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Insert & holder decoder

CNMG 120408 decodes as:C — 80° rhombic shape, N — 0° clearance (negative rake), M — tolerance class, G — geometry with hole and chipbreaker, 12 — 12 mm cutting edge, 04 — 4.76 mm thickness, 08 — 0.8 mm nose radius. Type any ISO 1832 insert designation and this page decodes it field by field; it also reads ISO 5608 turning tool-holder codes (e.g. PCLNR 2525M 12).

Useful mid-quote or mid-FAIR when a process sheet or tooling note names an insert and you need to confirm the nose radius or edge length it implies.

Designation

Examples: CNMG 120408, MCLNR 2525M12

Turning insertCNMG 120408
C

80° rhombic insert

Four-sided diamond insert; size codes are commonly related to inscribed-circle classes.

N

0° clearance

Neutral/negative insert relief; holder geometry supplies working clearance.

M

M tolerance class

Common pressed class controlling insert size, thickness, and point location; typical supplier bands run from about ±0.05 mm on small inserts up to roughly ±0.2 mm on the inscribed circle and corner-point location for larger sizes (ISO 1832 Table 3).

G

cylindrical fixing hole, chipbreaker both faces

Cylindrical fixing hole; chipbreakers on both faces.

12

12 mm edge class

Common catalog value: 12.7 mm i.c.

04

4.76 mm thickness

Common inch-derived insert thickness class.

08

0.8 mm nose radius

DerivedCoverage: common

Derived, own-words encoding of the ISO 1832 / ISO 5608 designation positions — verify against the standards before relying on it for tooling purchases.

ISO 1832 designation system as published in supplier technical guides

Limitation: Covers common indexable turning insert designation positions used in supplier catalogs.

Limitation: Manufacturer chipbreaker suffixes and grade-specific suffixes are intentionally limited.

Values follow the governing standard, which is authoritative for production and inspection decisions. Verify against it before you rely on a number.

Standard names are trademarks of their respective owners; ASdrawn is not affiliated with or endorsed by any standards body.

Metric or inch — which sizes does the code use?

ISO 1832 designations encode dimensions in millimetres; the ANSI B212.4 system used in US catalogs encodes the same physical inserts in eighths and sixteenths of an inch, which is why a CNMG 120408 and a CNMG 432 are the same insert. When a supplier quotes the ANSI number, decode the ISO equivalent and compare the physical dimensions rather than the code text.