That Made in Canada M203 project...
- Thread starter sigger69
- Start date
To explain my comments in the above post a little more clearly:
A rifling button that size alone would be an expensive item, as would the equipment required to use it. Prohibitively so for 100-200 tubes.
I suppose if the tubes are aluminum, the button could be made of hardened steel to cut down on that expense, and a common hydraulic press with an oil pump could be rigged up to do the job, but that's going to cost a lot of money to get your prototype.
Particularly if you already have access to a CNC mill.
Does this give you any ideas:
You don't even have to buy one. You can turn your own extension and offset bushings to cut a helix up the inside of the tubes on a CNC mill for a couple of bucks worth of material.
A rifling button that size alone would be an expensive item, as would the equipment required to use it. Prohibitively so for 100-200 tubes.
I suppose if the tubes are aluminum, the button could be made of hardened steel to cut down on that expense, and a common hydraulic press with an oil pump could be rigged up to do the job, but that's going to cost a lot of money to get your prototype.
Particularly if you already have access to a CNC mill.
Does this give you any ideas:
You don't even have to buy one. You can turn your own extension and offset bushings to cut a helix up the inside of the tubes on a CNC mill for a couple of bucks worth of material.
Yes, I shouldn't have snapped like that, and I do apologize. Been in a bad mood lately, and I misread what Mike's post actually said.
Look at it this way:
The "buttons" for button rifling have been described to me as normally being made out of tungsten carbide, and a 40mm diameter chunk of carbide is, just by itself, going to be expensive. Then it will actually have to be ground - it can't be cut by conventional tools. So you would have to find some one with a tool grinder large enough to handle that piece, and the skills to do a good job of it. Again, that is going to cost you. As I said above, if you can get away with making your button out of hardened steel, you are going to save a lot of money, but it will still be a lot of work.
Then there is the machine that is going to pull the button through the barrel blank. Industrially these are special purpose machines and are expensive. Remember, you are basically pulling a die through undersize material with great force. Oil is pumped into the bore under high pressure to lubricate this action. I believe that some where around here I have a description of how to actually build one or adapt a lathe to such a purpose, but it is neither cheap nor easy. As I alluded to above, I suspect that a double H frame press powered by a pair of heavy duty hydraulic jacks could be devised to draw the die through the tube, at relatively little cost. Again though, it's a good bit of work and I am not certain that it would work right. Owing to the larger surface area in a 40mm tube than those that are traditionally button rifled (less than 15mm) I suspect that a very great amount of force would be neccesary.
So, setting up to button rifle 40mm tubes only seems cost effective to me if a very large number of tubes are going to be produced, or a small number of tubes at very great cost. And certainly not neccesary if you have access to a lathe and a CNC mill.
What you are doing when you are cutting the rifling in the tube is cutting a long helix on the inside of the tube, which is a relatively simple operation when you have set up correctly. There are extended arbors commerially available, but if you have access to a lathe and are confident of your ability to turn parts accurately you will not need to buy one. What you want to build is this:
Sorry if the image quality is not the best, but it was a quick sketch. This consists of a tool extension (2) that is fitted into the toolholder (1) in an appropriate size collet. The tool (4) in this case is a Woodruff cutter that is soft soldered into a recess in the second part of the tool extension (3). This part (3) is also turned with a shaft that an offset bushing (5) can rotate around, and is threaded to mate with the first part of the extension (2). The offset bushing (5) is the nominal bore diameter less a tolerance and has a bronze bearing (6) to facilitate smooth rotation. The critical dimension for the bushing is (7) which is the amount that the Woodruff cutter protudes beyond the bushing at 0 degrees (or as seen here 180). This is the depth of cut. A seperate bushing will be needed for each pass, as the depth of cut increases. It may be desirable to construct the bushings and select the cutter in such a way that a rod can be passed through the center of the bushing for additional stability. It may be that at a low enough spindle speed with a rigid enough extension, low enough feed, and shallow depth of cut that a bushing may not be neccesary. But that would require a very high degree of concentricity on the extension and I am fairly certain that there would be too much chatter to obtain the desired surface finish.
At any rate. The tube is secured in an appropriate fixture - perhaps a jig - so that the tool at the beginning of it's pass can start below the bottom lip of the tube, but not so far below that the bushing falls below - you want the bushing to stay within the tube the whole time that it is cutting. Lots of lubricant will be required to ensure that the bushing and the extension running through it is rotating freely.
