Welding Inspection & Metallurgy API ICP Self Study Notes

The Rockwell test is simple and rapid. The minor load is automatically applied
by manually bringing the work piece up against the indenter until the “set”
position is established. The zero position is then set on the dial gage of the
testing machine. The major load is then applied, and without removing
the work piece, the major load is removed, and the Rockwell number then
read from the dial.
In Rockwell testing, the minor load is always 10 kg, but the major load can be
60, 100 or 150 kg. Indenters can be diamond cone indenters (commonly
known as Brales), or hardened steel ball indenters of various diameters. The
type of indenters and applied loads depends on the type of material to be
tested. A letter has been assigned to each combination of load and indenter.
Scale is indicated by a suffix combination of H for Hardness, R for Rockwell
and then a letter indicating scale employed. For instance, a value of 55 on the
C scale is expressed as 55 HRC.