Different alloys. How can I mix them to obtain a desired hardness?

[John Boy]

Example .... 3 alloys on hand with measured BHNs of 12.5, 17.5, and 20
http://www.frfrogspad.com/miscellm.htm#mix

[MrHarmless]

That's a good article. I also like this one:

http://www.lasc.us/Kelter_Cast_Bullet_Alloys2.pdf

[gbrown]

I have used the lead alloy calculator over on lead and lead alloys. With a Lee lead hardness die, it has always come out good for me. At times, maybe .5 or so off, but nothing dramatic.

[MrHarmless]

I agree on the Lee hardness tester. It's been shown to be wildly accurate compared to even more expensive options. I love mine.

[Land Owner]

In the OP article, it is interesting that the product of weight times hardness when totaled (131) and divided by the total weight (8.5) equated to 15.4, which is close to the 15 BHN desired. What does that math really mean? It means 1 part of 20 BHN plus 3.5 parts of 17.5 BHN plus 4 parts of 12.5 BHN when mixed achieve 8.5 total parts at 15.4 BHN.

Using a spreadsheet (and 30 seconds to set it up): It would be easier to use 3.5 parts of 17.5 (61.25) plus 3.5 parts of 12.5 (43.75) for an exact 15 BHN (105/7).

Only in the case where the parts of 12.5 and 17.5 BHN's were insufficient would it be necessary to include a part of the 20 BHN to the mix. It is after all just proportionality.

1 "part" equals whatever quantitative amount the caster chooses (pinch, ounce, ladle, pound, etc., so long as the amount is consistent for each BHN in the mix).

Of critical importance in the OP article is knowing the exact BHN's. If BHN's are an approximation, as in the pencil test, then the alloy of the mix will also be an approximation.


A 2nd proportion of 15 BHN is 1 part 20 plus 2 parts 17.5 plus 4 parts 12.5.

A 3rd proportion of 15 BHN is 0.5 parts of 20 plus 3 parts of 17.5 plus 4 parts of 12.5

There are MANY other proportions using these three given BHN's and their given weights. A spreadsheet helps to figure out how to slice the baloney...

[Rcmaveric]

I use a sinple mixing cross.

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[lightman]

I've never gotten to hung up on hardness. Clip on wheel weights have always worked on about everything that I cast. If I ever needed more I would blend up a batch with a little type metal added.