Alloying the metal is pretty straightforward and not hard, Take respiratory precautions and be sure you wash your hands before sucking your fingers but otherwise just get the lead plenty hot and stir your antimony in with a metal rod while tossing in sawdust and beeswax to keep the top fluxed. You'll see when the metals alloy and then you add more sawdust and wax and stir for a few more minutes then done!
Ball mill media
Posted 21 February 2017 - 07:44 PM
Posted 21 February 2017 - 08:40 PM
I think if you talk to the guys manufacturing commercial amounts of 1/2" media you'll find they use 50/50 lead to linotype which would produce lead with 6% antimony which is hard enough. I used 100% linotype (12% antimony) when I made my media and its very hard and puts a lot of undue stress on your mold and is miserable to cut the sprues off the ball but produces excellent media. Pure antimony can be added to molten lead but takes a certain amount of flux and must be done at about 600 degrees for good results. A process probably best left for a smelter. That's the reason people use linotype or other "type set" metal for the antimony content, the alloying work is already done for you . I can tell you after pouring and cutting off sprues for 100 lbs of media my hands cramped up and hurt for about a week (I'm an old guy). It was a fun learning experience but I'll never do it again. After you consider your time, materials, blisters and lead spills on the garage porch floor, you'll find the price these guys charge on the forum and elsewhere for the finished product a real deal and worth every penny! Kurt
I've cast lead fishing jigs/sinkers for decades. Not difficult, but proper tools help a lot. When I got the bug to cast my own media I already had a .50 cal mold for round balls. I poked around a little bit and discovered there's a few "levels" of type alloys that are available.
Linotype, despite its reputation as a hard alloy, is the softest and most available. Increasing in hardness and scarcity are monotype and then foundry type. I bought into a pile of foundry type and cast my media straight, exploiting the superior hardness without dilution. As a result I didn't feel the need to quench though the finished product would certainly have been even harder. Out of the mold the hardness made the cast so brittle sprues snapped off very cleanly when fresh. Once cooled even a bit they were almost impossible to snap much less cut. My media is very satisfactory and will likely last as long as I want to use it. I guess we'll see....
There's also a tradeoff in media. You can't have maximum mass AND maximum hardness. As your lead alloy increases in hardness those very additions make the alloy less dense piece for piece. I don't have a calculation for hardness vs mass in a grinding media but I'll bet there is a tipping point and I don't know where that might be. It's probably dependent on what you're grinding and how far you want to take it.
Casting your own isn't difficult and can keep you in media as long as you've got raw material.
Posted 21 February 2017 - 08:50 PM
"I don't have a calculation for hardness vs mass in a grinding media but I'll bet there is a tipping point and I don't know where that might be."
I don't either, Otto, but I'm betting it makes no difference. The reason I say that is that the next less dense medium would be steel (stainless steel), and that's VERY much less-dense than any lead alloy you could think of.
Posted 22 February 2017 - 07:54 AM
Oh the joys of casting lead..
Wheel weights.. yak they are down to almost 50% trash..
lead from flashing. not bad , but big and dirty
I get my lead off of ebay in precast ignots now. I get an already hard blend. and then add linotype to it.
I've poured straight lino, and used foundry. Both I didn't like and didn't get my moneys worth in both stress and tool wear.
I can get 1000 lbs of media out of a mold now which is acceptable. I have my eye on an automatic caster at the moment. It's hard to drop lead and run machines at the same time.
I do water drop mine/ dry them, and fill a mill jar up darn near full and then run them overnight to clean them up. Then I pick out all the oddball/ junk i can find.
It's work , but I have a pretty good system now after running 5 or 6 thousand lbs of it.
I believe united nuclear gets mine.. and some other guys as well.
Once you get clean materials and a nice groove it's not too bad of work.. The first couple 1000 lbs really really sucked as I figured it out.
Pyro tools made by a pyro.
Light it up!
Posted Yesterday, 05:45 AM
Yep. Lead ain't what it used to be.... I've got a pretty good pile of soft and foundry waiting for reuse. Precast ingots are a crap shoot. Might have zinc mixed in among other stuff. Unless you're tight with your supply you'll never know until you melt it down.
I don't do the kind of volume you do Caleb so sacrificing a mold here and there doesn't hurt so much. I'm currently considering casting lead cylpebs in a home brew mold. Not hard to make and easy to replicate.
Posted Today, 07:09 AM
What i am finding is the specific gravity of Zinc is less than Lead, but more than Ceramic. What i was thinking that there might be a contamination problem with Zinc since it seemed like everyone was dodgen it.
There are very few problems that cant be solved with explosives.
Explosives are a bang up job.
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