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Machining Bismuth?

Never machined bismuth but if it is really brittle it will be like machining ceramic. Easy to drill a hole and have it blow out on the exit. They make special drills for ceramic that look like a spear that helps with that blow out. We use mostly adaptive tool paths to avoid chipping. Not sure if this helps. What do you have to do to the material?
 
No experience, but found this:

At temperatures from -196 to 0C the specific elongation and reduction in section are
equal to zero. At t > 0C these characteristics, particularly the reduction in section, increase sharply,
reaching a maximum at 50-100C (0.6-0.7)T m, increasing with decreasing strain rates. This is very important, since the smallest strain rate induces a sharp reduction of plasticity; the temperature-rate conditions in pressure treatments of bismuth must be maintained very precisely.

So, maybe heating it up a bit (don't go too hot; it melts at 520F) would help. The strain rate comment means cutting slower is better, but dunno how practical that would be.
 
I cast it to near on size, need to clean off the sprues and maybe a light finish pass. Turns out this stuff grows when it solidifies. I might try quenching it in an attempt to get smaller grains.
 
Bismuth is a heavy metal, with heavy metal dangers to people. Not much problem in the solid but dust can be inhaled and cause problems. There is no real cure for heavy metal poisoning.
The only way to eliminate symptoms is to die.
Bill D
 
Bismuth is a heavy metal, with heavy metal dangers to people. Not much problem in the solid but dust can be inhaled and cause problems. There is no real cure for heavy metal poisoning.
The only way to eliminate symptoms is to die.
Bill D
Bismuth is non toxic , used in non toxic shot
In fact it’s the main ingredient in pepto bismol
I’m sure if you ate enough it would hurt you though
 
out of curiosity: what is the component for? some electrical application? does grain size matter?
 
It's a sample holder that will go into the core of a nuclear reactor. Grain size doesn't really matter, but i think if I can get smaller grains it might not chip out as bad.
 
Talking out of my ass here but I look at some people's (good) hobby mills that have 24krpm spindles and they use small endmills at high speed to take stupidly small chips at a decent feed rate. Those tiny chips seem to me like they would prevent some of the "chunking" issues I would otherwise expect with bismuth.
 
I heated it in my kiln at 250C for 3 hours and quenched in water. Machines much better. Going to try it with oil. Possibly try a soak in liquid nitrogen..
 
Thanks for letting me know my concerns about heavy metal poisoning were over cautious. I just wanted to let the OP know it could be a problem. Turns out Bismuth is the least dangerous of all the heavy metals.
Still I would wear a dust mask if making dust. Metal dust may not be dangerous chemically but it can still cause lung problems down the road.
Bill D
 








 
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