The grooves of the rifling will be hemisperical and not square edged, but should still be functional, and polygonal rifling could be produced in this fashion as well.
And much faster and easier than button rifling by a common machine shop.
For this consultation I require $20 per tube cut this way.
Look at it this way:
The "buttons" for button rifling have been described to me as normally being made out of tungsten carbide, and a 40mm diameter chunk of carbide is, just by itself, going to be expensive. Then it will actually have to be ground - it can't be cut by conventional tools. So you would have to find some one with a tool grinder large enough to handle that piece, and the skills to do a good job of it. Again, that is going to cost you. As I said above, if you can get away with making your button out of hardened steel, you are going to save a lot of money, but it will still be a lot of work.
Then there is the machine that is going to pull the button through the barrel blank. Industrially these are special purpose machines and are expensive. Remember, you are basically pulling a die through undersize material with great force. Oil is pumped into the bore under high pressure to lubricate this action. I believe that some where around here I have a description of how to actually build one or adapt a lathe to such a purpose, but it is neither cheap nor easy. As I alluded to above, I suspect that a double H frame press powered by a pair of heavy duty hydraulic jacks could be devised to draw the die through the tube, at relatively little cost. Again though, it's a good bit of work and I am not certain that it would work right. Owing to the larger surface area in a 40mm tube than those that are traditionally button rifled (less than 15mm) I suspect that a very great amount of force would be neccesary.
So, setting up to button rifle 40mm tubes only seems cost effective to me if a very large number of tubes are going to be produced, or a small number of tubes at very great cost. And certainly not neccesary if you have access to a lathe and a CNC mill.
What you are doing when you are cutting the rifling in the tube is cutting a long helix on the inside of the tube, which is a relatively simple operation when you have set up correctly. There are extended arbors commerially available, but if you have access to a lathe and are confident of your ability to turn parts accurately you will not need to buy one. What you want to build is this:
Sorry if the image quality is not the best, but it was a quick sketch. This consists of a tool extension (2) that is fitted into the toolholder (1) in an appropriate size collet. The tool (4) in this case is a Woodruff cutter that is soft soldered into a recess in the second part of the tool extension (3). This part (3) is also turned with a shaft that an offset bushing (5) can rotate around, and is threaded to mate with the first part of the extension (2). The offset bushing (5) is the nominal bore diameter less a tolerance and has a bronze bearing (6) to facilitate smooth rotation. The critical dimension for the bushing is (7) which is the amount that the Woodruff cutter protudes beyond the bushing at 0 degrees (or as seen here 180). This is the depth of cut. A seperate bushing will be needed for each pass, as the depth of cut increases. It may be desirable to construct the bushings and select the cutter in such a way that a rod can be passed through the center of the bushing for additional stability. It may be that at a low enough spindle speed with a rigid enough extension, low enough feed, and shallow depth of cut that a bushing may not be neccesary. But that would require a very high degree of concentricity on the extension and I am fairly certain that there would be too much chatter to obtain the desired surface finish.
At any rate. The tube is secured in an appropriate fixture - perhaps a jig - so that the tool at the beginning of it's pass can start below the bottom lip of the tube, but not so far below that the bushing falls below - you want the bushing to stay within the tube the whole time that it is cutting. Lots of lubricant will be required to ensure that the bushing and the extension running through it is rotating freely.
The grooves of the rifling will be hemisperical and not square edged, but should still be functional, and polygonal rifling could be produced in this fashion as well.
And much faster and easier than button rifling by a common machine shop.
For this consultation I require $20 per tube cut this way.
MikeH
My intention was to use the CNC lathe more like a shaper then a lathe. Because of the extreme difference between travel and rotation the cutter is going to plow more then cut so why try to fight it. Machines that will do 800-1200 IPM are not uncommon with a RPM of say 20 the twist rate or something close could be made. I realize these feeds a really only intended for rapped location I think it may work with small cuts say 0.001" and soft metal like Al.
If surface finish is not perfect barrels could be cleaned up with a hardened steel button a couple of thrust bearings and a standard 10t shop press as you would only be moving 0.0005 - 0.001" of material
My intention was to use the CNC lathe more like a shaper then a lathe. Because of the extreme difference between travel and rotation the cutter is going to plow more then cut so why try to fight it. Machines that will do 800-1200 IPM are not uncommon with a RPM of say 20 the twist rate or something close could be made. I realize these feeds a really only intended for rapped location I think it may work with small cuts say 0.001" and soft metal like Al.
