Machinability ratings referenced to B1112 steel at 100%, covering carbon and alloy steels, stainless, cast iron, aluminium and superalloys, with the cutting-speed and tool-life consequence of each rating.
Complete reference tables and engineering data for machinability rating. All values verified against ISO, ANSI, and manufacturer standards.
Published starting values are not measurements. They are recommendations, and they differ because each manufacturer optimises for something different — tool life, surface finish, chip control, or spindle power. Two suppliers can quote the same ISO grade and give you cutting speeds 30% apart, and each figure can be right for that supplier’s own geometry, edge preparation and coating.
That is why the number this calculator returns is a starting point, not a setting. Treat the catalogue figure as the middle of a band, then correct it on the first part: if the chips come off blue or the spindle load sits above roughly 80%, come down; if the finish is smeared and the chips are thin and stringy, come up. Write down what actually worked — that shop-specific number beats any published value.
Machinability rating is a relative index comparing how easily a material can be machined. The baseline (100%) is 160 Brinell B1112 free-cutting steel. A rating of 50% means the material machines half as fast with half the tool life; 200% means twice as fast with double the tool life.
304 stainless work-hardens rapidly -- the cutting action itself hardens the material ahead of the tool. The high nickel and chromium content also causes the chip to adhere to the tool (built-up edge), which degrades surface finish and accelerates tool wear. Low thermal conductivity (1/3 of carbon steel) concentrates heat at the tool tip instead of carrying it away with the chip.
Sulphur (0.15-0.35%) and/or lead (0.15-0.35%) additions form inclusions that act as internal chip breakers and lubricants. 12L14 (leaded) and 1215 (non-leaded, high-sulphur) machine beautifully. The trade-offs: leaded steels cannot be welded (hot cracking), and high-sulphur steels have lower transverse ductility and impact strength.
Traditional machinability rating was based on the cutting speed that gives 60-minute tool life with HSS tools. Modern machinability ratings consider multiple factors: tool life, surface finish, chip formation, power consumption, and dimensional stability. The rating is a composite -- a material with 50% rating typically requires 50% of the baseline speed AND gets 50% of the baseline tool life.
Look up your material in this reference to find its machinability rating. Above 100%: use carbide at standard speeds. 50-100%: reduce speeds proportional to the rating. Below 50%: use premium carbide grades (AlTiN-coated, tough substrate), reduce speeds to 30-50% of steel baseline, and expect shorter tool life.
Continue with closely related resources from the machining reference library.
Use the calculator freely. If the result points to a tooling or process problem, we can source the exact carbide tooling you need from vetted factories in China. Compare factory-direct pricing.
Before you commit to a spec, it helps to know what the market pays for it. These are real, publicly listed factory prices — not a quotation, and not a guess.
We source the tool families below direct from vetted Chinese factories, matched to the material and tolerance you just worked out. Every batch ships with its material certificate and dimensional record.
Kennametal grades — KC / KCU / K / KCP series, ANSI C-class mapping, uncoated K313 & K68
Sandvik Coromant grades — GC series, the 43-family hardness ladder, Inveio CVD alumina
Iscar grades — IC prefix, IC9xxx PVD vs IC8xxx CVD, SUMO TEC
Mitsubishi grades — MC / VP / UE / US prefixes and the NX cermet series
Tungaloy grades — T9200 series with published substrate hardness and strength
Seco grades — TP / CP / TS prefixes, Duratomic alumina technology
Walter grades — WPP series, Tiger·tec Gold vs Silver, AlCrN layers
CNMG inserts — Full code decode, real factory price ranges, cutting speeds
Turning insert shapes — WNMG, TNMG, DNMG, SNMG, VNMG, CCMT decoded and compared
Milling inserts — APMT1604, APKT, SEKT decoded; the clearance trap
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Rating a material before you commit to a tool? Our guide covers how to de-risk a new supplier with a sample — measure the diameter and the runout yourself before the order, not after.
We source carbide cutting tools from China for job shops. We do not own a factory, which is why we can quote your drawing against two or three plants that actually run your material.
Cutting formulas with the units worked through · Speed and feed starting points for all six ISO material groups · How to read a carbide grade past its ISO code. 12 pages.
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