Composition, hardness and machinability for 304, 316, 17-4 PH, 420 and the other stainless grades you actually cut, with the cutting-speed consequence of each.
Complete reference tables and engineering data for stainless properties. 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.
Stainless steels span a wide range of machinability -- from free-cutting 303 to difficult-to-machine duplex and precipitation-hardening grades. Selecting the right grade for both performance and manufacturability is essential.
304 has 50% lower thermal conductivity (heat stays at the tool tip), 50% higher work hardening rate (the material gets harder as you cut), high ductility (long stringy chips), and high galling tendency (chips weld to the tool). The combination of work hardening and poor heat transfer makes 304 one of the most challenging materials in terms of tool life per unit of material removed.
Use sharp, AlTiN-coated carbide tools with positive rake angles. Maintain consistent feed (never dwell or rub -- that work-hardens the surface instantly). Use through-tool coolant at correct concentration (8-10%). Keep speeds 30-50% lower than for carbon steel. Climb-mill to minimise work hardening. Avoid re-cutting chips -- ensure good chip evacuation.
303 (austenitic, free-machining) at 78% and 416 (martensitic, free-machining) at 85% are the easiest. Both contain sulphur or selenium additions for chip-breaking. For the best combination of corrosion resistance and machinability, 303 is the standard choice. If hardness is also needed, machine 416 in the annealed condition, then heat treat.
Use this reference to compare stainless steel grades. 303 is the best choice for high-volume machined parts requiring corrosion resistance. 304/316 are the standard general-purpose stainless grades but require careful machining strategy. For the most difficult grades (duplex, PH), use premium carbide tooling and conservative cutting parameters.
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.
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MACHINING STAINLESS? Stainless is where cheap grades fail first, and a substituted substrate shows up as chipping rather than as a complaint about price. See how a supplier's grade claim gets verified.
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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