Machinability rating

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The machinability rating of a material attempts to quantify the differences in machining properties of various materials. Expressed as a percentage or a normalized value. B-1112 steel (160 Brinell AISI B1112 free machining low carbon steel^[1]) is assigned a machinability rating of 100%. A material with a rating of 50% would be roughly twice as difficult to machine and a material with a rating of 200% would be roughly twice as easy to machine. It is apparently based on a subjective weighting of various other machining parameters and can be used as a rough guideline for selecting materials. More detailed information could be obtained by considering the speeds and feeds, surface feet per minute, material removal rate or production Rates, surface finish, machining power, and reject rates.

It is difficult to find information on how the Machinability Rating is calculated.

Machinability is a term that includes several parameters: finish, integrity, tool life, cutting speed, force, chip formation, composition and properties of material etc. In general, tool life and surface finish are measures of machinability. The ratings are given for materials. AISI 1112 steel is given rating of 100. What it means is that, the steel can be machined at 100 fpm for 60 minutes of tool life. [1]

Machinery's Handbook does not have an index entry for machinability ratings, though it does have lots of information on more specific parameters and an entire section on machining econometrics It does have a section on the machinability of wood, using common wood working processes, which is rated based on the percentage of finished parts meeting certain criteria for acceptability.

The American Iron and Steel Institute AISI reportedly (Quaker) tested many alloys to derive Machinability Ratings; however, searching their website does not provide any matches for "machinability ratings" or "machinability index"; the term isn't even listed in their glossary. Ratings are sometimes listed as ASME ratings. ISO is also involved in setting machinability testing procedures, according to the Tool and Manuracturing Engineers Handbook, but searching their web site for machinability yields nothing.

[edit] Links

List of Machinability Ratings from Quaker Chemical taken from Tool and Manufacturing Engineers Handbook, Volume 1 (of 9). Neither tells how they were calculated.
List of Machinability Ratings at Niagara Cutters