Understanding insert designation codes can help you identify insert shape, size, geometry, and application more accurately. This guide explains the basic structure of common CNC cutting tool codes and what each letter and number represents.

What Each Part of the Code Means

The table below shows the code structure using two insert designation examples: TNMG160408-TM and CCGT09T304FN-JS. Optional code positions may not appear in every insert designation.

Position	Meaning	TNMG160408-TM	CCGT09T304FN-JS
1	Insert Shape	T	C
2	Relief Angle (Clearance Angle)	N	C
3	Tolerance Class	M	G
4	Hole and Chipbreaker Configuration	G	T
5	Insert Size	16	09
6	Insert Thickness	04	T3
7	Nose Radius	08	04
8(Optional)	Main Cutting Edge Shape	–	F
9(Optional)	Hand / Direction	–	N
10	Chipbreaker Code	TM	JS

Insert Shape Codes

The first letter of an insert designation indicates the insert shape. The shape determines the included angle at the cutting corner and influences cutting-edge strength, accessibility, and machining application.

Shape Code	Insert Shape	Included Angle	Shape Illustration
H	Hexagon	120°
O	Octagon	135°
P	Pentagon	108°
S	Square	90°
T	Triangle	60°
C	Diamond	80°
D	Diamond	55°
E	Diamond	75°
F	Diamond	50°
M	Diamond	86°
V	Diamond	35°
Y	Polygon	25°
W	Trigon	80°
L	Rectangle	90°
A	Parallelogram	85°
B	Parallelogram	82°
K	Parallelogram	55°
R	Round	–

Note: For diamond and parallelogram inserts, the smaller included angle is used as the cutting corner angle.

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Insert Relief Angle Codes

The second letter of an insert designation indicates the relief angle (clearance angle) of the insert. The relief angle affects cutting-edge geometry, cutting forces, and the clearance between the insert and the workpiece.

Relief Angle Code	Relief Angle
A	3°
B	5°
C	7°
D	15°
E	20°
F	25°
G	30°
N	0°
P	11°
O	Other

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Insert Tolerance Class Codes

The third letter of an insert designation indicates the tolerance class. It specifies the dimensional tolerances for the insert corner height, thickness, and inscribed circle diameter.

Tolerance Class	Corner Height (m)	Thickness (s)	Inscribed Circle Diameter (d)
A	±0.005 mm	±0.025 mm	±0.025 mm
F	±0.005 mm	±0.025 mm	±0.013 mm
C	±0.013 mm	±0.025 mm	±0.025 mm
H	±0.013 mm	±0.025 mm	±0.013 mm
E	±0.025 mm	±0.025 mm	±0.025 mm
G	±0.025 mm	±0.13 mm	±0.025 mm
J	±0.005 mm	±0.025 mm	±0.005–±0.13 mm
K	±0.013 mm	±0.025 mm	±0.05–±0.13 mm
L	±0.025 mm	±0.025 mm	±0.05–±0.13 mm
M	±0.08–±0.18 mm	±0.13 mm	±0.05–±0.13 mm
N	±0.08–±0.18 mm	±0.025 mm	±0.05–±0.13 mm
U	±0.13–±0.38 mm	±0.13 mm	±0.08–±0.25 mm

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Insert Hole and Chipbreaker Configuration Codes

The fourth code identifies the insert hole configuration and chipbreaker design, including whether the insert has a hole, the hole shape, and whether the chipbreaker is provided on one or both sides.

