First time cutting flutes in a barrel

[Mikado Do]

My first time fluting a barrel.It's a stainless barrel.I would like to know what type of cutter to use,also what material the cutter should be made of.
Thanks for any and all help..........

[pete]

FWIW,
I haven't cut barrel flutes yet, but my 6 mm ppc was done with a blade type radius cutter. I guess a ball mill could also be used. Personally I prefer the look that those blade cutters leave where the tool sweeps out of the groove and the ends of that groove come to a tapered point. A ball milled groove ends far too abruptly for my tastes. Your thoughts may vary. If your mill will go slow enough on the rpms to drive a 3"-4" diameter cutting tool, then you should be able to use just a standard HSS radius cutter. Carbide tipped is pretty expensive in that shape. Properly supporting and clamping the barrel to prevent chatter yet still allowing access for the tool will be your largest problem. And if it were me? I'd experiment with some mild steel rod or a scrap barrel with roughly the same diameter and length before you try it with a good and costly barrel.

Pete

[GeorgeGaskill]

I used a carbide ball nose end mill so it would stay sharp throughout the process. My barrel was cylindrical so it wasn't too hard to set up. As I recall, it was held in an indexer and footstock and I clamped it to an angle plate in the middle for more uniform support.

[steamin10]

OK, Just so I understand, you milled on the sdie of the barrel, and not the top? That way the cutting action is full tool, and not a spot that spins in the center. Do I have that right? Then it is a smple turn to mark and make the next groove.

What is the function of making such grooves in the heavy target abarrel. Is there any performance issue enhanced, or is it just lightening the barrel and pure decoration esthetics.?

[GeorgeGaskill]

No, I clamped from underneath and cut on the top with the spindle vertical. I didn't see any issue with the center of the end mill cutting. I have heard to tilt the spindle so the center isn't cutting but that was after I had done the barrel. That would give a little different exit shape but no matter for me.

I fluted for weight reduction since a fluted barrel is a little stiffer than a round barrel of the same weight. The rifle was way out of balance before fluting; much more recently, I added additional weight to the butt for better balance, and it is better balanced now although it is also 17 pounds. But that is not so much an issue as I am using the rifle only for 600 yard and longer prone.

[HotGuns]

I've fluted lots of barrels, mostly for .50 BMGs and other .50 variants. You'll need a way to spin them to get consistent spacing.
I cut on the top dead center using a carbide ball end mill. To keep stress in the barrel to a minimum, I always cut in stages. I go half depth on one flute, flip it 180 degrees so that any bend in the barrel from relieving itself is eliminated and then repeat the process until its done. On the last cut, I'll only go about .005 deep. This will eliminate any chatter if there is any and get rid of deflection.

Since a picture is worth a thousand words, here's a .50 barrel that I did several years ago.

Here's a pic of the cut.


Picture of the setup


and the barrel before the final polishing...

[AR15DCM]

OK, Just so I understand, you milled on the sdie of the barrel, and not the top? That way the cutting action is full tool, and not a spot that spins in the center. Do I have that right? Then it is a smple turn to mark and make the next groove.

What is the function of making such grooves in the heavy target abarrel. Is there any performance issue enhanced, or is it just lightening the barrel and pure decoration esthetics.?

Fluting a barrel achieves several things.

First it stiffens the barrel. When firing a rifle there is a phenomena called barrel whip. And it is just that the barrel has a whipping action as the bullet leaves the barrel. It creates more surface area for cooling. It reduces weight of the barrel.

[pjs]

I cut on the back side with a shanked cutter in the vertical mill. I back up the front side with an angle plate with two brass tipped screws threaded into it. The screws make it easy to maintain the pressure on the barrel. I find that "climb" milling gives the best finish. The barrel is held each end in 5c collet spin indexers. HSS tooling works fine and is much cheaper than carbide. Usually I use an 1/8 radius (1/4 diameter) cutter for most flutes.
Pete

[AR15DCM]

How many flutes are you cutting with a 1.8" cutter?

I bought a 1/4" cutter and was wondering if that was going to be too wide.

[pjs]

I usually cut 6 flutes. You could cut 8 on a really heavy barrel but to me it looks to "busy" on a small barrel especially near the muzzle end. I like to see the lands as wide as or wider than the flutes for a good look. On smaller barrels I often use a 3/32 radius cutter (3/16 diameter).
Pete

[pjs]

"I bought a 1/4" cutter and was wondering if that was going to be too wide."

Keep in mind that you do not have to go full depth and therefore the flutes won't be 1/4" wide. If the job is just for looks then you only need a light cut. A depth of only .040 will give you a groove of about .180 with your 1/4" diameter cutter. It is 1/4" diameter not radius? They are usually listed in the tool catalogs by radius.
So in this case; 6x.180"=1.08" of barrel circumference would be flutes. So that would be 50/50 flute/land on a barrel with a 2.16" circumference or .687" diameter. (2.16 divided by pi). So your 1/4" diameter cutter should be fine on most barrels.
Pete

[AR15DCM]

"I bought a 1/4" cutter and was wondering if that was going to be too wide."

Keep in mind that you do not have to go full depth and therefore the flutes won't be 1/4" wide. If the job is just for looks then you only need a light cut. A depth of only .040 will give you a groove of about .180 with your 1/4" diameter cutter. It is 1/4" diameter not radius? They are usually listed in the tool catalogs by radius.
So in this case; 6x.180"=1.08" of barrel circumference would be flutes. So that would be 50/50 flute/land on a barrel with a 2.16" circumference or .687" diameter. (2.16 divided by pi). So your 1/4" diameter cutter should be fine on most barrels.
Pete

This is what I ordered: http://www.grizzly.com/products/H3343

The barrel is 28" and is .90" at the muzzle. I really want to cut it down to 26" or 24" before I flute it. The main reason for fluting is to reduce weight and stiffen the barrel.