Machinability Index
A comparative rating of how readily a steel can be cut, conventionally set at 100% for free cutting AISI 1212 and expressed as a percentage of it.
Typical ratings
12L14 rates around 160%, EN1A and 11SMn30 at 100%, 1018 near 70%, EN8 at 60%, EN19 and EN24 around 55% annealed, stainless 303 at 78%, 304 at 45% and EN31 near 40% annealed. The figures are a guide to speeds and tool life, not a prediction.
Using it properly
Machinability is not a single number in practice — it trades against surface finish, chip form and tool wear. A grade that cuts fast may leave a poorer finish. Choose on the limiting factor in your cycle: cycle time, tool changes, or finish.
Related terms
Where this applies
Free Cutting Bright Bars, Carbon Steel Bright Bars
Need help applying this?
Stancor Bright Bars engineers answer specification questions directly. Contact us.