The machinability index is relative ease of machining a metal.
American Iron and Steel Institute rated AISI 1212 steel which is equivalent to EN1A in the UK as 100%. This sets a baseline from which you can compare the machinability of different materials.
|AISI 1212 (EN1A)||100%|
|AISI 1040 (EN8)||64%|
Free Machining Steels
A group of steels designated as being easy to machine. Contain one or more additives, which enhance machining characteristics and lower machining cost.