Spiral fluting?

[halfmoonclip]

There was a study, someplace, that found the only thing that helped a barrel tolerate heat was more metal.
But spiral fluting looks incredibly cool.
Moon

 

[MachIVshooter]

You can do it with a rotary table or a dividing head and a vertical mill large enough to handle them.

Yes, knee mill is a vertical mill reference, but is more specific to your typical full size Bridgeport type with an articulated head, not inclusive of benchtop machines that would be too small or monstrous Cincinnati or K&T things with fixed orientation spindles that turn slowly and are meant to make thumbnail sized chips cutting workpieces weighing hundreds or thousands of pounds.

A rotary table with the ability to stand vertical certainly could be made to work. Dividing heads are simply the tool which is designed for machining round things on mills with tail stocks and typically collets, chucks or dead centers with dogs for workholding. To do it on a rotary table, you'd need to sort out your workholding and then come up with a tailstock to do barrel work, and may have to get more creative for quill/head clearance due to the generally larger dimensions of the rotary table.

 

[lysanderxiii]

Yes, knee mill is a vertical mill reference, but is more specific to your typical full size Bridgeport type with an articulated head, not inclusive of benchtop machines that would be too small or monstrous Cincinnati or K&T things with fixed orientation spindles that turn slowly and are meant to make thumbnail sized chips cutting workpieces weighing hundreds or thousands of pounds.

A rotary table with the ability to stand vertical certainly could be made to work. Dividing heads are simply the tool which is designed for machining round things on mills with tail stocks and typically collets, chucks or dead centers with dogs for workholding. To do it on a rotary table, you'd need to sort out your workholding and then come up with a tailstock to do barrel work, and may have to get more creative for quill/head clearance due to the generally larger dimensions of the rotary table.

Work holding - you put a chuck on your dividing head/rotary table, and most dividing heads come with a height adjustable tailstock, so that's no big problem

Like I said, you can do it with a dividing head, if you have the patience . . . advance a few thousandths, then rotate a half a degree, repeat as necessary. This way you only have to do one flute, once you have a master spiral, you can cut barrels the same way rifling is cut, just on the outside.

And no, you probably aren't going to do it in a Grizzly.

 

[lysanderxiii]

There was a study, someplace, that found the only thing that helped a barrel tolerate heat was more metal.
But spiral fluting looks incredibly cool.

Moon

If the only object of the game is to keep the barrel temperature low. There are two ways to do this:

1) Make a barrel that can reject heat quickly (fins, flutes, water jackets), or

2) Make a barrel that takes a lot of heat to make the temperature rise (large amounts of mass).

Imagine a rifle barrel is bucket with a small hole in the bottom under a running faucet of water. The height of the water in the bucket is analogous to the temperature of the barrel. The volume of the bucket is analogous to the amount of heat the barrel can withstand before it is weakened to the point of failure. The hole in the bottom is analogous to the heat dissipation properties of the barrel. The flow of water is analogous to how fast heat is introduced to the barrel.

If you have a big enough hole in the bottom of the bucket (good heat rejection), and a low water flow (slow heat injection, i.e., low rate of fire), then you do not need a big bucket (heavy barrel) to handle the heat. If you have the faucet full open, you are going to want a big bucket no matter how big the hole in the bottom is.

 

[MachIVshooter]

Like I said, you can do it with a dividing head, if you have the patience . . . advance a few thousandths, then rotate a half a degree, repeat as necessary. This way you only have to do one flute, once you have a master spiral, you can cut barrels the same way rifling is cut, just on the outside.

Oh, heck no. Lol. Way too painstaking, and the constant starts and stops would make one ugly flute. Plus you'd have to come up with a tracing system that works on a tapered helix, and a rigid yet free spinning enough set up that would allow the tracer to move smoothly without inducing chatter. That's a tall order.

The right way is to take the handle and plate off, install a gear or cogged pulley, do the same with x-axis lead screw, then figure out your ratio and drive train to rotate the dividing head (or rotary) at the same time x is traversing for accurate, repeatable and smooth cuts.

Most lead screws on full size knee mills here are .200" travel per revolution, and most dividing heads or rotary tables are 90:1, so if you wanted a full revolution helix over 18", you'd actually be able to drive directly 1:1

 

[lysanderxiii]

Oh, heck no. Lol. Way too painstaking, and the constant starts and stops would make one ugly flute. Plus you'd have to come up with a tracing system that works on a tapered helix, and a rigid yet free spinning enough set up that would allow the tracer to move smoothly without inducing chatter. That's a tall order.

The right way is to take the handle and plate off, install a gear or cogged pulley, do the same with x-axis lead screw, then figure out your ratio and drive train to rotate the dividing head (or rotary) at the same time x is traversing for accurate, repeatable and smooth cuts.

Most lead screws on full size knee mills here are .200" travel per revolution, and most dividing heads or rotary tables are 90:1, so if you wanted a full revolution helix over 18", you'd actually be able to drive directly 1:1

Ugly? Not really, the cam for this bolt carrier was cut by advancing at 1/2 degree intervals. and it turned out nice and smooth:


Granted, it only moves through 45 degrees, but it was done in a single pass. I get some pictures of the path itself a little later.

And Actually using a tracing pattern was the normal way to make complicated shapes before the advent of computer controlled machines, so, it is not that tall an order.

These days the "right way" to do it would be replace all the handles on the mill and rotary head with motors and hook them up to a computer controller. Cheaper and less involved.

 

[jmorris]

When shooters are regularly firing weapons with barrels of this diameter,..

When I have seen things similar to that, the barrel inside the tube is actually in tension, not really that big. That would be a huge blank though, bigger than my Lothar Walther 50bmg blank was.

Removing metal reduces total heat absorbing capacity, it makes for more surface area but it doesn’t turn a steel tube into a radiator or they would have just fluted machinegun barrels vs water cool them and make them quick change. You could start with a larger diameter barrel and cut flutes until it weighs the same as a smaller diameter barrel and see benefit.

Of course all of the machine work needs to be quite precise (spacing and depth) or you can induce heat effected change in the barrel.

This is worth reading.
https://riflebarrels.com/a-look-at-the-rigidity-of-benchrest-barrels/

 

[WisBorn]

My favorite rifle has straight fluting. I think the spiral flutes are cool looking

 

[Legionnaire]

You guys who can actually cut flutes make me jealous.