Starrett Hardness Test Block - Rockwell Scales
Starrett Hardness Test Blocks can be used to test Rockwell, Brinell, or Vickers scales. They are available in steel, brass, and aluminum. Each block is serialized, with a certificate detailing the environmental conditions used to test the block. Actual readings are given, with the averages of these readings: min. reading, max reading, and a repeatability figure. The blocks are calibrated according to ASTM E-18 standards, ANSI (NCSL) Z540-1, (ISO) 10012-1, ISO/IEC 17025 and Mil-std 45662A.
Starrett hardness test blocks are manufactured from square steel or brass plates, as opposed to the more common round bar stock. The use of the plate gives a more accurate and consistent surface for inspection. Metallurgical tests have proven that during the production of round bar stock, suspended carbides in the mix migrate to the center of the rod. The scientific name for this condition is carbide segregation which results in different readings being found in the center of a rod rather than at its outer edges. Some manufacturers remedy this situation by removing the centers from their blocks.
Hardness test blocks are designed to be used only on one side and the indents should be more than .010in from the centers of two indents or no closer to the block's edge than .040in.