If surface finish is not perfect barrels could be cleaned up with a hardened steel button a couple of thrust bearings and a standard 10t shop press as you would only be moving 0.0005 - 0.001" of material
peckerwood
CGN Ultra frequent flyer
- Location
- PalePony, Yukon
Found this on a barrel search on a paintball website. Homemade rifling tool.
The cutting bit is held in place loosely by an indexing pin through the front and is pressed upwards by spring pressure. Would prolly work well for Aluminum...hmmm
Peckerwood
The cutting bit is held in place loosely by an indexing pin through the front and is pressed upwards by spring pressure. Would prolly work well for Aluminum...hmmm
Peckerwood
the button rifling that I was refering to...
Since we are using AL, good old hardened tool steel, say D2 would make a perfect blank.
Make 3 - so only a couple thou is removed at a time.
pull them thru - no biggy
We have a 450 Ton press at work - and it has the 350 ton availble retracting.
if that would not do it - I am not sure what will.
I do understand the concept of thread milling, it is just that me, and 2 other CNC programmers have not come up with an effective way of milling good rifling in the manner.
Since we are using AL, good old hardened tool steel, say D2 would make a perfect blank.
Make 3 - so only a couple thou is removed at a time.
pull them thru - no biggy
We have a 450 Ton press at work - and it has the 350 ton availble retracting.
if that would not do it - I am not sure what will.
I do understand the concept of thread milling, it is just that me, and 2 other CNC programmers have not come up with an effective way of milling good rifling in the manner.
MikeH said:
I must be missing something then. Are you saying that you could not come up with an effective way of milling good rifling from a programming standpoint, or as a part of the physical process? Or is it just that the rounded grooves would not be acceptable?
As far as the physical process is concerned, I've described a simple arbor and bushing arrangement that might be effective above. A special jig or fixture might be neccessary and of course your setup would have to be bang on, but it could be done. Chatter would be an issue, but slow enough feed rate could compensate for that.
The programming is by far the easiest step. At it's simplest, the toolpath is just a helix with the correct rate of twist offset from the bore by the depth of cut. In the image below, 8 single pass grooves are depicted. The blue helixes describe the center path of the tool to cut 8 single pass grooves as seen in the pick below that (scale exaggerated):
Or you could machine the grooves in any configuration that you like. Three grooves:
Of course, if you have access to a press of the size that you are talking about, then button rifling is actually going to be easier.
Good luck
SPI
the programming is not a large challenge, we have mastercam. It is how to get the surface finished needed.
Wanna pic of my press? :twisted:
http://engineered.brandt.ca/images/63_big.jpg
It is the big blue thing near the back of the pic on the right hand side Sorry it is not that clear, but you get the point.
18" bore cylinder 4000 PSI
You do the math.
Works out to 462.... ton
the programming is not a large challenge, we have mastercam. It is how to get the surface finished needed.
Wanna pic of my press? :twisted:
http://engineered.brandt.ca/images/63_big.jpg
It is the big blue thing near the back of the pic on the right hand side Sorry it is not that clear, but you get the point.
18" bore cylinder 4000 PSI
You do the math.
Works out to 462.... ton
Hey Mike,
With a press like that it shouldn't be too hard to rig up a button rifling frame.
You probably know all this already, but I will tell you what I know about it just in case:
Button rifling is a process where the metal is swaged and none is actually removed, so there is no advantage to "working in" to the desired depth of groove with successive sizes of dies. In fact, the work hardening that is the result of each pass of the die could be detrimental to the piece - possibly producing spalling or cracking in extreme cases. In any event, it seems to be at most a two stage proccess.
If an adequately bored and reamed tube is available, it is only a one piece operation. If not, a button is made to the correct diameter for swaging the lands, and passed through the barrel drilling to "button ream" it. It is then rifled with the "rifle button":
Excuse the coarse drawing and note that it is not to scale. The tapered ends are a few thou smaller than the bore size. The waist of the button (1) is .0015"-.002" oversize of the desired depth of groove to allow for springback in steel barrels. I am not sure that this would be neccessary in most aluminum alloys. The button's grooves (3) are of course, cut significantly undersized from the lands of the barrel to avoid marring them. The button is sweated to a piece of drill rod that serves as a pull rod by means of a post (2) inserted into the rod. I suspect that this is done so that if the pull rod snaps during the proccess it can easily be removed and replaced, whereas a mechanical connection like threading that runs contrary to the grooves could prove to be very difficult to seperate after the first time the button has been used. Even so, you will have to do something like that if you are using a hardened steel die, as hard soldering would draw the temper back to being uselessly soft. Threading is probably acceptable in your application, as I just can't see a 20-30mm diameter length steel rod failing before the aluminum tube. The reaming button is of the same configuration without the grooves.
