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Old September 20, 2012, 07:25 AM   #1
mehavey
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Lee Hardness Tester Recalibration

Anyone else run into this?

I picked up a Lee Hardness Tester 6-8 weeks ago, did a quick trial to figure out how to set up the microscope/prepare the samples/run the process using an adjustable microscope stand for steadiness/strong quartering light for impression dimple edge sharpness... then put it away.

I hauled it out tonight after last week's casting session w/ a new Paul Jones 45 Creedmore mould and one from Hoch using two RotoMetal-supplied alloys: Lyman #2 and 1-to-30.

First sample was a Lyman#2 bullet (with filed-flat surface), 30 seconds in the press and under the microscope it went: Dead on 0.059" dimple diameter for a BHN of 14.9 -- Great (!)
http://www.frfrogspad.com/miscellm.htm#Brinell

Then the 1:30 alloy: 0.093" diameter --> BHN 5.8 (Huh? it's supposed to be 9)
So... another 1:30 bullet and another test: 0.094" --> BHN 5.7 (!!!??)

But before I call RotoMetals to yell & scream, I go out to the garage and pick out a pure (really pure) lead paper patch cast-off bullet from a session two years ago.

Another test: Pure Lead: 0.120" diameter ...and literally off the Lee reference scale. Something's wrong.

So I do a simple straight-line projection between the Lyman#2/0.059"/14.9BHN point (which I hope is right)
and the PureLead/0.120"/5.0BHN which I know is right
to get the following:


Lo and behold, the 1:30 alloy is now exactly where it belongs.



Have I missed something here?

.
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Old September 20, 2012, 10:47 AM   #2
snuffy
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In my experience, that 30-1 alloy should NOT be that hard. Tin just does not harden pure lead all that much. Where did you get that 9.1 figure for the 30-1 alloy? I would say that the reading you got for the 30-1 from the lee tester was correct.

Tin does 2 things for lead when it's the ONLY other metal in pure lead. It makes the lead melt at lower temps, allows it to be more liquid so it fills molds better, and toughens the metal. Okay that's 3 things! But it does not harden it much.

Now if there's antimony in the lead, tin combines with the antimony to really harden it. In fact the tin HAS to be included, or the antimony won't go into solution with the lead, it exists as separate crystals surrounded by pure lead. There's a ratio, that I can't remember right now, that has to be maintained, or the antimony won't mix with the lead.
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Old September 20, 2012, 11:14 AM   #3
mehavey
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Quote:
Where did you get that 9.1 figure for the 30-1 alloy?
See Los Angles Silhouette Club note here about 1/3 down the page/left side. I tend to reference these guys for any number of reasons and have found them to reflect the True Cross on any number of Cast Bullet subjects.

See also PnJ Resources Link here.

I was also concerned that the BHN of the 30:1 alloy was truely soft -- until I baselined against the pure reactor-shielding lead I've been carrying around since my misspent youth. That measurement told me waht was going on and how to "fix" it.

If there's a better BHN alloy listing that those cited above, I'll gladly use it.
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Old September 20, 2012, 04:54 PM   #4
sidewindr
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From what I know of the alloys and how they co-mingle, I believe what snuffy said was correct. Tin would MAYBE give 1-2 bhn hardness on its own once you get up to 1-2ish%, unless just by tin being harder than lead, it jumps the hardness a couple points right away. if that makes any sense. I think the 30-1 is testing about right, but mayber it could go up 1. I don't think that projection line is going to be straight. The radius of the ball has to be taken into account. The part that pushes into the ingot or bullet would have to be a sharp cone for the line to follow inline. My guess anyway
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Old September 29, 2012, 09:40 PM   #5
Cary
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Mehavey that is interesting. I checked my "RCBS Cast Bullet Manual" and they do not list the BHN for 30:1 but they do list 20:1 Lead/Tin as having a BHN of 10. There looks to be some disagreement on the subject. My "Lyman Cast Bullet Handbook" also does not list 30:1. It lists 10:1 as having a BHN of 11.5. As far as calibration for your Lee Hardness Tester I don't believe there is one. If the ball that is pressed into the test alloy is of correct size then the only variable would be the spring pressure on the ball and the amount of time the pressure is applied. I believe over time spring pressure will deteriorate if kept under stress. How long that would take I have no idea. If you read the tests conducted by the Los Angles Silhouette Club on the different hardness testers you will find the Lee Tester came out very favorable in consistency. I do have one of the Lee Hardness Testers and am pleased with the performance.
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