nose fits into?
Something like this
1608228066393.png
 
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dpb said:
I use one of a few different Micro 100 solid carbide bars, as well as an HSS tool I ground myself. I cut the cone after chambering, so I’m dealing with a hole significantly larger than bore diameter. Both JGS and Manson make piloted cone-cutters. I’ve never used one, and don’t remember if they make a 130°, or not.
A Micro-100 BB-180500 will cut any breech configuration I’ve seen, before or after chambering, on any bore larger than .17 caliber. They’re a little over $30.
Click to expand...
Thanks dpd. I will check out the micro boring bar
 
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