Other pictures of buttons that I have seen have pilots, and some even have bushings fore and aft of the die, but I do not think that they are neccessary. If lubrication is an issue you could have keyways that correspond to the grooves cut into an undersized pull rod that has a section of tubing slid over it so that oil can be pumped into them, but again, I do not think that is neccessary.
Here is a simple rig, based on a vertical button rifling machine that was described to me:
It's simply a rectangular frame made of square steel tubing. A piece of tube or pipe (3lower) with a bore slightly larger than the diameter of the barrel blank (1) is slid onto the blank. The blank is then slipped in to a similar piece of tubing (3upper) that is welded to the frame, and the blank pulls against a thrust bearing (4). (3lower) then drops into a mating piece of pipe (2) that is welded to the bottom of the frame to steady the barrel blank (1). The pull rod and attached button are then drawn up through a hole in the top of the frame (5) having been earlier inserted through a corresponding hole in the bottom of the frame (not illustrated) and barrel to attach to the press head.
You will note that in the above description, it is the barrel that rotates as the button passes through it, not the other way around, and that the barrel bears against the thrust bearing at the top of the frame. This arrangement has apperantly been used for rifle barrel blanks which have very thick wall thickness in comparison to bore size, and I have some concern that the thinner wall to bore ratio expected in a 40mm tube could lead to buckling problems.
This can be overcome in several ways. The first of course, is ensuring that there is adequate lubrication to overcome any friction issues. The second is to start with a much thicker barrel blank, and the third is to anchor the bottom of the barrel while the button is being pulled through it:
This frame - made out of a heavy I or U-beam with end caps welded on - is a more elegant solution anyway, and probably the one that I would build. In this case, the barrel blank (1) has been turned down so that it has a thick (0.5-1xbore dia) flange (4) that rests in a thrust bearing (3) on the bottom end cap (2) with the pull rod being drawn out the top hole (5).
A few other things of note:
From what I have learned, lubrication and the elimination of unneccesary friction are critical both in terms of surface finish, and to avoid any tool/material failures.
It's important to remember that you are not cutting the metal, you are deforming it, and that means that the application of force in any direction may affect the finished piece. So in the case of the frame first illustrated buckling and bulging are an issue. In the case of the second frame, stretching, elongation would be issue. It may be neccesary to add additional bearings, bushings, and supports, or otherwise fine tune the proccess.
Once perfected though, you should be able to pop out a barrel every few minutes.
With a press like that it shouldn't be too hard to rig up a button rifling frame.
You probably know all this already, but I will tell you what I know about it just in case:
Button rifling is a process where the metal is swaged and none is actually removed, so there is no advantage to "working in" to the desired depth of groove with successive sizes of dies. In fact, the work hardening that is the result of each pass of the die could be detrimental to the piece - possibly producing spalling or cracking in extreme cases. In any event, it seems to be at most a two stage proccess.
If an adequately bored and reamed tube is available, it is only a one piece operation. If not, a button is made to the correct diameter for swaging the lands, and passed through the barrel drilling to "button ream" it. It is then rifled with the "rifle button":
Excuse the coarse drawing and note that it is not to scale. The tapered ends are a few thou smaller than the bore size. The waist of the button (1) is .0015"-.002" oversize of the desired depth of groove to allow for springback in steel barrels. I am not sure that this would be neccessary in most aluminum alloys. The button's grooves (3) are of course, cut significantly undersized from the lands of the barrel to avoid marring them. The button is sweated to a piece of drill rod that serves as a pull rod by means of a post (2) inserted into the rod. I suspect that this is done so that if the pull rod snaps during the proccess it can easily be removed and replaced, whereas a mechanical connection like threading that runs contrary to the grooves could prove to be very difficult to seperate after the first time the button has been used. Even so, you will have to do something like that if you are using a hardened steel die, as hard soldering would draw the temper back to being uselessly soft. Threading is probably acceptable in your application, as I just can't see a 20-30mm diameter length steel rod failing before the aluminum tube. The reaming button is of the same configuration without the grooves.
