Superhard Question

[Jeff82]

I just reduced ten pounds of Rotometals Superhard (30% antimony / 70% Lead) into 0.5 lb ingots for blending alloy. When I weighted the ingots I was surprized to find that the Superhard mixture was about 77% of the weight of pure lead.

I've always assumed that when blending alloy the percentages are based on weight, not volume. With wheelweights and linotype, the difference between the two shouldn't be too significant. However, with Superhard I think I'd need to figure that the antimony content by weight is more like about 23% and blend it based on that percentage.

Am I correct?

Thanks in advance.

[Defcon-One]

Rotometals Superhard (30% antimony/70% Lead)

I'd Blend by weight using their numbers!

[runfiverun]

that means if you have 100 lbs of superhard you have 30 lbs of antimony and 70 lbs of lead.

in the whole [volume] antimony doesn't weigh as much as lead per cubic measurement.
specific gravity.
same as alloy percentages 2/6/92 ='s 2 lbs of tin/6 lbs of antimony/and 92 lbs of lead makes 100 lbs of alloy.

[Jeff82]

I think I'm missing the point.

If I have 100 lbs of Superhard, which is 30% antimony 70% lead. That 100 lbs of Superhard will make one large ingot that this about 1.3x the size of a pure lead ingot.

If I then mold the Superhard into 1-lbs sized ingots (based on the weight of lead), I'd actually have 130 1-lb ingots of Superhard, and 100 1-lb ingots of pure lead. This is what I actually did.

Now, if I want to blend these with the lead to form an alloy that has 3% antimony, I'd need to add 1 lbs of Superhard to 9 lbs of lead.

By weight, this would be about 1.3 ingots of Superhard to 9 ingots of pure lead.

By volume, this would be about 1 ingot of Superhard to 9 ingots of lead.

I think that measuring by weight using 1.3 ingots of Superhard to 9 ingots of lead is the correct calculation, but I'm not sure, since I'm not sure how the Superhard 30% antimony figure is calculated.


Sorry for the confusion, but..., I'm confused.

[bumpo628]

Blending alloys is done by weight.

Just weigh your superhard (SH) ingots and adjust your ratios accordingly.
To use your numbers, a "1/2 pound sized" SH ingot weighs 77% of a lead ingot or .385 lbs. You still need to use a 1:9 ratio of SH to Pure to get the 3% antimony alloy you want. (9) x (.385) lbs is = 3.465 lbs. So, you would just use about 3.5 pounds of pure for every SH ingot.

[cbrick]

With wheelweights and linotype, the difference between the two shouldn't be too significant.

Perhaps this is where your confusion is comming from. With a max of 3% Sb and 96%+ Pb in WW and lino at 12% Sb, 4% Sn and 84% Pb there is a significant weight difference.

Bumpo is correct, alloys are blended by weight. 3.5 pounds of pure and 1 pound of SH will get you the 3% Sb alloy your looking for.

Rick

[Jeff82]

Thanks. This helps.

--Jeff

[runfiverun]

no you had it right, you were just confusing mass [volume/size] for weight.
but you did find out why adding more antimony makes bigger boolits that weigh less.

[Defcon-One]

I'd Blend by Weight using their numbers!

I said it first and it is a rule, like a law of nature for alloying lead!

To answer your latest question, a 1 lb. sized ingot of superhard is not the same size as a 1 lb. sized ingot of lead!

Or, another way to say it is, a 1 lb. lead ingot mold will not throw out 1 lb. ingots of Superhard! So you don't have 130 1-lb ingots of Superhard, do you? They are actually well under 1 lb. each!

My answer is "Volume doesn't matter, use the actual weight"!

[bumpo628]

Bumpo is correct, alloys are blended by weight. 3.5 pounds of pure and 1 pound of SH will get you the 3% Sb alloy your looking for.

I know what you meant, but there is a little error with your "1 pound" statement. I just wanted to make sure the OP doesn't get mixed up with the difference between your post and mine.

It should be:
0.385 lbs superhard + 3.465 lbs of pure lead = alloy with 3% antimony, 97% lead
In other words, any 1:9 ratio will get you there.