montana_charlie
09-13-2008, 03:14 PM
I grabbed the Excel file you attached to this post http://castboolits.gunloads.com/showpost.php?p=386889&postcount=2 .
I fiddled with it until I thought I had it figured out, then I used it to try to correct some 'bad alloy' I had made.
This mix was the result of adding some tin I had bought (as pure tin) to make 30:1 alloy. It didn't produce encouraging results when checked with a Lee hardness tester, but I (eventually) found out the tester was faulty. So. I just went by my math, and assumed I had the right hardness. Then, I contacted the tin seller (a year later) to see if he was still in business. His reply made me start to wonder about the purity of the original batch of tin. It seemed there was a probability that it was 50/50.
By now, I had decided to start using 20:1, so I did the math to make this batch match that ratio...which meant adding a lot of the (now) 50/50 stuff.
Lee was still confused, but I expected that.
Then comes news that...oops!...that probably WAS pure tin to start with.
Believing I was onto the reason the Lee tester gave me unexpected results, I did more math to remix part of the screwy batch, using numbers that corresponded to using pure instead of 50/50...and went happily on my way with (what I assumed to be) good 20:1.
Time passed, and I forgot how much of what I had decided to add to the 'screwy' batch to make the 'good' batch.
In the meantime, I had traded my Lee tester for a new one...and it seems to work correctly. So, I now had a reason to 'knuckle down', 'get serious', and 'quit ******* around' with mystery alloy.
I put both piles under the Lee, and came up with (what I believe to be) accurate hardness figures for both.
The results said I had two piles of alloy...and I don't (really) know what is in either of them.
The original stuff, which has been mixed twice, tests at BHN 11.8...and the 'corrected 20:1' shows BHN 8.2.
Knowing that I am only dealing with lead and tin, I made some educated guesses about what percentages I had in each pile. That meant I had a pile of 40:1 (2.5/97.5 tin/lead)...and a pile of alloy that could probably be called something like 15/85 tin/lead.
Plugging those figures into your Excel tool, I was shooting for 20 pounds of 20:1, with a BHN of 10. It assured me that 16 pounds of the 'soft' stuff and 4 pounds of the 'hard' stuff would make me happy.
The result has a BHN of 9...same as 30:1.
Can you tell me what I overlooked?
I'm not asking what I should add to make the alloy I want.
I am asking what I am doing wrong when using the application.
CM
I fiddled with it until I thought I had it figured out, then I used it to try to correct some 'bad alloy' I had made.
This mix was the result of adding some tin I had bought (as pure tin) to make 30:1 alloy. It didn't produce encouraging results when checked with a Lee hardness tester, but I (eventually) found out the tester was faulty. So. I just went by my math, and assumed I had the right hardness. Then, I contacted the tin seller (a year later) to see if he was still in business. His reply made me start to wonder about the purity of the original batch of tin. It seemed there was a probability that it was 50/50.
By now, I had decided to start using 20:1, so I did the math to make this batch match that ratio...which meant adding a lot of the (now) 50/50 stuff.
Lee was still confused, but I expected that.
Then comes news that...oops!...that probably WAS pure tin to start with.
Believing I was onto the reason the Lee tester gave me unexpected results, I did more math to remix part of the screwy batch, using numbers that corresponded to using pure instead of 50/50...and went happily on my way with (what I assumed to be) good 20:1.
Time passed, and I forgot how much of what I had decided to add to the 'screwy' batch to make the 'good' batch.
In the meantime, I had traded my Lee tester for a new one...and it seems to work correctly. So, I now had a reason to 'knuckle down', 'get serious', and 'quit ******* around' with mystery alloy.
I put both piles under the Lee, and came up with (what I believe to be) accurate hardness figures for both.
The results said I had two piles of alloy...and I don't (really) know what is in either of them.
The original stuff, which has been mixed twice, tests at BHN 11.8...and the 'corrected 20:1' shows BHN 8.2.
Knowing that I am only dealing with lead and tin, I made some educated guesses about what percentages I had in each pile. That meant I had a pile of 40:1 (2.5/97.5 tin/lead)...and a pile of alloy that could probably be called something like 15/85 tin/lead.
Plugging those figures into your Excel tool, I was shooting for 20 pounds of 20:1, with a BHN of 10. It assured me that 16 pounds of the 'soft' stuff and 4 pounds of the 'hard' stuff would make me happy.
The result has a BHN of 9...same as 30:1.
Can you tell me what I overlooked?
I'm not asking what I should add to make the alloy I want.
I am asking what I am doing wrong when using the application.
CM