Code	Hole	Hole Shape	Chipbreaker	Configuration
N	No hole	–	None
R	No hole	–	Single-sided
F	No hole	–	Double-sided
A	With hole	Cylindrical hole	None
M	With hole	Cylindrical hole	Single-sided
G	With hole	Cylindrical hole	Double-sided
W	With hole	Partially cylindrical, single-sided, 40°–60°	None
T	With hole	Partially cylindrical, single-sided, 40°–60°	Single-sided
Q	With hole	Partially cylindrical, double-sided, 40°–60°	None
U	With hole	Partially cylindrical, double-sided, 40°–60°	Double-sided
B	With hole	Partially cylindrical, single-sided, 70°–90°	None
H	With hole	Partially cylindrical, single-sided, 70°–90°	Single-sided
C	With hole	Partially cylindrical, double-sided, 70°–90°	None
J	With hole	Partially cylindrical, double-sided, 70°–90°	Double-sided
X	–	–	–

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Insert Size Codes

The fifth code indicates the insert size. Depending on the insert shape and designation system, the size code may correspond to the cutting edge length or inscribed circle diameter (IC).

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Insert Thickness Codes

The sixth code indicates the insert thickness. The thickness code corresponds to the nominal insert thickness in millimeters.

Thickness Code	Thickness (mm)
X1	1.39
01	1.59
T1	1.79
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	9.52

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Insert Nose Radius Codes

The seventh code indicates the insert nose radius. The nose radius influences cutting-edge strength, surface finish, and suitable feed conditions.

Nose Radius Code	Nose Radius (mm)
00	0.03
02	0.2
04	0.4
08	0.8
12	1.2
16	1.6
20	2.0
24	2.4
28	2.8
32	3.2

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Main Cutting Edge Shape Codes

The eighth code is optional and indicates the shape or condition of the main cutting edge.

Code	Cutting Edge Type	Shape Illustration
F	Sharp Edge
E	Rounded Edge
W, T	Negative Chamfer
S	Compound Honed Edge

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Insert Hand Codes

The ninth code is optional and indicates the hand or cutting direction of the insert.

Hand Code	Direction	Illustration
R	Right-hand
L	Left-hand
N	Neutral

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Insert Chipbreaker Codes

The tenth code identifies the chipbreaker geometry and its typical machining application. Chipbreaker selection depends on the machining operation, workpiece material, cutting conditions, and insert geometry.

Chipbreaker Code	Typical Application
TM	Semi-finishing; general-purpose selection
HQ	Finishing to semi-finishing
CQ	Finishing to semi-finishing
GS	Semi-finishing to roughing; designed for stainless steel
HA	Light-alloy and stainless-steel machining
HS	Semi-finishing; designed for stainless steel
MQ	Finishing
MA	Medium machining; general-purpose chipbreaker
MS	Medium machining; suitable for stainless steel, mild steel, and difficult-to-machine materials
PM	Semi-finishing
PR	Medium machining

Note: The chipbreaker codes listed above are representative examples. Other chipbreaker codes may also be used depending on the insert series and product specification.

For more detailed chipbreaker selection guidance and recommended cutting ranges, see our CNC Insert Chipbreaker Selection Guide.

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Why Insert Codes Matter

Understanding insert codes helps you select suitable tools, confirm product specifications, and communicate more clearly with tool suppliers and machining partners.

When selecting a CNC insert, understanding the code is only the first step. You also need to consider the workpiece material, machining operation, cutting conditions, and required surface finish.

Consider the Workpiece Material

Different materials require different insert grades and geometries. Consider whether you are machining steel, stainless steel, cast iron, aluminum, or other materials when selecting an insert.

Consider the Machining Operation

The right insert depends on the machining operation, such as roughing, finishing, profiling, threading, or grooving. Choose an insert geometry and chipbreaker suited to the operation and cutting conditions.

Check Cutting Conditions

Cutting speed, feed rate, and depth of cut all affect insert performance and tool life. Make sure the selected insert is suitable for the planned cutting parameters and machine conditions.

Consider the Required Surface Finish

Surface finish requirements can also affect insert selection. Finishing operations may require a suitable insert geometry and cutting edge to achieve the desired surface quality.

If you are unsure which insert to choose, send us your workpiece material, machining operation, and cutting conditions. We can help you review the requirements and identify a suitable option.