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Scale Units for Rockwell N (Rn) Hardness Scale

Scale Units for Rockwell N (Rn) Hardness Scale

The Rockwell N Scale is primarily used for comparing case hardened metals and hard thin sheet metals. Although there are several N tests we will use the 15 kg load example for comparison. A conical diamond (Brale) is forced into a test specimen with a 40 kg minor load and then a 15 kg major load is applied. The major load is removed and the Rn number value is given by dial or digital readout. This chart compares the Rn values to Rockwell C values.

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