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Hardness Testing

Most heat-treated metals have a minimum/maximum Rockwell "C" hardness range. Rockwell hardness testers have ranges from 20 to 80 Rockwell "C" and 0 to 100 Rockwell "B." The Rockwell "C" test uses a diamond tipped indenter with a 150 kg. load. Rockwell "B" uses a 1/16" ball with a 100 kg. load. The deeper the indenter sinks into the metal, the softer the metal is. A Rockwell hardness reading can be converted to an approximate tensile strength (psi) which is very useful when a tensile sample cannot be taken from the item to be tested. There are 20-plus different indenter/load ranges possible depending on the type metal and thickness. Microhardness testers are normally used on a cross-section of metal which has been case hardened to determine the depth of surface hardening. Gears and parts which need to be wear resistant on the surface and soft in the core to resist fracture keep us busy most of the time.

Metal hardness testing
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