Measuring alloy hardness by comparing ball indentations

[Alex Hamilton]

I have been casting using range scrap lead of unknown "composition" and I would like to measure its BHL hardness. The method I intend to use is to compare sizes of ball indentations against a known harness - in my case, virgin Linotype. Does anyone remember the formula for calculating BHL by comparing the size of indentations?
Many thanks,
Alex

[redhawk0]

See if this helps.

redhawk

245516

[JonB_in_Glencoe]

Hu = Hr(Dr)(Dr)/(Du)(Du)

http://www.texas-mac.com/Evaluations_and_Recommendations_for_Lead-Alloy_Hardness_Testers.html

[Alex Hamilton]

Thank you Guys. I was referring to the method described by JohnB as "Simple low-cost hardness tester"
Alex

[6bg6ga]

I realize you probably want to DIY something but why not just buy one and be done with it?

[mehavey]

It's a power function
BHN = Constant * X^(-2.164)

Where X is the impression diameter at equal pressures.
Adjust the Constant to where BHN equals your known-BHN impression diameter, then use formula for any impression at that same pressure

[Hick]

I have used the method shown in JonB's post for some time. Works great in the normal range of hardness for the alloys we use.

[mdi]

When I first started looking a checking BHN of my alloys I thought about a home made tool. But, my impression changed when I realized some factors would be difficult to do; a constant, specific pressure on a specific diameter ball for a specific time...

[6bg6ga]

When I first started looking a checking BHN of my alloys I thought about a home made tool. But, my impression changed when I realized some factors would be difficult to do; a constant, specific pressure on a specific diameter ball for a specific time...

That is why I bought the cabin tree unit

[country gent]

I have thought about a automatic center punch for a driver. A point made with around a .100 ball. Measure ball indentation, depth or size ( either would work). I believe it would give the measured impact and be accurate for most casters uses. The big thing is coming up with the conversion factor to get bhn. I have used the starrets and the punch marks in steel aluminum and copper are very uniform in size and depth across a piece. For use as a hardness tester in lead a heavier or lighter spring may be needed and a way to keep a constant tension set on the cap.

Another way I have thought about was a reloading press with the point in the die head thur a flat shell holder 1-1/2" in dia and lip1/2" thick or a veed version. to get the measured push the press wound be driven with a torque wrench. This would be a much bigger unit dedicated to testing hardness. The dies adjustment up and down might allow zeroing by adjusting its contact point in the presses leverage point

[mehavey]

The big thing is coming up with the conversion factor to get bhn.Again, see Post #6 (http://castboolits.gunloads.com/showthread.php?385341-Measuring-alloy-hardness-by-comparing-ball-indentations&p=4691442&viewfull=1#post4691442).
It's exact, save for the fact that an impact depression may create a different
deformation compared to Brinell's slow yield to static equilibrium

[Hick]

Again, see Post #6 (http://castboolits.gunloads.com/showthread.php?385341-Measuring-alloy-hardness-by-comparing-ball-indentations&p=4691442&viewfull=1#post4691442).
It's exact, save for the fact that an impact depression may create a different
deformation compared to Brinell's slow yield to static equilibrium

That's true. BUT-- if all you are doing is working with a narrow range of lead alloys (like BHN 9-22) and you have a sample that you know, you can get close enough to separate your alloys for different purposes by using the approximation given in JonB's post. Even better, if you have a leftover sample of alloy you know works well in a given firearm, you can match a new batch of alloy to the known one using the same method. So, while the truth is more complicated, the simplified method does all that is really needed.

[Petander]

FWIW:

After using a Saeco tester for 15 years ,I now can approximate the hardness of a given bullet with an anvil and a hammer.

I realised that after smashing coated bullets for a year.

[mehavey]

"....while the truth is more complicated..." (i.e., the power Equation in Post #6 (http://castboolits.gunloads.com/showthread.php?385341-Measuring-alloy-hardness-by-comparing-ball-indentations&p=4691442&viewfull=1#post4691442)), the simplified method....Actually, the simplified method is the Power Equation ... simply to 1 significant figure as the inverse ratio of squares of the diameters.

And not bad:

Actual Reference: BHN 5 Dia=0.098"
Actual BHN 25 Diameter 0.046"
Ratio of the Squares => BHN(estimate)=>23