How to convert torque (Nm) to KGf

Questions and answers on how to convert things from one unit or system to another


How to convert torque (Nm) to KGf

Postby Safeman » Tue Dec 20, 2005 11:40 pm

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 Thanks in advance.

Converting torque to pressure

Postby Jens » Sat Dec 31, 2005 5:52 am

The question you ask does not have as simple an answer as you may wish. The problem is they are dependent upon a conversion ratio of your apparatus. For example, in most rear wheel cars the power output to the wheels is not a 1:1 ratio with that of the transmission output. The power is converted at the rear end (however slightly) depending on the gear ratios therein. In your situation you would have to calibrate your apparatus or calculate the conversion yourself. This could be done by either testing materials of known value, then calculating the factor or if you can get a measurement device (fairly accurate scale) and then measure the torque you have to apply to get the 100kg of downward force. A bathroom scale is NOT even remotely accurate so do not use it to get the measurements. You may have to rent a scientific scale of find a calibration laboratory that would do the conversion for you. Note that any change in temperature and/or lubrication could seriously affect the accuracy of your device.


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