Curious: Hardness testing question

[Typecaster]

Has anybody done a experiment to see how accurate the hardness test method in the NRA casting book is? Basic technique (IIRC, since I'm at a client's office), squeeze a large (.750" or so) ball bearing between two samples in a vise; one pure lead (BHN 5), the other unknown. Use a caliper to measure the width of the dents (the large diameter of the bearing makes it easier), and there is a formula to compare the two.

Seems to work at least well enough that known linotype tests out around BHN 20, a batch of "mystery heavy metal" dive weights and sinkers around 6.5, and various smelts of WWs in the range of 15-16, as I recall.

So if anyone used this method before buying a commercial hardness tester, how close was it?

And if anyone with a Cabine Tree tester is curious about this, I'd be happy to test 3-4 ingots (misc.; plumber's pig lead; WWs; stick-ons; and Lino) and will ship the test ingots to you at my expense for comparison. No return expected. Of course, we should post the results here for the edification of the audience...

Thanks,

Richard

[Willbird]

The basic method is used to check steel brinell hardness. They make a tool that holds a sample of known hardness and a ball bearing, and you smack it with a hammer and do the same measurement comparison between the sample which is a known brinell and the part being checked which is an unknown hardness.

Probably not as dead on accurate as a brinell tester, but good enough to be a commercially viable product.

Bill

[Typecaster]

Willbird—

In effect, that's the technique in the NRA book…by squeezing a known sample (the plumber's lead from the foundry, for all intents and purposes pure) and the unknown sample in the vise together, you're comparing the distortion for both.

My question remains—how close are the results to a commercial hardness tester?

Richard

[Willbird]

Willbird—

In effect, that's the technique in the NRA book…by squeezing a known sample (the plumber's lead from the foundry, for all intents and purposes pure) and the unknown sample in the vise together, you're comparing the distortion for both.

My question remains—how close are the results to a commercial hardness tester?

Richard

Yes I have read of it in that book. I do not have a commercial hardness tester. if anything I think the ball bearing method if used with a known alloy on one side would be more accurate, and in fact could be used to calibrate the hardness tester.

Bill

[idahoron]

Richard I have a Cabin tree and I would do it for you. Ron

[rhead]

Ditto Wllbird.
Limited only by your ability to measure the diameter of the dimples. and the purity of your standard. Both things that you can't get away from with the storebought types, they just hide the same weakness. Only weakness is the ability to measure an individual bullet.
Why does someone need to know if the hardness is 18.9 0r 20.1? What do you do different with one batch that you don't do with the otjer?

[missionary5155]

Good morning
I use the Steel Ball method here in Peru. I think it is as acurate for my purposes as using my LBT tool up NORTH. As stated about.. there is little practicle advantage of knowing the exact harness. Hardness is only a guide line to indicats "About how much pressure will that bullet base support" ABOUT is the key work. A thick base will take alot more pressure than a thin base and throw in some GOOD lube with a GOOD cast bore you can surpass the "guidelines".
Steel ball size is incidental. A 1/2" steel bearing is easier to be found.. at least down here. But BIG is better when it comes to that "Accurate" measurement. The measurment is the key... anyone with an accurate dial caliper who has used that dial caliper for 15 minutes can come up with an accurate measurement. Again if you vary 1 whole point... it is not gonna make any practicle difference. It to me is just a guideline and thats it. Shooting is the PROOF.
Miike in Peru

[Bob Krack]

I have an article by D.R.Corbin detailing the method and the mathamagical formula for calculating the Brinell hardness.

http://www.mrpc.info/docs/bultip05.pdf is the URL (courtesy of Cap'n Morgan).

Bob

[Willbird]

I used to measure quite a few things in my work, you can get very very close using a pair of calipers and a 10x magnifier. To do it more accurately we had a microscope that had a micrometer driven stage on it. if you wanted to be REALLY accurate you could measure the dimples that way.

Brinell hardness testers used in industry use optical measurement of a dimple dia caused by a calibrated amount of weight sustained for a specified amount of time.

Bill

[Typecaster]

idahoron—

Okey-dokey. Let's see how well this works. PM me with your address and I'll ship 'em up to you next week.

Thanks,

Richard

[Zbench]

All,

New to the forum, out of necessity I need to cast some buckshot.

I wanted to ask a question. As luck would have it, I actually own a Rockwell Hardness Tester. It's the twin type which can test both regular and superficial scales. I also have the various ball indenters which are used with softer metals like copper and presumably lead.

I know that there are scales to convert Brinell to other hardness values. My question is, what is the optimum hardness, in any scale, for buckshot? Since I have a very precise piece of testing equipment in my basement, no use in resorting to ball bearings, hammers and the like.

Any advice would be appreciate. If you happen to know of hardness values in any of the scales mentioned, please let me know.

Pete

[montana_charlie]

Brinell hardness testers used in industry use optical measurement of a dimple dia caused by a calibrated amount of weight sustained for a specified amount of time.That is also an exact description of the Lee tester...

[keeak]

I shot IHMSA for several years and we used " Hard Cast " as our go to load, it is not at all scientific, but when I can no longer make a mark on the bullet with my thumb nail, it is hard enough. We never did get scientific and weigh out the lead and linotype. we just melt wheel weights then add linotype untill you can no longer make a mark with your thumbnail.

[hoosierlogger]

I saw a thread on here when I was lurking, that someone made a tester using their reloading press with a weighted bag hanging on the handle to put pressure on a jig with a ball bearing that was inserted into the die holder. then measured the size of the dent, but I cant find it now.

[Typecaster]

Zbench—

First off, welcome to the asylum.

I'm sure we can come up with a Rockwell/Brinnell factor. At the very least, send me a PM (private message) and I'll send you samples from the same batch that I send to Ron.

This, I think, is getting interesting. If I use the ball bearing method to make a calculation, and Ron uses a Cabine Tree, and you use an official Rockwell hardness tester...from samples cast from the same batch...you see where this is going?

WOW! "Is this fun or what?"

Richard

[yondering]

I saw a thread on here when I was lurking, that someone made a tester using their reloading press with a weighted bag hanging on the handle to put pressure on a jig with a ball bearing that was inserted into the die holder. then measured the size of the dent, but I cant find it now.

That's what I do. A .310" ball mounted on the end of a 7/8"-14 bolt serves as the indenter, and the bullets sit on the ram, with a small flat steel piece to protect the base. I use a 35lb weight from my weight bench, hanging off a marked spot on my press handle, and measured the force exerted by the ram at one particular handle position. The handle position is marked by grinding a small notch in the ram where it lines up with the base of the press. I have a spreadsheet made up with the Brinell hardness calculations, so I can just plug in the indent diameter, and get BHN.
Instead of measuring the force exerted by the ram, one could measure samples of known hardness for comparison; maybe pure lead or linotype, and go from there.