What's new
What's new

Need CNC milling machine advice for odd barrel fluting

Dustin_Drews

Plastic
Joined
Oct 10, 2021
My rifle rebarrel/prefit barrel businesses is starting to take off.
This summer I bought a little Haas tl1 that has been a game changer for our shop. I keep getting request to do barrel fluting.
This has started me down the rabbit hole of researching different solutions to flute rifle barrels.

Option one and the option i really want pursue would be a machining center with live tooling.

I already contour my own blanks. So if the the fluting could be done at the same time I contour the blank with live tooling this would be amazing. But I am getting conflicting reports if this can be done. The belt driven spindles do not allow the fancy wrap around flutes some guys are requesting. If anyone has any information they could share on if it could be done I would appreciate it.

The turning center would open up so many other possibilities for me to pursue. It scares me. But at this time it would mainly be used to contour and flute barrels. Cost is a hindrance of this and so is size… Size more so then cost at the moment. They take a up a huge amount of space.

Size is another downside to using a milling center. Once you get a large enough to have enough x travel you’re dealing with a beast of a machine.

So this has me researching cnc knee mill / bed mills with a 4th axis. They should hold more than enough tolerances to do the fluting. They don’t take up a huge amount of space and for the cost. I could afford for it to sit a little bit and not need it to make money every hour of the day.

The research I have done has lead me to believe that Centroid is the way to go. Am I correct on this assumption? I have a brand new Acra knee mill I could convert. Never done it but it looks doable. I would prefer to buy one ready to got to work but that is proving to be harder then it sounds.

What are your guys thoughts? Am I on the right track? I’m I missing anything?

Thanks a bunch.
God Bless,
Dustin
 
How long are the barrels you want to do ? I'd be tempted to think about a barber-colman hobber. They are not quite as versatile as live tooling on a lathe but would do about 90% of what I've seen, and the nice thing is they are set-and-forget. Put the part in, engage the feed, walk away. No electronics. No programming. For something decorative like this, almost anyone can run one. And the cost is less than either a cnc lathe or mill. (Unless you go fruiitcake, in which case yeah you can spend a lot.)
 
You can use a dividing head on a turret mill. One of the advantages of this is that you can tilt the head and get a better cutting condition using a ball nose cutter. Be aware that you can potentially induce stress and ruin a good barrel.
 
Isn’t that shape perfect for integrex? I think a southwest knee mill can do it, budget friendly a cnc masters Supra can, it would take creative programming.
 
Just as an aside I am currently in the process of setting up the manufacturing of actions and we will be offering bolt fluting. I will be using the dividing head and gear train on my turret mill to get started even though I have a 6 axis lathe with live tooling. If you have a huge number to do CNC is the way to go otherwise manual is more than adequate. Keep in mind this is a cosmetic feature not a barrel cam that requires high precision.
 
If you have a huge number to do CNC is the way to go otherwise manual is more than adequate.
It depends on what his idea of "expensive" is. These'd fit a 16-36 or Type A barber easy. Prices on those vary from $500 to $25,000 but if you watch, you can come up with a cheap one. The drawback would be if he wanted to do flutes that were not symmetrical around the part - with a mill you could make the ones on top longer and the ones on bottom shorter, if that was what he wanted. Or change the spacing. Hobbing can't do that. (You can do missing teeth but not close and far).

But with a hobber, you pop the part between centers, lock the tailstock, put the slide where you want, lower the part onto the cutter to depth, then click the button or move the lever. Come back in twenty minutes and it's done. Machine stops on its own. Depending on number of parts, whether the flutes have to end symmetrically, and how cheap he can find a machine, it's an option.

In fact, now that I think of it, there's really old automatic gear cutters that just mill one slot, then index, then mill another until done. Those are definitely cheap and could be suitable for this.
 
It depends on what his idea of "expensive" is. These'd fit a 16-36 or Type A barber easy. Prices on those vary from $500 to $25,000 but if you watch, you can come up with a cheap one. The drawback would be if he wanted to do flutes that were not symmetrical around the part - with a mill you could make the ones on top longer and the ones on bottom shorter, if that was what he wanted. Or change the spacing. Hobbing can't do that. (You can do missing teeth but not close and far).

But with a hobber, you pop the part between centers, lock the tailstock, put the slide where you want, lower the part onto the cutter to depth, then click the button or move the lever. Come back in twenty minutes and it's done. Machine stops on its own. Depending on number of parts, whether the flutes have to end symmetrically, and how cheap he can find a machine, it's an option.

