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Broughton - use band saw, not cutoff tool?

shortgrass said:
That ^^^^^^, and there are lots of, shall I say, "not machinists" who are chambering barrels. A cut-off tool, a parting tool is not the best tool for a novice. Everything has to be right when you engage that cut-off to the work. Broughton has to cover their rear as they have no control over the methods, knowledge and experience of the person doing the work. If you can read a tape measure, the band saw is probably the best method to cut-off excess material without screwing up.
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There is no reason to be shy about it. Many of us are very willing to admit we are not machinists and are self taught. Of course, that has little bearing on the quality of our chamber jobs, as my not terribly infrequent 1000 yd BR screamer groups would indicate. Or my sub 1/2 MOA hunting rifle barrels hint at. We can talk about the times the wind hands me my hind end in a different thread..... ;)

However, not being a machinist, there is a definite gap in my knowledge. That what I come to this forum and am extremely grateful the the Bros BAT are only a few minutes away and always willing to help me reach the next level. And one of them did complement me on how my threads look......

Now I did look hard for a class to take on how to operate my lathe when I got it 4 years ago, but the only thing I found were courses on CNC machining. So I jumped in and learned much of the basics the hard way. BTW, experience is NOT the best teacher. Someone else's experience is a much better teacher.

Anyway, the choices a non-machinist with SA (situational awareness) makes are probably different that what a machinist makes. I choose to do things in the way that is hard to mess up. It means I go a little slower. I triple check my work, especially when it comes to measuring and dialing in a barrel.

While I am happy to take a .050" cut on a barrel tenon, I do it at the slowest feed rate at 500 RPM with carbide. I make several passes when cutting threads. I don't cut the relief groove with the threading tool, I change to my little pointy carbide insert tool. I test fit everything. When I chamber, I stop a 1/2" short and inspect with a borescope when everything feels good. If it doesn't feel good I inspect more frequently, which means pulling the flush system and cleaning oil out of the barrel. Whenever I have to try something new I grab an old barrel or a piece of barrel and practice first.

So it takes me about 6 hours to chamber a barrel, thread, and time a brake. I am sure I will get faster, but a real machinist probably takes 1/2 to 1/3 that amount of time and gets at least the same level of quality.

Oh yeah, I use a bandsaw to cut barrels to length. I have to take them out of the lathe and turn them around anyway to thread and crown the muzzle. I also work as close as possible to the chuck.
 
I've been using a saw similar to these for several years now. It uses a carbide blade and there is virtually no heat or stress put into the bbl. The heat goes away with the chip. They are fast and easy but blades are fairly expensive and you can't abuse them and expect the blade to hold up.
It's pretty remarkable how it induces no heat to the part.

 
^^^
Those cold saws are sweeet...
Much better than abrasive blades in a shop, none of that abrasive dust flying around onto the sliding surfaces of machine tools.

I've had my cheap HF band saw for prolly 7 years now- I use it a lot more than I thought I would, and it's a decent machine for what they cost.
Flip it to vertical and it's great for general use cutting stock for machining misc tooling and other projects.
 
I remember talking to Tim North about this topic. He told me the parting tool could induce stress up to .250 away from the cut. Now there was a lot more detail he went into and Id guess that would be an extreme worst case. A parting tool would be the heaviest load you do in the chambering process. If your going to ever make a barrel move in its setup, it will be when parting. Drilling the the chamber before boring is the second highest load. Turning and threading are pretty light jobs. Tim is a smart guy and he had a lot of knowledge about barrels and I was very disappointed when he closed up. His heat treat was excellent and he made the best .338 barrel that money could buy, and they would out run every things else by 100 fps. One of my best dashers was a Broughton 5c, 105s at 3150 in 28". His barrels were the fastest that you could get.
 
Alex Wheeler said:
I remember talking to Tim North about this topic. He told me the parting tool could induce stress up to .250 away from the cut. Now there was a lot more detail he went into and Id guess that would be an extreme worst case. A parting tool would be the heaviest load you do in the chambering process. If your going to ever make a barrel move in its setup, it will be when parting. Drilling the the chamber before boring is the second highest load. Turning and threading are pretty light jobs. Tim is a smart guy and he had a lot of knowledge about barrels and I was very disappointed when he closed up. His heat treat was excellent and he made the best .338 barrel that money could buy, and they would out run every things else by 100 fps. One of my best dashers was a Broughton 5c, 105s at 3150 in 28". His barrels were the fastest that you could get.
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I’m glad to hear that. This is a 6mm 5c.
 
I am a machinist, an abrasive wheel, will interduce heat , this in return can cause material to stress relief and no longer be straight. That heat can also draw out carbon , causing heat treated affects......
I personally don't see an issue parting it off, as long as you have coolant on the cut.

Aaron
 
Someone could call Broughton and see what they have to say.
Seems like one of the precision gunsmiths made it a point to say on his home page that he sawed his barrels off and didn't use a cut off tool.

Hal
 
Parting is a big mystery to some. If done properly, it won't introduce any more stress than a turning or threading tool. Reason for the warning, chances are good that the "some" I've referred to could be quite a bit. I've seen many p*ss poor parting attempts, lol. I usually cut on bandsaw myself. Just because it's quick and easy. Cut crown and/or thread muzzle is usually done last
 
^^^^Chuck is spot on^^^^Surface speed, tool geometry, tool setting and workpiece ridgidity are more critical with parting. The last production parting job I witnessed was 3" round cold rolled in a three jaw LeBlond. He drilled a 3/4" hole and then used an carbide insert parting tool to slice off two inch long donuts. Ran the machine as fast as it wold go and used the cross slide feed at .010 per revolution. Chip rolled off in a blue ribbon. Could do four up to the chuck before pulling more bar stock through. As above "some" tried to do it with high speed steel with cutting oil and reverted to the band saw and doing each one individually.
That method wasn't going to make any money hence, the move to carbide.
 
off subject. Been a whole bunch of barrels hacksawed and re-crowned with a T-handle tool...make a "truck gun" you can get out of the window fast...I have even seen a couple that were shooters.
 
hogpatrol said:
^^^^Chuck is spot on^^^^Surface speed, tool geometry, tool setting and workpiece ridgidity are more critical with parting. The last production parting job I witnessed was 3" round cold rolled in a three jaw LeBlond. He drilled a 3/4" hole and then used an carbide insert parting tool to slice off two inch long donuts. Ran the machine as fast as it wold go and used the cross slide feed at .010 per revolution. Chip rolled off in a blue ribbon. Could do four up to the chuck before pulling more bar stock through. As above "some" tried to do it with high speed steel with cutting oil and reverted to the band saw and doing each one individually.
That method wasn't going to make any money hence, the move to carbide.
Click to expand...
I needed a 2"ID, 3.5" OD disc a while ago. Similar shaped part, different method. It's basically a curved parting blade ran in from the face.
Extremely handy tools to have.

 
Walt Krafft said:
I wish that video went to the point where it cut threw. That can get exciting.
Click to expand...
Haha, no.
I stopped .010 short and broke it out! I'm not that brave.

If you listen, I was getting some chatter. The tools only work in a certain diameter range and I was below the min spec so the underhang was rubbing the outside of the groove.

I dropped the RPM and it went smooth for the larger cut.
 
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