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.

Code

Examples: CNMG 120408, VBMT 160404, CNMG 432, PCLNR 2525M12

Tolerance class Mwhat the class bounds

d: inscribed circle(by size, at ⌀d 12.7 mm); ±0.08 mm
m: corner to the inscribed circle(by size, at ⌀d 12.7 mm); ±0.13 mm
s: thickness; ±0.13 mm

Turning insertCNMG 120408

80° rhombic insert

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

0° clearance

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

M tolerance class

Common pressed class controlling insert size, thickness, and point location, by size: inscribed circle ±0.05 to ±0.15 mm, corner point ±0.08 to ±0.20 mm, thickness ±0.13 mm (ISO 1832 Table 3).

cylindrical fixing hole, chipbreaker both faces

Cylindrical fixing hole; chipbreakers on both faces.

12 mm edge class

Common catalog value: 12.7 mm i.c. Cutting edge l 12.9 mm, between the theoretical sharp corners.

4.76 mm thickness

Common inch-derived insert thickness class.

0.8 mm nose radius

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.