notebook: button rifling
Retrieved: 12/05/2013
TRX
November 19, 2013
I'll be adding to this topic from time to time. I have a project for which
I'd really like a .311" barrel with a 1:7 twist, basically a Kalashnikov-style
.300 Whisper. It would be much more sensible to just fake it with a .308
barrel, but you know how it is...
First, I think it should be practical to make a button out of O-1 or HSS steel. From O-1, the basic shape could be cut on a lathe. The helical grooves for the rifling would need some sort of guide fixture and a thin grinding wheel. There's a thread on weaponeer where someone cut a button by hand with a Dremel, a lot more ghetto than I would expect, but apparently it worked.
Second, I've seen some discussion about whether the button has to be twisted as it goes down the bore, like a cut rifling head. I've seen a couple of people who claimed to have owned or run button machines claiming their machines twisted the button... but after considering this for a while, I'm inclined to think that even if they do have a helix for that, it's not going anything. You're talking about a pullrod of 1/4 to 5/16 diameter, two to three feet long. That's a nice springy torsion bar. I figure the button would lag behind a bit as it entered the bore, a few degrees of twist on the pullrod against the helix, and then after that the button is self-guiding due to its grooves; I think the twist on the pullrod would be constant until the button pops out.
There are some builds out there with machines with no helix, guided only by the button, that seem to have worked just fine.
raven007
November 19, 2013
I have wondered if you could build a piloted button and use a grease gun to
build enough presuure to forced the button along the barrel. I think the
button would rotate of its own accord.
shred
November 19, 2013
Quote
Doesn't the button have the twist 'built-in' with the angles on it? Then you
need a twisty thing on the pull-rod just so it stays with the program and
doesn't turn into a candy-cane, but I would sort of doubt it's actually
pulling the button around.
You'd probably have to run the O1 almost full-hard, but it should be doable. I think the commercial guys use carbide, but they do a lot more.
This is some interesting reading too: Button Rifling patent: https://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US2383356.pdf
Interestingly it's a push setup, although pull seems preferred by most these days.
turbojet
November 19, 2013
I did alot of research on rifling and from what have seen they all basically
have a gear rack to "drive" the button in a spiral and a hydraulic ram to
force it through I have seen both push and pull types. But there is also
another type too I'll post the link at the bottom of the post. It's pretty
neat and some what simple to build. My choice though would be hydraulics
strong and simple as well.
check this out http://www.network54.com/Forum/550526/thread/1211906717/Rifling+Machine
barnbwt
November 19, 2013
"I have wondered if you could build a piloted button and use a grease gun to
build enough presuure to forced the button along the barrel."
Or just kick the button through with a blank cartridge! :D :o (as stupid as it sounds, I have to wonder if it could work... ???)
"You're talking about a pullrod of 1/4 to 5/16 diameter, two to three feet long. That's a nice springy torsion bar."
I imagine it really depends on how much force is needed to cause the button to spin as it is pulled. The action cross section of the button swaging the barrel is pretty narrow, so I imagine it's less force than I'd think. For something like a BP gun with a super-slow twist, it seems like it would be difficult for the button angle to be made shallow/accurate enough to deliver a consistent 1:20" or whatever twist rate. For a 1:6" .22 barrel, yeah, I seen no way forward other than a helical button that "taps" its own path down the
bore. An angle-sensing stepper motor that has a torque-sensor feedback could easily force the button along a set path, however, including fancy progressive rifling ;D. Wouldn't surprise me if that's what the pros use, simply because the twist wouldn't be dependent upon tool condition so much.
turbojet
November 19, 2013
??? ??? Interesting thoughts but most of what I have seen has a gear rack
with interchanging gear sets that control the rifling twist rate button
rifling.
Check this link out http://firearmshistory.blogspot.com/2010/05/rifling-manufacturing-button-rifling.html
Got some decent pics and some verbiage about button rifling.
turbojet
November 19, 2013
Here is another site with alot of info.
http://riflingmachinemethods.com/?page_id=2
Better pic of a hydraulic with gear rack
shred
November 19, 2013
In the patent, they make the button by swaging it through a section of cut-
rifled barrel to get the twist rate & shape they want. The inventor there is
the father of the Remington 700 as well as a lot of their other rifles.
