partsproduction
Titanium
- Joined
- Aug 22, 2011
- Location
- Oregon coast
Having mentioned earlier that I'd purchased one of the .380 push type rifling buttons in ebay a while ago I thought it good to mention my first experiences with it.
The button came with instructions for $250 which included shipping. They are obviously being made commercially in Eastern Europe probably for some government arms factory, but that's just a guess.
But the reason I think that is that it is a very nicely made button. One end has a green hard substance painted on which may be a solid lubricant.
I emailed the fellow back and forth pumping him for info about what lubrication to use in the tube but he said they used a "special" lubricant which he could not sell. He did suggest a molybdenum powder, actually micro fine so that it comes out of the tube like tooth paste but when you touch it it is obviously a powder. This I mixed with MolyDee into a thick paste.
The blank;
I made the blank out of some 1 1/4" diameter 416A. The variables are blank diameter and bore size. With a thin wall the bore could be far smaller than with a thick wall, but the riflings may not fill out if the wall just bulges out, the metal must be restrained from bulging so the metal can move into the lands I recon. With a bigger blank I figure there is more constriction but bore size is more critical.
The directions said to make a blank about 1" diameter and drill a .344" hole through it, and follow that with a .348" reamer. Well, .348 is an S reamer but not having one I found the closest oddball decimal reamer that was just slightly larger at .353" and ground that down with my Darex end mill grinder, finished right at .348". But there were probably enough errors in my grinding job that the finished hole came out a close sliding fit for a .348 gage pin. If the hole had been exactly .348 that gage pin would not have fit without force.
The directions said to lap the hole and get it as smooth as possible, which I did with a split lap, and when done a .349 pin would enter the hole, too big. Well, I reasoned, too big means less chance of catastrophic failure so for R&D it's good.
To push the button, first of all the button needs to start and stay straight in the axis of the hole, so measurements showed a .360" hole would just clear, so that's what I made a counter bore to being long enough so the whole button fit flush with the end, green end out.
The actual pusher needed to be over 6" long so I bought one made of solid carbide from Israel, and made a special collar to hold it square with the hydraulic press table on the ram, the ram end of the collar I bored to fit 2" up over it thus holding it from trying to go sideways under pressure. At the bottom of that hole I put a needle thrust bearing to allow turning.
The barrel blank itself I threaded into a 3" diameter donut about .700 thick, the counterbore being at the donut end so that the thrust was supported down from above for better balance of force, I could have done it the other way but then there would have been two 6" long items opposing each other in the middle. The instructions said 5 tons should work and though the press is 90 ton the motorized pump delivers only 5-10.
Anyway, I was surprised at how easy the push went, and the bore is rifled but the lands are not as high as I would like. That button did come out pretty warm though.
The riflings are distinct the whole length of the bore so I know the quality of the bore was acceptable albeit too large. In the near future I hope to grind the reamer to .3465" and hone to .3475", as I don't know what the relationship is between enough and too much material to move. I know that with knurls a .001" increase in blank diameter will raise the finished knurl to .003 higher, but because the groove diameter is three times as wide as the land diameter a thousandth and a half may be too much. Once the exact bore diameter is known it should be repeatable.
I'd like to find out what the minimum OD the blank can be and still form good riflings in it, as otherwise a lot of time is wasted turning away metal for no good reason. It might be possible to press a larger tube over the blank to help restrain the pressure too, and then press that off when done, the truth is I have no idea how much concentric restriction is needed.
I tried to take photographs but none of them came out good enough. When I get really high quality riflings I'll try again to take photos.
All of this has been for my own education, I have no desire to go into the barrel making business.
The button came with instructions for $250 which included shipping. They are obviously being made commercially in Eastern Europe probably for some government arms factory, but that's just a guess.
But the reason I think that is that it is a very nicely made button. One end has a green hard substance painted on which may be a solid lubricant.
I emailed the fellow back and forth pumping him for info about what lubrication to use in the tube but he said they used a "special" lubricant which he could not sell. He did suggest a molybdenum powder, actually micro fine so that it comes out of the tube like tooth paste but when you touch it it is obviously a powder. This I mixed with MolyDee into a thick paste.
The blank;
I made the blank out of some 1 1/4" diameter 416A. The variables are blank diameter and bore size. With a thin wall the bore could be far smaller than with a thick wall, but the riflings may not fill out if the wall just bulges out, the metal must be restrained from bulging so the metal can move into the lands I recon. With a bigger blank I figure there is more constriction but bore size is more critical.
The directions said to make a blank about 1" diameter and drill a .344" hole through it, and follow that with a .348" reamer. Well, .348 is an S reamer but not having one I found the closest oddball decimal reamer that was just slightly larger at .353" and ground that down with my Darex end mill grinder, finished right at .348". But there were probably enough errors in my grinding job that the finished hole came out a close sliding fit for a .348 gage pin. If the hole had been exactly .348 that gage pin would not have fit without force.
The directions said to lap the hole and get it as smooth as possible, which I did with a split lap, and when done a .349 pin would enter the hole, too big. Well, I reasoned, too big means less chance of catastrophic failure so for R&D it's good.
To push the button, first of all the button needs to start and stay straight in the axis of the hole, so measurements showed a .360" hole would just clear, so that's what I made a counter bore to being long enough so the whole button fit flush with the end, green end out.
The actual pusher needed to be over 6" long so I bought one made of solid carbide from Israel, and made a special collar to hold it square with the hydraulic press table on the ram, the ram end of the collar I bored to fit 2" up over it thus holding it from trying to go sideways under pressure. At the bottom of that hole I put a needle thrust bearing to allow turning.
The barrel blank itself I threaded into a 3" diameter donut about .700 thick, the counterbore being at the donut end so that the thrust was supported down from above for better balance of force, I could have done it the other way but then there would have been two 6" long items opposing each other in the middle. The instructions said 5 tons should work and though the press is 90 ton the motorized pump delivers only 5-10.
Anyway, I was surprised at how easy the push went, and the bore is rifled but the lands are not as high as I would like. That button did come out pretty warm though.
The riflings are distinct the whole length of the bore so I know the quality of the bore was acceptable albeit too large. In the near future I hope to grind the reamer to .3465" and hone to .3475", as I don't know what the relationship is between enough and too much material to move. I know that with knurls a .001" increase in blank diameter will raise the finished knurl to .003 higher, but because the groove diameter is three times as wide as the land diameter a thousandth and a half may be too much. Once the exact bore diameter is known it should be repeatable.
I'd like to find out what the minimum OD the blank can be and still form good riflings in it, as otherwise a lot of time is wasted turning away metal for no good reason. It might be possible to press a larger tube over the blank to help restrain the pressure too, and then press that off when done, the truth is I have no idea how much concentric restriction is needed.
I tried to take photographs but none of them came out good enough. When I get really high quality riflings I'll try again to take photos.
All of this has been for my own education, I have no desire to go into the barrel making business.
It's expensive in money and time.
