ISO and ANSI code system for Turning Inserts

In the world of CNC machining, turning inserts play a crucial role in shaping and finishing materials with precision. The International Organization for Standardization (ISO) and ANSI (American National Standards Institute) provides ISO and ANSI turning insert nomenclature standards , ensuring consistency and quality across the industry. This classifications includes various notations that describe the key characteristics of turning inserts, such as their shape, relief angle, tolerance, cross-section type, cutting edge length, thickness, nose radius, and chip breaker features. These notations can typically be found in product catalogs, technical data sheets, and online resources provided by tool manufacturers.

Example of ISO Code: Example of ANSI code:

CNMG 120408-HR4 CNMG 432-HR4

• C: Insert shape
• N: Relief or clearance angle
• M: Tolerance
• G: Cross-section type (Mounting style)
• 12 or 4: Cutting edge length / Diameter IC (in mm)
• 04 or 3: Thickness (in mm)
• 08 or 2: Nose radius (in 1/10 mm)
• HR4PM: Chip breaker

Insert Shape

The shape of the turning insert is denoted by the first letter in the ISO/ANSI code. Each shape is designed for specific machining tasks and determines the insert's strength and versatility. Common shapes include:

C (Rhombic, 80°)

• Overview: The most versatile shape for turning applications.
• Advantages: Balanced edge strength and precision, making it an excellent first choice for most operations.
• Ideal For: General-purpose turning, combining strength and versatility.

D (Rhombic, 55°)

• Overview: Used when the 80° C-shape is insufficient for machining complex geometries or achieving fine surface finishes.
• Advantages: More accessible for intricate profiles and tighter angles.
• Ideal For: Semi-finishing and finishing with moderate strength needs.

V (Rhombic, 35°)

• Overview: Optimized for reducing cutting forces during finishing operations.
• Advantages: Best for machining thin walls or long shafts with minimal cutting resistance.
• Ideal For: Precision work and applications requiring reduced forces.

S (Square, 90°)

• Overview: Features the highest edge strength, with four cutting edges (double that of C-shape).
• Advantages: Exceptional durability and robustness under heavy loads.
• Disadvantages: High cutting forces and low versatility.
• Ideal For: Heavy roughing in stable conditions.

T (Triangular, 60°)

• Overview: Compact shape relative to its cutting edge length.
• Advantages: Efficient use of material with a sharp cutting edge.
• Disadvantages: Weaker edge strength compared to other shapes.
• Ideal For: Light turning and applications needing compact tools.

W (Trigon, 80° Equivalent)

• Overview: Similar cutting edge to the C-shape but offers more edges (3 vs. 2).
• Advantages: Increased number of cutting edges for cost efficiency.
• Disadvantages: Shorter cutting edges reduce clamping strength and stability.
• Ideal For: General-purpose turning with a need for more edge options.

R (Round, 360°)

• Overview: The strongest and largest cutting edge of all shapes.
• Advantages: Excellent durability, ideal for handling heavy loads.
• Disadvantages: High cutting forces and limited precision.
• Ideal For: Prolonged roughing operations under heavy conditions.

Relief (Clearance) Angle

The relief angle is indicated by the second letter in the ISO/ANSI code. It defines the angle between the insert's cutting edge and the workpiece, affecting the insert's cutting performance and chip flow. Common relief angles include:

1. (N) Negative Inserts

Inserts with a zero clearance angle (symbol “N”).

Key Features:

• Double-sided inserts, offering double the number of cutting edges.
• Strongest cutting edge for durability under heavy loads.
• Ideal for roughing and general turning operations.
• Advantages:
• Maximized cutting edge strength.
• Cost-effective due to double-sided usability.

Applications:

First choice for roughing and general machining.

2. Positive Inserts

Inserts with any non- zero clearance angle (symbol: “A” = 3°;  “B” = 5°,  “C” = 7°;  “D” = 15°,  “E” = 20°,  “F” = 25°,  “G” = 30°,  “P” = 11°)

Key Features:

• Reduced cutting forces, resulting in lower vibrations during machining.
• Increased clearance between the insert and the workpiece.
• Suitable for machining smaller internal diameters during boring operations.
• A greater positive rake angle underline these benefits but decreases edge strength.

Advantages:

• Lower cutting forces, which improve surface finish and reduce wear on tools and machines.
• Superior performance in delicate operations, such as fine finishing or machining thin-walled components.

Applications:

• First choice for finishing operations (both internal and external).
• Essential for internal turning inside small-diameter holes.

Tolerance

Tolerance is represented by the third letter in the ISO code and specifies the allowable deviation from the nominal dimensions of the insert. Tighter tolerances ensure higher precision and better surface finishes. Common tolerances include:

The all specify the following allowances:

• Tolerance of d (IC)
• Tolerance of m (Edge Position)
• Tolerance of s (Thickness)

Cross-Section Type (Mounting Style)

The cross-section type is indicated by the fourth letter in the ISO/ANSI codes and simultaneously describes two non directly connected parameters of the insert: 1. Mounting Method: Describes how the insert is clamped onto the toolholder and 2. Chipbreaker: Indicates the presence and position of the chipbreaker on the insert. It does not define the geometry of chip breaker , though.

Code - Chipbreaker Placement - Insert Type

• G - Both sides - Round flat center hole
• M -Top side only - Round flat center hole
• A - No chipbreaker - Round flat center hole
• T - Top side only - Round center hole, 40°-60° chamfer on top
• W - No chipbreaker -Round center hole, 40°-60° chamfer on top
• U - Top side only - Round center hole, 40°-60° chamfer on top & bottom
• Q - No chipbreaker - Round center hole, 40°-60° chamfer on top & bottom
• H - Top side only - Round center hole, 70°-90° chamfer on top
• B - No chipbreaker - Round center hole, 70°-90° chamfer on top
• J - Top side only - Round center hole, 70°-90° chamfer on top & bottom
• C - No chipbreaker - Round center hole, 70°-90° chamfer on top & bottom
• F - Both sides - No center hole
• R - Top side only -No center hole
• N - No chipbreaker -No center hole

Cutting Edge Length / Diameter IC

The cutting edge length (ISO) or diameter IC (ANSI) is represented by a number following the cross-section type. This measurement indicates the size of the insert and is crucial for ensuring compatibility with the tool holder and the workpiece. For example:

In our example – 12 / 4: Indicates a 12mm cutting edge length /or 12.7 diameter IC.

Thickness

The thickness of the turning insert is denoted by a two-digit number following the cutting edge length. This measurement, in millimeters, affects the insert's durability and ability to withstand cutting forces. For example:

In our example – 04 / 3: Indicates a thickness of 4.76mm / 0.1875”.

Nose Radius

The nose radius is indicated by a number following the thickness. This measurement defines the radius of the insert's tip and influences the surface finish and cutting stability. For example:

In our example – 08 / 2 : Indicates a nose radius of 0.8mm / 0.0313“.

Chip Breaker

The chip breaker is represented by additional letters or symbols at the end of the code. It describes the design features that help break the chips into manageable pieces, improving chip control and reducing heat buildup during machining. Each manufacturer develops their own chip breakes and their codes, but chip breaker designs can be specified as:

• For medium cutting, providing a balance between chip control and cutting forces.
• For finishing, designed to produce fine chips and a smooth surface finish.
• For roughing, designed to handle heavy cutting forces and produce larger chips.

In summary, understanding of turning insert codes allows machinists to select the appropriate insert for their specific machining needs. By considering the insert's shape, relief angle, tolerance, cross-section type, cutting edge length, thickness, nose radius, and chip breaker features, machinists can achieve optimal performance, precision, and efficiency in their operations.