Other pictures of buttons that I have seen have pilots, and some even have bushings fore and aft of the die, but I do not think that they are neccessary. If lubrication is an issue you could have keyways that correspond to the grooves cut into an undersized pull rod that has a section of tubing slid over it so that oil can be pumped into them, but again, I do not think that is neccessary.
Here is a simple rig, based on a vertical button rifling machine that was described to me:
It's simply a rectangular frame made of square steel tubing. A piece of tube or pipe (3lower) with a bore slightly larger than the diameter of the barrel blank (1) is slid onto the blank. The blank is then slipped in to a similar piece of tubing (3upper) that is welded to the frame, and the blank pulls against a thrust bearing (4). (3lower) then drops into a mating piece of pipe (2) that is welded to the bottom of the frame to steady the barrel blank (1). The pull rod and attached button are then drawn up through a hole in the top of the frame (5) having been earlier inserted through a corresponding hole in the bottom of the frame (not illustrated) and barrel to attach to the press head.
You will note that in the above description, it is the barrel that rotates as the button passes through it, not the other way around, and that the barrel bears against the thrust bearing at the top of the frame. This arrangement has apperantly been used for rifle barrel blanks which have very thick wall thickness in comparison to bore size, and I have some concern that the thinner wall to bore ratio expected in a 40mm tube could lead to buckling problems.
This can be overcome in several ways. The first of course, is ensuring that there is adequate lubrication to overcome any friction issues. The second is to start with a much thicker barrel blank, and the third is to anchor the bottom of the barrel while the button is being pulled through it:
This frame - made out of a heavy I or U-beam with end caps welded on - is a more elegant solution anyway, and probably the one that I would build. In this case, the barrel blank (1) has been turned down so that it has a thick (0.5-1xbore dia) flange (4) that rests in a thrust bearing (3) on the bottom end cap (2) with the pull rod being drawn out the top hole (5).
A few other things of note:
From what I have learned, lubrication and the elimination of unneccesary friction are critical both in terms of surface finish, and to avoid any tool/material failures.
It's important to remember that you are not cutting the metal, you are deforming it, and that means that the application of force in any direction may affect the finished piece. So in the case of the frame first illustrated buckling and bulging are an issue. In the case of the second frame, stretching, elongation would be issue. It may be neccesary to add additional bearings, bushings, and supports, or otherwise fine tune the proccess.
Once perfected though, you should be able to pop out a barrel every few minutes.
From the photo of the original M204 bore that was posted, the size of the grooves are incredibly large in comparison to the size of the lands. Much more so than a standard rifle barrel. All that metal has to be pushed out of the way. Wouldn't this pose a problem for the button rifling process?
Quiet said:
Yes. Bigger, deeper grooves = more pressure and friction = more problems. However, probably nothing that I would think is insurmountable by a company of the size that Mike linked his photo to. They have a huge shop and technical expertise there. With hardened steel dies instead of TC and that kind of resources, they can afford to play around a little to make it work.
Why i mention a 2 or 3 stage process is because of the size of the grooves. What i can in mind, was to actaully broach out 50% of the groove, and then
swage around the removed metal, as i am not sure that the thinwall AL tubing can handle the pressures created with swaging that much out.
Also in the 203, the groove are deeper than typical rifling in a steel barrel.
swage around the removed metal, as i am not sure that the thinwall AL tubing can handle the pressures created with swaging that much out.
Also in the 203, the groove are deeper than typical rifling in a steel barrel.
MikeH said:
Yeah, but that just means you have to support the tubing during the swaging operation. There are a couple of ways to do this:
The easiest is to "cuff" it with a piece of thick walled steel pipe that has a bore somewhat over the size of the OD of the aluminum tube. Just how much oversize, I don't know, as it will depend on how much of the aluminum is displaced during the swaging. You'd have to calculate it. In this case you would definately want to flange the tube on the bottom so that it could be extracted from the pipe - maybe a difficult proposition.
The second is to just make a steel die that supports the tubing in the same way as described for the pipe above. However, as this die can be constructed to open, there should be no extraction difficulties, so the die can be made to fit the size of the OD of the rifled tube, as long as allowances are left for extension of the aluminum tube at the top of the die. Again, the rifled tube would be flanged at the bottom.
In that way you should be able to form the tube in one go - providing that the right alloy can be found. Again, You are probably going to want to use tube that is a fair bit thicker than the expected finish size.
You're going to have to send me one of these when they are done. I'd love to see them working.
