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Machining

ISO 1832 insert designation

In short

Read CNMG 120408: shape, clearance, tolerance, fixing, size, thickness, radius.

Example: turning insert

CNMG120408

CShape: 80° rhombic
N0° clearance: negative insert, usable on both faces
MTolerance M: d ± 0.05 to 0.15 mm
GCylindrical hole, chip breakers on both faces
1212 mm cutting edge (12.7 inscribed circle)
04Thickness 4.76 mm
08Nose radius 0.8 mm

The first seven symbols are compulsory. Sometimes followed by ⑧ edge condition and ⑨ hand (R right, L left), then the maker’s chip breaker and grade.

① Shape

Letter	Shape	Angle (°)
C	Rhombic	80
D	Rhombic	55
E	Rhombic	75
M	Rhombic	86
V	Rhombic	35
S	Square	90
T	Triangular	60
W	Trigon	80
P	Pentagonal	108
H	Hexagonal	120
O	Octagonal	135
L	Rectangular	90
A	Parallelogram	85
B	Parallelogram	82
K	Parallelogram	55
R	Round	—

② Clearance

Letter	Angle (°)
N	0
A	3
B	5
C	7
P	11
D	15
E	20
F	25
G	30

N: negative insert. Other letters: positive inserts, one usable face.

③ Tolerance (± mm)

Class	d circle	m corner	s thickness
C	0.025	0.013	0.025
E	0.025	0.025	0.025
G	0.025	0.025	0.13
H	0.013	0.013	0.025
M	0.05to 0.15	0.08to 0.2	0.13
U	0.08to 0.25	0.13to 0.38	0.13

M and U: the deviation depends on the insert size.

④ Fixing and chip breakers

NNo hole, no chip breaker
RNo hole, chip breaker on one face
ACylindrical hole, no chip breaker
MCylindrical hole, chip breaker on one face
GCylindrical hole, chip breakers on both faces
W40 to 60° countersunk hole one side, no chip breaker
T40 to 60° countersunk hole one side, chip breaker on one face

⑤ Edge length by shape

Circle (mm)	C	D	T	V	W
6.351/4″	06	07	11	11	04
9.5253/8″	09	11	16	16	06
12.71/2″	12	15	22	22	08
15.8755/8″	16	19	27	27	10
19.053/4″	19	23	33	33	13
25.41″	25	31	44	44	17

Square S: the symbol is the inscribed circle (12.7 → 12). Round R: its diameter.

⑥ Thickness

Symbol	Thickness (mm)
01	1.59
T1	1.98
02	2.38
T2	2.78
03	3.18
T3	3.97
04	4.76
05	5.56
06	6.35
07	7.94
09	9.53

⑦ Nose radius

Symbol	Radius (mm)
00	Sharp
02	0.2
04	0.4
05	0.5
08	0.8
12	1.2
16	1.6
20	2.0
24	2.4
32	3.2

The symbol is the radius × 10.

Sources

ISO 1832:2017 : désignation des plaquettes amovibles : Art. 4, tableaux 1, 2, 3 et 6 (extrait public iTeh) (link)
Ingersoll MAN-037-1 : turning insert nomenclature ANSI / ISO : Longueur d’arête, épaisseur, rayon de bec, sens (link)

Updated 9 November 2026 · Publisher: The Level Code

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