machinability rating

A relative measure of the machinability of a metallic work material under specified standard conditions. Machinability rating is expressed in percents, with the assumption that the machinability rating of AISI 1212 free-machining steel is 100 percent. If machinability ratings of work materials are less than 100 percent, it means that such work materials are more difficult to machine than AISI 1212 steel; and vice versa if machinability ratings are greater than that for AISI 1212 steel.