Sloffie
06-13-2012, 06:38 AM
I have had a quick look around and hardness testers are expensive. But what makes them expensive I believe is their precision and that they have some kind of recording system. BUT the basics of how a Brinell Hardness tester works is VERY simple.
http://www.hardnesstesters.com/image.asbx?AttributeFileId=6f7f900a-6810-48d7-a118-2fd7871d0ce6
http://www.hardnesstesters.com/Applications/Brinell-Hardness-Testing.aspx
Basically you take a hard sphere with a known diameter. Then you place it on the specimen and you apply a load. Then you measure the diameter of the indentation and you plug it into the above formula and calculate the Brinell Hardness.
Now I was thinking, why can one not build one? It should be rather easy. Especially for lead as it is softer than steel. Get a 8mm or whatever ball bearing, get a piece of steel tube with an internal diameter just over 8mm. Secure that in a vertical position. Then, make a ram with a platform where you can place a mass piece.
Put the ball bearing into the tube and hold it with your finger so it does not drop out. Place an ingot under the tube so the ball bearing rests on the ingot. Do not drop the BB into the tube as it will dent the lead, giving you a false reading.
Then slide the ram into the tube (the weight of the ram should be known) and place the weights on the platform. Then leave it for some time (this can be experimentally determined when the indentation stops increasing) and then remove everything and measure the diameter of the indentation on the lead.
Take the weight of the mass pieces in Kilogram and plug that and the diameters into the equation.
In theory you should then have the Brinnel Hardness value for your lead.
Here is another thought. The DIY device will not be as accurate or precise as proper lab equipment, BUT it does not have to be. Firstly you only need a rough figure for harness. It does not matter if it is 10 BHN or 11 BHN.
If I want to cast for my .303 and I want a hard bullet and the formula pops out an answer of 30 BHN, I will be happy. Even if in a lab it will be 31.2334455 BHN.
For our purposes measuring the indentation with a vernier caliper will be accurate enough.
I would also believe the smaller your indenter is, the quicker you will have a result but the more inaccurate your calculated value will be.
Also, since you will only be testing lead, you do not need a carbide ball, just a normal ball bearing should do.
After building, one should take a few test pieces with known hardness and see what you get for a hardness value. In theory this should work perfectly fine for our purposes.
Please see my basic sketch attached
http://www.hardnesstesters.com/image.asbx?AttributeFileId=6f7f900a-6810-48d7-a118-2fd7871d0ce6
http://www.hardnesstesters.com/Applications/Brinell-Hardness-Testing.aspx
Basically you take a hard sphere with a known diameter. Then you place it on the specimen and you apply a load. Then you measure the diameter of the indentation and you plug it into the above formula and calculate the Brinell Hardness.
Now I was thinking, why can one not build one? It should be rather easy. Especially for lead as it is softer than steel. Get a 8mm or whatever ball bearing, get a piece of steel tube with an internal diameter just over 8mm. Secure that in a vertical position. Then, make a ram with a platform where you can place a mass piece.
Put the ball bearing into the tube and hold it with your finger so it does not drop out. Place an ingot under the tube so the ball bearing rests on the ingot. Do not drop the BB into the tube as it will dent the lead, giving you a false reading.
Then slide the ram into the tube (the weight of the ram should be known) and place the weights on the platform. Then leave it for some time (this can be experimentally determined when the indentation stops increasing) and then remove everything and measure the diameter of the indentation on the lead.
Take the weight of the mass pieces in Kilogram and plug that and the diameters into the equation.
In theory you should then have the Brinnel Hardness value for your lead.
Here is another thought. The DIY device will not be as accurate or precise as proper lab equipment, BUT it does not have to be. Firstly you only need a rough figure for harness. It does not matter if it is 10 BHN or 11 BHN.
If I want to cast for my .303 and I want a hard bullet and the formula pops out an answer of 30 BHN, I will be happy. Even if in a lab it will be 31.2334455 BHN.
For our purposes measuring the indentation with a vernier caliper will be accurate enough.
I would also believe the smaller your indenter is, the quicker you will have a result but the more inaccurate your calculated value will be.
Also, since you will only be testing lead, you do not need a carbide ball, just a normal ball bearing should do.
After building, one should take a few test pieces with known hardness and see what you get for a hardness value. In theory this should work perfectly fine for our purposes.
Please see my basic sketch attached