How to build a BHN tester ???

[JohnH]

I brought home an arbor press today and would like to make it up into a BHN tester I can put most any peice of scrap into. What do I need?

[JohnH]

I did a search and found the answers I need, Thanks anyway, John

[Goatlips]

Care to share your finds, John?

Goatlips

[randyrat]

I know you need a 5/32 ball and a scale, but, consistancy is tough to come by, just ask Richard Lee (second addition). I ended up buying a tester $47 Good luck and keep us up to date on this.

[4thebrdz]

What I did- 24" of 1/2" copper pipe. A punch that would fit the pipe with the tip flattened. Drop Punch down pipe on to PURE LEAD and measure. Then try Different alloys and trecord tjhe difference in the impression. Not too scientific.

[bigborefan]

Randyrat,
I use the ball bearing and scale method and you'd be surprised at how accurate it is. When I test ingots from the same alloy, they come out with the exact same size indentation every time. Using the given chart calculations, my linotype comes out to 22 BHN, my #2 alloy comes out at 15BHN and my pure lead comes out in the high 4BHN. All comparable to what they should come out to.

[JohnH]

Goatlips, Basically comparator BHN testers work on this idea, apply a given load for a given time to pure lead. Measure the deformation. Then apply the same load to test sample for same time duration. Measure the deformation. Divide the pure lead sample deformation by the test sample deformation, square the result and multiply by 5. The standard is to apply a load of 200 pounds on a 10mm ball, time seems to be anything between 5 and 30 seconds. This forms an indentation, measure the diameters and do the math. Example:

.190/.130=1.46
1.46 x 1.46 = 2.13
2.13 x 5 = 10.66
Simple enough.

But like Lee, I'm not getting answers that are consistant. On a known sample of pure lead I get everything between .175 and .220 with .190 being the most common measurement. But with a spread like that for 10 tests, it raises some doubts in my mind. I've done this enough now that I'm sure that surface condition can affect readings. A smooth or slick surface gives better readings than one which has any kind of wrinkle or wave.

Doing a search of "BHN" yeilded 800+ results. On about page 17 there was a thread that discussed all this. David R has one of Buckshots testers (so do I) He mentioned changing the ball size to one smaller (Buckshot used a 7/16 ball on mine) to see if he could get more consistant readings. (seems he too has had some trouble with the method but didn't elaborate)

Today I took a 5/16 ball and tacked to a small plate and am going to use a scale on the arbor plate to do tests. All I want is reliable repeatability.

I must say that I am quite pleased with the Buckshot tester I have, it works good on bullets, but it works in the press which is not too scrap metal friendly. I'm wanting a tester or method that I can use on most any lead that shows up here, I'll keep this updated, John

[JohnH]

Randyrat,
I use the ball bearing and scale method and you'd be surprised at how accurate it is. When I test ingots from the same alloy, they come out with the exact same size indentation every time. Using the given chart calculations, my linotype comes out to 22 BHN, my #2 alloy comes out at 15BHN and my pure lead comes out in the high 4BHN. All comparable to what they should come out to.


I agree, the method is quite accurate, but I find that the harder the metal the better or more consistant the readings are. Trouble comes at dead soft, which is the base line. If that measurement is faulty, then all else is for naught

[garandsrus]

Here are two ways that I have saved. I didn't invent either :)

Staple Gun:

A Simple Method For The Determination of Alloy Hardness By: David Berry

This describes a method for the determination of lead alloy hardness. It is a simple, quick, and economical means to test hardness of unknown alloys, and I have found it to be reliable and accurate.

Using a common staple gun, I have found that measuring the penetration of the staple into the alloy can be used to determine relative hardness when compared to a series of "standard" known lead alloys. I simply inject a staple into the sample and measure the post of the staple that protrudes. I obtain 5 readings on each known standard, average them and prepare a calibration chart versus known BHN values. A sample chart is shown below. Unknowns are then subjected to the same procedure and the resulting measurements are compared on the chart to determine relative hardness.

