ISO 513 Cutting-Tool Material Classification — Work-Material Groups P, M, K, N, S, H
ISO 513 — Classification and application of hard cutting materials for metal cutting with defined cutting edges — Designation of the main groups and groups of application
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ISO 513 is the international standard that classifies hard cutting materials — cemented carbides, cermets, ceramics, cubic boron nitride (CBN) and polycrystalline diamond (PCD) — into six application groups based on the workpiece material being cut. The six letter-coded main groups are: P (steels), M (stainless steels and high-alloy materials), K (cast irons), N (non-ferrous metals and plastics), S (super-alloys and titanium), and H (hardened steels and chilled cast iron). Each group is further subdivided by a number that indicates the balance between wear resistance and toughness required, guiding the practitioner from a P01 fine-turning carbide grade at the wear-resistant end to a P50 heavy-interrupted-cut grade at the tough end.
The classification is the universal language of cutting-tool catalogues worldwide: every insert grade from every major manufacturer — Sandvik Coromant, Kennametal, Seco, Iscar, Mitsubishi — is mapped to ISO 513 application groups, making the standard the essential bridge between workpiece material, operation type and tooling selection. MechanixCalc's machining calculator uses the ISO 513 group system as its material input for turning, milling and drilling, and ships with one representative Kienzle specific-cutting-force pair (k_c1.1, m_c) and one typical cutting-speed range for each of the six groups. These are the tool's own group-envelope values, not data from ISO 513. Taylor tool-life constants are chosen by tool-material preset (HSS, carbide, cermet, CBN/ceramic), not set per ISO 513 group.
What ISO 513 covers
- Definition and letter-code designation of the six main application groups: P, M, K, N, S, H — each representing a class of workpiece materials that produce similar chip-forming and wear behaviour.
- Subdivision of each main group by number (e.g. P01–P50) to specify the optimal balance between cutting-edge wear resistance and mechanical toughness for the cutting material.
- Coverage of all hard cutting materials with defined cutting edges: cemented carbides (straight WC-Co and coated grades), cermets (TiC/TiN-based), ceramics (Al₂O₃ and Si₃N₄), cubic boron nitride (CBN), and polycrystalline diamond (PCD).
- Assignment of workpiece materials to groups: plain and alloyed steels to P; austenitic and duplex stainless, high-alloy steels to M; grey, nodular and malleable cast irons to K; aluminium alloys, copper alloys and plastics to N; nickel-base and cobalt-base super-alloys, titanium alloys to S; hardened steels (>45 HRC) and chilled cast iron to H.
- Guidance on selecting the application-group subdivision number based on operation type (continuous finish turning at low feeds versus heavy interrupted roughing) and the machining stability.
- NOT in ISO 513: cutting-speed ranges and specific-cutting-force data. ISO 513 is purely a CLASSIFICATION and DESIGNATION standard — it assigns letter/number codes to hard cutting materials and workpiece groups and contains no cutting speeds and no Kienzle k_c1.1 / m_c coefficients. Those come from Kienzle/König test data and manufacturers' catalogues. The MechanixCalc machining tool uses its own typical cutting-speed ranges and group-envelope Kienzle constants, indexed BY the ISO 513 group letter.
Governing formulas
n = (1000 · Vc) / (π · D) [rpm]where n = spindle speed (rpm); Vc = cutting speed (m/min) — chosen within the tool's typical range for the selected group (the tool's own range, not an ISO 513 value); D = workpiece diameter for turning or cutter diameter for milling/drilling (mm). The factor 1000 converts m to mm.
kc = kc1 · h^(−mc) [N/mm²]where kc = specific cutting force at chip thickness h (N/mm²); kc1 = reference specific cutting force at h = 1 mm (N/mm²), the MechanixCalc tool uses one group-envelope value per ISO 513 letter group (P: 2500, M: 2200, K: 1400, N: 1300, S: 3000, H: 4870); h = uncut chip thickness (mm); mc = chip-thickness exponent (0.20–0.27, group-dependent). These are the tool's representative group values, not alloy-specific data and not part of ISO 513.
Vc · T^nT = CTwhere Vc = cutting speed (m/min); T = tool life (min); nT = Taylor exponent (dimensionless); CT = Taylor constant (m/min at T = 1 min). In the MechanixCalc tool nT and CT come from a tool-material preset (e.g. coated carbide n = 0.40, C = 800) that you can edit; they are not adjusted automatically when you change the ISO 513 work-material group, so calibrate them for your tool and workpiece.
Frequently asked questions
What is ISO 513 used for?
ISO 513 classifies hard cutting materials (carbides, cermets, ceramics, CBN, PCD) into six application groups — P (steel), M (stainless), K (cast iron), N (non-ferrous), S (super-alloys), H (hardened) — so that tool catalogues and process engineers share a common language for selecting cutting grades (cutting-speed and feed recommendations come from manufacturers' catalogues, not from ISO 513). Every major tool manufacturer maps its insert grades to the ISO 513 groups, making it the universal reference for tooling selection and CNC process planning.
What are the six ISO 513 material groups?
P covers steels (plain carbon, alloy and tool steels) — long continuous chips, moderate specific cutting force. M covers stainless and high-alloy steels, which are work-hardening and abrasive. K covers cast irons (grey, nodular, malleable) — short chips and abrasive wear. N covers non-ferrous metals (aluminium, copper alloys) and plastics — low forces, high cutting speeds possible. S covers super-alloys (nickel-base, cobalt-base) and titanium alloys — very high heat generation and work-hardening, demanding tough grades. H covers hardened steels (above ~45 HRC) and chilled cast iron — high hardness, very low feeds, wear-resistant grade required.
How does ISO 513 affect cutting speed selection?
ISO 513 itself contains no cutting speeds; it only classifies materials and grades. The MechanixCalc machining tool uses its own typical cutting-speed ranges per group: P steels 150–350 m/min, M stainless 80–200, K cast iron 150–400, N non-ferrous 300–800, S super-alloys 30–80 and H hardened 60–150 m/min. Treat these as starting points and take the final value from your insert manufacturer's catalogue. The subdivision number within each group (e.g. P15 vs P40) indicates the wear-resistance versus toughness balance of the grade.
What is the difference between ISO 513 and ASME B94.55M?
ISO 513 classifies cutting-tool materials and workpiece application groups — it tells you how grades and workpiece groups are designated, not cutting speeds. ASME B94.55M defines the methodology for measuring tool life by the Taylor equation (Vc · T^n = C), so you can empirically determine the Taylor constant and exponent for your specific tool/workpiece combination. In practice the two are complementary: ISO 513 provides the group assignment (the cutting-speed starting range comes from the tool or catalogue); ASME B94.55M provides the tool-life test protocol so the Taylor parameters can be calibrated for a production process.
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