In fact, now that I think of it, there's really old automatic gear cutters that just mill one slot, then index, then mill another until done. Those are definitely cheap and could be suitable for this.
I think space is at a premium. You also don't want to get too funky with these things. Barrels take very little to stop shooting accurately. Accuracy International did extensive testing in controlled environments and decided fluting wasn't worth it. Unless you have a truck axle barrel and can't make weight in the class you shoot in its probably not worth the risk. However the customer is always right and if they want it they get it.
 
I think space is at a premium. You also don't want to get too funky with these things.
Hobbers aren't funky, they'll hold a thou tooth to tooth all the way around the part no problem. Even really old ones are usually good that way.

Space, sure, but then anything that you can put a bar 28" long in will take up space.

I don't expect him to do it because, ya know, The Unkown, but if you had to do this job, I'd certainly look at that way.

Hurth also made some spline millers that would work - they are like a duplex horizontal mill, but for small cutters. One of those would do a nice job but they are not so common and maybe too expensive for him.

For one or two yeah, a 48" bridgeport and a phase ii index head and he's on his way. But for more ....

(Now you know why I never made any money. Machine ? Machine ? An excuse to buy a new machine ? Can we ? hunh, can we dad ?)
 
Hobbers aren't funky,
I meant funky as on the actual fluting on the barrel. Given half a chance customers would ask for V grooves because they look cool. Kaboom at those pressures is not cool.
 
I meant funky as on the actual fluting on the barrel. Given half a chance customers would ask for V grooves because they look cool. Kaboom at those pressures is not cool.
Oh. Yeah, there's nothing to keep a guy from some bad shape with a hob, just like with a mill. Dumbness is pervasive :)

But you can definitely get hobs that will leave a nice radius in the root, and even round over the tops if you want. Gear teeth aren't the only shapes you can hob.
 
But you can definitely get hobs that will leave a nice radius in the root, and even round over the tops if you want. Gear teeth aren't the only shapes you can hob.
But why? A nc knee mill with a dainty fourth is more versatile and easier to set up with whatever flute pattern customer wants. A radius slotter bit or lollipop and all the cutting force is straight into tailstock or fourth- no need for super rigid one. Add in barrel engraving with the same machine.
 
Volume. I agree for just a few a mill is easier but if you were doing very many, the hob is a ton faster and takes almost no attention. I'd say 5 a week, meh but twenty a week, then automated.

Pretty sure he's not going to but threads stay archived here, maybe some day someone will want to produce 100 a month, something to consider.

Hurth spline mill is always going to be worth considering, has two spindles, cuts twice as fast.

Also, this is speculation, but hobbing could help maintain barrel straightness. It's a continuous process, all the way around, moving doewn the long way. If you mill slots, you pull a big gash out of one side, then the other. Metal moves. If you gash one side, then the opposite, and move around in a kind of criss-cross pattern, maybe the thing will stay mostly straight. But hobbing, it's removing metal all the way around all the time.

If nothing else, that's good for blowing smoke, which is what a lot of marketing is based on :D
 
Last edited:
Small batched Hobbed on our production floor or craft milled at our downtown studio?
Hobbed in a bespoke high precision stress free process on our one of a kind special purpose machine in our custom built facility.

Edited to add. Allowing your barrel to show it's true potential.

I'll see your Aerospace grade 6061 and raise you medical grade Titanium with proprietary nano tech coatings :cheers:
 
What ever machine you choose it will have to be capable of providing a very good finish in the flutes along the barrel.

Look at some fluted barrels, and the finish in the flutes is generally very (and should be) good.
 
Hobbers aren't funky, they'll hold a thou tooth to tooth all the way around the part no problem. Even really old ones are usually good that way.

If you put in a 26" long barrel (for arguments sake) that is maybe 1" dia, and you machine flutes 23: long, wouldn't you get deflection and chatter around the mid point of the barrel as the L/d is much higher the your typical gear?
 
the only thing i hate worse than fluted barrels is spiral fluted bolts ...and recessed three lug bolts .....hate them ......and multi coloured plastic stocks ......any plastic stocks for that matter ..........and gross plastic trigger guards and plastic magazines .....hate them too.
Don't hold back John let it all out:cryin:
 
If you put in a 26" long barrel (for arguments sake) that is maybe 1" dia, and you machine flutes 23: long, wouldn't you get deflection and chatter around the mid point of the barrel as the L/d is much higher the your typical gear?
They do make steady rests but in general, the forces from hobbing are axial, not radial. That's one reason you can take a honkin' big cut with a pretty feeble setup. The cutting forces try to push the part onto the table or the chuck, rather than pushing the blank sideways against the arbor.
 








 
Back
Top