Brinell Hardness Calculation

[Safeman]

Hi,

I want to make my own Brinell hardness tester. Basically what you do is press a 1 cm steel ball into the surface of a piece of metal to be tested (lead in my case) for 30 seconds under a 100 kg weight. You then measure the diameter of the indentation and apply an equation. The numerator of the equation is in units of Kg (or Kgf). I want to place the ball at the end of a threaded rod and use a torque wrench to push the steel ball into the test piece. Torque is measured in Nm or Lb-ft. How do I convert the torque wrench reading into Kgf? In other words, how many Lb-ft on the wrench will give me the equvialent of a 100 kg weight pressing down on the ball? You may respond here or off forum if you wish to trapdoorspringfield@hotmail.com. Thanks in advance.

[Mike Wright]

In theory it depends on the thread you use, in particular the pitch, but as the friction invoved would be very difficult to predict, and variable, I suspect you would get very inconsistent results. That is why recommended torque values for bolts etc. are only ever given as guidance, because there are too many variables to be precise. I suggest you consider a mass and a lever instead, e.g. 20kg & a lever ratio of 5 =100kg