Machinability - AISI Rating

Machinability of a material can be defined as the ease with which it can be machined.

Machinability can be expressed as a percentage or a normalized value. The American Iron and Steel Institute (AISI) has determined for AISI No. 1112 carbon steel, a machinability rating of 100%.

http://www.engineeringtoolbox.com/machinability-metals-d_1450.html

http://www.engineeringtoolbox.com/aisi-sae-steel-numbering-system-d_1449.html