303 stainless steel bar, also known as UNS S30300 and Grade 303, is considered a free machining stainless steel. 303 stainless steel’s corrosion resistance and great machinability make it one of the most popular free machining stainless steels available. It is used in a wide variety of parts from screw to general machining. Grade 303 does not respond to heat treatment, but the toughness is still excellent as with other austenitic grades.