TRX
November 19, 2013
Quote from: raven007
I have wondered if you could build a piloted button and use a grease gun to
build enough presuure to forced the button along the barrel. I think the
button would rotate of its own accord.
You know... that would be so cheap and simple to try, it would be crazy to build a fancy machine without giving it a shot.
Grease guns can make a lot of pressure; there are people who use them for hydroforming two stroke expansion chambers too.
> button
I'm pretty sure the commercial barrelmakers use carbide because it's cheaper in the long run, since it wouldn't wear like a steel button. For one or two barrels, I'd be willing to give a steel button a try.
I have some "Thredfloer" taps, which swage threads into holes without cutting. They're plain old HSS as far as I can tell, and they're swaging .010 to .020" deep threads instead of mere .003" or so rifling...
> LaBounty book
That's the only one I know of that I don't have yet.
I keep looking at the cut rifling stuff. Making the machine looks straightforward, but the cutter head looks like a hassle. Interestingly, I've found a number of cut-rifling machines for sale over the years, but none of them had the cutter heads...
barnbwt
November 19, 2013
Quote
In the patent, they make the button by swaging it through a section of cut-
rifled barrel to get the twist rate & shape they want
Ooh, neat! Yet another miracle of heat-treating; swage the annealed slug through a template "cut" rifled barrel (since buttons don't exist yet ;) ), harden the crud out of it, maybe sharpen it, and ram it through a softer normalized barrel :P
jim r
November 20, 2013
The Marlin Micro Groove barrel may be the one to try that with. No sharp
edges. :P
gunnie7
November 20, 2013
I don't know if high speed steel could be annealed soft enough to be
effectively swaged, just personal opplinion from experience trying to forge
the stuff. That being said if you could make a die in the form of a cut rifled
barrel you might be able to somehow force it through the die at an extremely
high heat but anneald and cold I personally doubt it
barnbwt
November 20, 2013
The forming barrel would be hardened before the swaging, too
TRX
November 20, 2013
There are two different methods of buttoning - one pass and two pass. The
two pass shoves the swaging button through, and then a second pass with
another button that's supposed to remove any "fins" left by the first button.
The single-pass method puts two swollen areas in the same button, to save
time.
Of course, still other sources say the button is oversize, and the barrel springs back behind it as the button is forced through, so there'd be no "fins" in the first place.
Unlike cut rifling, buttoning doesn't seem quite as cut and dried...
I think you'd have to make more than one button, to see how "springback"
worked, and maybe try more than one bore diameter. Or cheat and call DME and
see if they'll tell you.
I originally was sketching some elaborate fixturing and a grinder head to
grind the button to shape and cut the helical grooves. Then I realized you
could do the barrel shape with files on the lathe; I don't think there's any
particular shape required, just the diameter.
Likewise, I don't think a perfect helix would be needed. The intersection of the grinding wheel and the barrel shape of the button would only be, what, an eighth of an inch or so. So I think you could cheat by just running the grinding wheel across at an angle. There error between a true helix and a straight line should be miniscule. And, hey, if not, it's an experiment...
barnbwt
November 20, 2013
You mean, "hobbing" like (IIRC) Enfield did to cut square threads with a
rotary tool? I remember seeing a chart for error between true helixes and
this approximation, and it's pretty low, unless you need absolutely
perpendicular-to-axis walls in your cuts.
raven007
November 20, 2013
And the thing about it all is a barrel doesn,t need to be beautifully
accurate, only beautifully consistent. who cares if you create rifling which
is off center or not perfectly the same twist throughout the length and the
end result is a barrel which puts rounds an inch high and to the right two
inches, as long as it always puts rounds an inch high and to the right two
inches. ;D
TRX
November 21, 2013
> hobbing
Exactly! And if you find at chart again, please post it or a link to it
somewhere...
barnbwt
November 21, 2013
http://www.mhi.co.jp/en/products/detail/ind_hob.html
It's all in here, I think, though it's also all Greek to me :D
I'm not entirely sure cutting slots in the sides of the button with a grinding wheel or saw is geometrically equivalent to a spiral-hob's tool path through a spur gear, my guess is the quasi-helical path taken by both have a similar error figure which is mostly dependent upon the cutter radius and radial depth into the workpiece. I'm also fairly confident the error is on the order of single-digit degrees, which equates to ~0" for the depths we're interested in ;)