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Old September 20, 2012, 07:25 AM   #1
mehavey
Senior Member
 
Join Date: June 17, 2010
Location: Virginia
Posts: 2,601
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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