Engineering Reference

Material group (P/M/K/N/S/H)

The ISO 513 classification of workpiece materials by machining behaviour.

Definition

The six groups let insert grades be selected by behaviour rather than by individual alloy: P steel, M stainless, K cast iron, N non-ferrous, S superalloys and titanium, H hardened materials.

Each group is subdivided by hardness and by whether the material is prone to work hardening or abrasion. The system exists because two alloys with the same hardness can machine very differently — and because it lets a tooling catalogue be organised by a handful of groups instead of thousands of grades.

Common misuse

Selecting an insert grade on hardness alone. Group membership matters as much, particularly for stainless and superalloys.

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