CTR K

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

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 representative Kienzle specific-cutting-force constants and Taylor tool-life defaults for each of the six groups.

Calculators that implement ISO 513

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.
  • Cross-reference with cutting-speed ranges and specific-cutting-force (Kienzle kc1) characteristics typical of each group, providing the quantitative basis for process-parameter calculation.

Governing formulas

Spindle speed from cutting speed (turning/milling/drilling)
n = (1000 · Vc) / (π · D) [rpm]

where n = spindle speed (rpm); Vc = cutting speed (m/min) — chosen from the ISO 513 group range for the selected tool grade; D = workpiece diameter for turning or cutter diameter for milling/drilling (mm). The factor 1000 converts m to mm.

Kienzle specific cutting force (DIN 6584 basis, used per ISO 513 group)
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), characteristic of the ISO 513 material group (P: ~2500, M: ~2200, K: ~1100, N: ~700, S: ~3000, H: ~3500); h = uncut chip thickness (mm); mc = chip-thickness exponent (≈ 0.20–0.27, group-dependent). The Kienzle constants kc1 and mc are the quantitative representation of the ISO 513 material groups in cutting-force calculations.

Taylor tool-life equation (ASME B94.55M, parameters per ISO 513 group)
Vc · T^nT = CT

where Vc = cutting speed (m/min); T = tool life (min); nT = Taylor exponent (dimensionless, typically 0.20–0.35 for carbide grades; harder ISO 513 groups P/S/H tend toward the lower end); CT = Taylor constant (m/min at T = 1 min). The nT and CT constants are selected or calibrated per ISO 513 work-material group and tool-coating combination.

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 speeds and feeds. 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 group defines the range of recommended cutting speeds (Vc) for a given tool grade. P-group steels can generally be turned at 150–350 m/min with modern coated carbides; K-group cast irons at 150–400 m/min; N-group aluminium at 300–800 m/min; S-group super-alloys are limited to 30–80 m/min because of their high heat generation and work-hardening. The subdivision number within each group (e.g. P15 vs P40) further indicates whether a higher Vc (wear-resistant, lower subdivision) or lower Vc (tough grade, higher subdivision) is appropriate for the specific operation.

What is the difference between ISO 513 and ASME B94.55M?

ISO 513 classifies cutting-tool materials and workpiece application groups — it tells you which grade to select and what cutting-speed range to expect. 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 initial cutting-speed range and group assignment; ASME B94.55M provides the tool-life test protocol so the Taylor parameters can be calibrated for a production process.

Is the ISO 513 machining calculator free?

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