Anyone interested in Nice Shot at $60/kg Tungsten/Tin birdshot
- Thread starter ghughes
- Start date
I remember reading about a guy in the US that was turning out bismuth through a highly modified littleton shot maker (I remember reading it took him a long time to get it right). Apparently reasonably good quality. He was doing it as a hobby and his prices on larger orders was VERY good (that is, relative to the cost of the base metal).
Of course I can't find the reference anymore....
BattleRife
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I honestly don't know where from. I just see the LME spot prices published once a week.
The melting point of bismuth is similar to that of lead. All the soft metals melt in around the same place, this is not a factor in making shot from them.
I have seen reports of people making Bi shot from littleton-type machines. It is reputed to be tricky and give poor consistency, so you remelt the malformed stuff and try it again. Nothing that would likely be consistent enough for commercial production.
Patents for commercial production methods show that large shot, #2 and bigger, I think, the pellets are cast in round ball moulds. Sound slow and expensive? You betcha! Smaller shot sizes are dropped from shot forming machines, but the shot won't form into spherical shapes if it falls into water, so they drop it into medium fraction hydrocarbon baths, which possess a certain combination of high boiling point, viscosity and surface tension, all of which are covered by the patent.
The melting point of bismuth is similar to that of lead. All the soft metals melt in around the same place, this is not a factor in making shot from them.
I have seen reports of people making Bi shot from littleton-type machines. It is reputed to be tricky and give poor consistency, so you remelt the malformed stuff and try it again. Nothing that would likely be consistent enough for commercial production.
Patents for commercial production methods show that large shot, #2 and bigger, I think, the pellets are cast in round ball moulds. Sound slow and expensive? You betcha! Smaller shot sizes are dropped from shot forming machines, but the shot won't form into spherical shapes if it falls into water, so they drop it into medium fraction hydrocarbon baths, which possess a certain combination of high boiling point, viscosity and surface tension, all of which are covered by the patent.
Another method...
Hello all,
One method that may be over looked by most is the "parallel" plate method of rolling to get a consistent size. The basic idea is that you have two plates one fixed and a second oscillating in a circular with the plates perpendicular to the ground. The top opening being larger than the bottom. For example, 2mm gap at the top and 1mm at the bottom. The idea being that the movement creates more uniform "balls" that do not pass until they have been shaped to the correct size. The trick is getting a consistent volume of metal not shape, this is controlled by the opening width at the bottom. If the volume of the sphere is to high or too low then it will never get out or fall right through.
I have seen this with extruded and rolled balls for bearings as the first step. You start with a wire and send it through rotating die with half round dimples. What comes out the other side looks like the little ball chain for a sink stopper.
The other option is to use a mill stone similar to a flour mill with a spiral groove going from the center outwards decreasing with depth as it gets to the outside. Feed the balls from the center and rotate the wheel. They will exit and will be sized correctly. It depends on how fast the spiral is and how deep the groove is to start. Easy with CNC machines now, very hard 20 years ago. The only note on both options it that you should bead or sand blast the first few inches of each so there is some grip for the balls. We used plasma spray on mill rolls in the steel mill to do the same thing.
Hope this helps some of the inventors out there.
Scott
Hello all,
One method that may be over looked by most is the "parallel" plate method of rolling to get a consistent size. The basic idea is that you have two plates one fixed and a second oscillating in a circular with the plates perpendicular to the ground. The top opening being larger than the bottom. For example, 2mm gap at the top and 1mm at the bottom. The idea being that the movement creates more uniform "balls" that do not pass until they have been shaped to the correct size. The trick is getting a consistent volume of metal not shape, this is controlled by the opening width at the bottom. If the volume of the sphere is to high or too low then it will never get out or fall right through.
I have seen this with extruded and rolled balls for bearings as the first step. You start with a wire and send it through rotating die with half round dimples. What comes out the other side looks like the little ball chain for a sink stopper.
The other option is to use a mill stone similar to a flour mill with a spiral groove going from the center outwards decreasing with depth as it gets to the outside. Feed the balls from the center and rotate the wheel. They will exit and will be sized correctly. It depends on how fast the spiral is and how deep the groove is to start. Easy with CNC machines now, very hard 20 years ago. The only note on both options it that you should bead or sand blast the first few inches of each so there is some grip for the balls. We used plasma spray on mill rolls in the steel mill to do the same thing.
Hope this helps some of the inventors out there.
Scott