ALLOY 1 2 3 4 5 Ave BHN
Lead 0.102 0.107 0.115 0.109 0.12 0.111 5
Wheel weight 0.209 0.18 0.186 0.177 0.186 0.188 9
2-6 Alloy 0.223 0.216 0.217 0.19 0.214 0.212 15
Linotype 0.255 0.24 0.238 0.258 0.234 0.245 22
5 readings for each alloy in inches
Arrow T-50 stapler
3/8" staples



I first started working on 1 pound ingots of the same size, but found that size or shape is not all that important, the sample just needs to be large enough to hold the staple gun onto it. I apply about 20 pounds of pressure on each sample (determined with a bathroom scale) while I inject the staple. I have used a Bostich electric staple gun and this works well also. A 3/8 inch staple is about the largest that can be used as longer staples deform. This can be overcome by measuring the actual penetration by subtracting the protrusion as measured above , from the total length of the staple post.

Each staple gun must of course be calibrated as will the batch of staples being used.

I find this to be an extremely easy method to determine alloy hardness, and by measuring several samples have determined it to be very reliable and fairly accurate. It works very well on odd sample shapes and sizes.

Ball Bearing Author unknown...

You need about 2 pounds or so of pure lead, your test lead and a steel ball bearing and a vise and a set of calipers/micrometer and that is it.

To get the pure lead you can find it in a metal supply shop but it runs about 3-4 bucks a pound or you can save the stick on weights when you find them in your bucket of wheel weights. I bought a couple of pounds to see what the difference was between it and the stick on version and the bhn number is about 5.2 or 5.3 instead of the 5 for pure lead, so close enough.

Drop by a bearing shop and pick up a 1" steel ball bearing and that costs about 2 bucks or so.

Melt the pure lead(stickon weights)in a muffin tin and your test lead in the one muffin slot next to it. I waited a day to test because I am anal that way.

Pad the vise with aluminum or steel on the jaws so that the lead doesn't dig into the teeth of the jaws. Hold up the lead in one hand and the test lead on the other jaw and slowly squeeze the two together with the ball bearing in the middle. Just squeeze till there is a good dent on both surfaces of the lead or about 1/5 or the way in on both sides of the ball bearing.

Here is the formula BHN= 5 X (lead dia./test dia.)^2

With the calipers measure the diameter of the indent in each of the leads and plug in the values.

I had some WW and an unknown lead from a Radiator shop that I wanted to test and here are the results.

Diameter in Lead=0.479
Diameter in WW=0.325

So 5 x (0.479/0.325)^2 and that gives 10.8 BHN where it should be for air cooled Wheel Weights.

I had my friend test the WW on his Lee Hardness tester and he came up with 11so close enough.

Unknown lead from radiator shop

Dia. in Lead=0.520
Dia. in Unknown=0.279

So 5 x (0.520/0.279)^2 which gives us 17.4 BHN

I knew it was harder just with the old thumb nail test but I had no idea it was that hard. Again on the lee it came back as 17 BHN



I haven't tried either method but I like the idea that the second will give you an accurate reading without requiring precise pressure for a given time...

John

[Larry Gibson]

I use the ball bearing squeezed between lead and the alloy in the vise test. It's been working very consistantly for me for 30+ years.

Larry Gibson

[38 Super Auto]

I brought home an arbor press today and would like to make it up into a BHN tester I can put most any peice of scrap into. What do I need?

I'd take a page from the Cabin Tree hardness tester. The unit measures deflection of a spring loaded bolt using a machinist's dial indicator: harder allows will deform less and result in more movement. Similarly softer allows will deform more and move less. It's a sweet rig.

As other guys here said, you'll need to obtain alloy samples of known hardness for calibration.

http://www.castingstuff.com/cabinetree_loading_products.htm



:coffee: