Finding BHN

[Skink]

OK, you guys convinced me that I needed some way to measure bullet hardness. Being fundamentally frugal…cheap?...there’s no way that the old Skink was going to spring for one of those fancy store bought Brinell testers. A quick check with an engineering handbook (bought for 50 cents at the Friends of the Library sale) convinced me that it could be done on the cheap. Turns out it can, at least up to my relaxed standards. Since the method I stumbled onto didn’t turn up on a search of this forum, here’s my penny pinching BHN testing method in case there any more misers out there. According to the handbook, all you need to do is to push a ball into the test metal with a known force and then measure the diameter the dent. That ain’t rocket science, even for us liberal arts majors. A ball bearing meets the ball requirement nicely and almost all reloaders already have a decent caliper. All that remains is a good steady known force. That was a stumbling block for a while, but several blind alleys the solution turned out to be ridiculously simple…my Lee reloading press. When the handle of that Lee press is horizontal (measured with a level) its leverage is 7.24 to one. How do I know? About an hour of careful measuring demonstrated that small measured moves of the ball handle on the press moved the ram 13.812 percent as far as the ball moved. So, if I balanced that dusty 25 pound dumbbell hidden in the closet on the press handle ball, it should push the ram up with a force of 181 pounds. It’s all down hill from there. File a nice flat spot on an alloy ingot and balance it on the ram. Stick the ball bearing on the end of a case sizing die with some bullet lube. Level the press handle by screwing the die up and down in the press and then set the dumbbell on the ball handle and leave it there for a while. A good side light and an old 35 mm camera lens (remember those?) help in measuring the diameter of the dent. The rest is just math. Being fundamentally lazy, I wrote a little Qbasic program to handle it for me. How does it work? I measured some theoretically pure lead at 5 and Midway lino at 25. That’s close enough for me. Give it a try.

[Blacktail 8541]

Could have saved your self a little work if you had visited Dans' webb sight at Mountain Moulds he uses the same set up with a RCBS jr press. He will even provde a spread sheet of conversions for you . BUT GOOD JOB , I WOULD NEVER TRY TO DO THAT KIND OF CALCULATIONS MYSELF.

[BrushBuster]

I came across this el-cheapo hardness testing method provided by a poster on another forum. Have not tried it myself, but I intend to.

Post subject: Cheap hardness testing
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There's a dirt cheap test method that's widely used industrially for measuring the hardness of paint films, and I've used it with good success for lead alloy bullets. All it takes is a few art pencils from the nearest hobby shop.

Art pencils are made with a range of core hardnesses, designated (soft) 6B, 5B, 4B ... B, HB, F, H, 1H, ... 9H (hard) You'll mostly want the B pencils. Some of the H pencils can measure the hardness of aluminum alloys.

Anyhow, they're easy to use: Peel away some of the wood and expose the core. Hold the pencil straight up, and rub it on a bit of fine sandpaper to make a wadcutter tip, with sharp edges. Wipe the loose dust off on a bit of cotton, and then try to dig the shapr edge of the core into your bulet or ingot. If the lead is harder than the pencil, the pencil will just slip on the surface. If the pencil core is harder, it will cut into the lead alloy. By matching the hardness of the pencil that will cut, you can duplicate alloy hardness from batch to batch. Works great.

This pencil hardness test is actually an ASTM (American Standard Test Method), but I forget the test number. Look it up at the library if you're interested".

[MTWeatherman]

First off Skink....let me say welcome to the board.

Lyman's Cast Bullet Handbook #3 discusses a similar method...ie using a press and a ball bearing with an equal force to measure the relative indents in a piece of pure lead and the alloy...measuring the dent diameter of both and using a formula to calculate the BHN.

However, seemed to me I could use a vise to guarantee equal pressure and avoid the setup and equipment time of using a press. I take a vise and put a ball bearing between a flat piece of pure lead on one of the jaws and the unknown BHN alloy on the other (requires a bit of creative manipulation). Crush the ball bearing between the two pieces. Since the force on both pieces should be equal...you can now measure the indents and do the calculation. I've used this method and come up with values near the estimated values for various alloys...including 21 for linotype.

However, I find I really don't need to know the exact BHN...just relative hardness. I heat treat WW bullets for some handguns and if they are harder than linotype, I'm happy because the process worked. In a rifle used for hunting, I use a BHN calculated at about 13.5. So, I have cast bullets of Linotype and of the hunting alloy to be used as reference...you could do the same for any alloy of known BHN. As a quick check for unknown BHN, I put the cast bullet of it nose to nose with the known BHN (this assumes a decent meplat...if not you'd have to use the bullet base). The harder alloy will show less deformation than the softer...equal show about equal deformation. The estimate I get is close enough for my purposes. Note: this method will only work for alloyed bullets because they are less susceptible to BHN change with age...don't use heat treated bullets for reference because they do change.

So, I've found I really don't need a hardness tester. I can get a close enough BHN with some pretty primitive equipment...and in most cases a determination of relative hardness is good enough.

[Skink]

I really like that pencil idea and intend to try it.
Thanks