Classification, Key Parameters, Common Groove Types and Effect Evaluation of Chip Breakers

With the development of indexable tool technology and powder metallurgy technology, the groove types and functions of chip breakers have become increasingly complex and diverse. In addition to traditional basic groove types such as straight grooves, inclined grooves, and curved edges, various groove types with protrusions, pits, and curved surfaces have emerged. Today, we will learn about the relevant knowledge of chip breakers.

History of Chip Breaker Development

The historical development stages of chip breaker groove types can be summarized into four phases: the crater-type chip breaker stage, the obstacle-type chip breaker stage, the chip breaking direction research stage, and the 3D chip breaker stage, as shown in the figure below.

Classification of Chip Breaker Groove Types

Traditional chip breakers can be divided into three types: straight type, circular arc type, and straight-circular arc type, with their structural schematics shown in the figure below.

The chip breaking effect can be measured to a certain extent by the chip curl radius. Specifically, the smaller the curvature of the chip breaker groove, the smaller the chip curl radius, the greater the chip deformation, and the easier the chip is to break.

The straight-circular arc type chip breaker consists of a straight section connected to a circular arc section. The straight section guides chip evacuation, while the subsequent circular arc section causes the chip to curl, thereby inducing deformation and fracture. The smaller the diameter of the circular arc section, the easier the chip is to break.

The straight-type chip breaker is formed by the intersection of two straight sections, and its groove bottom angle is the supplement of the wedge angle of the chip breaking land.

In the model shown in Figure b, the groove bottom angle replaces the role of the groove bottom arc radius R in the two models (Figures a and c). Specifically, the chip will come into contact with the rear groove surface before reaching the intersection of the two straight sections; upon contact, the chip curls and deforms directly. At this point, the smaller the groove bottom angle, the smaller the chip curvature and curl radius, and the easier the chip is to break.

Compared with the previous two types, the circular arc-type chip breaker has a relatively larger rake angle. An increase in the rake angle means a smaller chip curl radius and greater chip deformation, making the chip easier to break. Therefore, it is mostly used for cutting high-plasticity materials such as red copper.

Additionally, due to its full circular arc structure, the groove depth is relatively small, ensuring smoother chip flow and better practicality in engineering applications.

Analysis of Chip Breaker Parameters

The basic structural diagram of the chip breaker groove type is shown in the figure below.

This paper takes the straight-circular arc type chip breaker as an example to illustrate the influence of its geometric parameters on chip breaking performance.

In the figure above:

• b_r: Width of the negative land;
• W_n: Normal groove width of the chip breaker on the main cutting edge (abbreviated as groove width);
• γ₀: Rake angle of the chip breaker tool (abbreviated as rake angle);
• γ₁: Rake angle of the negative land;
• h: Cutting edge height;
• H: Depth of the chip breaker (abbreviated as groove depth).

Changes in each parameter directly affect the groove type and chip breaking performance of the chip breaker. Based on a comprehensive review of literature, the following conclusions are drawn:

1. Negative land: Enhances the strength of the tool tip; the width must be optimized—excessively wide increases cutting force, while excessively narrow reduces tool life.
2. Rake angle: A larger rake angle leads to greater chip deformation, a smaller curl radius, and easier chip breaking.
3. Groove width/groove depth: These two parameters are interrelated in affecting chip breaking, with their ratio used as a design parameter. Wide grooves are suitable for rough machining, and narrow grooves for finish machining; the groove depth is set to a smaller value relative to the groove width (excessively wide grooves hinder chip breaking, while excessively narrow ones easily cause chip clogging).
4. Cutting edge height: Constrained by groove depth. For the same groove depth: reducing the height increases the rake angle, decreases chip deformation/cutting force (making chip breaking difficult), and reduces edge strength; increasing the height strengthens the resistance of the groove back to chips, facilitating chip breaking.
5. Chip reversing angle: A larger angle promotes easier chip breaking.
6. Lead angle: Increasing the lead angle results in narrower and thicker chips, improving chip breaking performance.
7. Inclination angle: Affects chip flow direction (a positive angle directs chips to the workpiece to be machined, suitable for finish machining; a negative angle directs chips to the machined surface, affecting surface quality). It is usually set between 5° and 15°.

Classic Groove Types and Their Characteristics

This paper selects cemented carbide tools (with a clearance angle of 0°) from 8 enterprises with high market share (Mitsubishi, Kyocera, Sumitomo, Daido, Sandvik, Korloy, Taegutec, and Walter). Based on geometric shape classification, 9 types of basic groove types and their design characteristics are summarized, as shown in the table below.

Among the 9 types of basic groove types listed in the table above, 4 groove structures have been improved based on previous designs to achieve better chip breaking performance. The structures of these 4 typical groove types are shown in the figures below, with a classic case cited for each type:

Figure a: Straight-circular arc double-groove type (with convex elastic retainer on the groove back). Its feed rate is higher than that of rigid retainers; the chip contact area is small, the curl radius is small, and the convex surface enhances lateral curling, resulting in superior chip breaking performance.

Figure b: Double-circular arc structure (with small convex elastic retainer at the end of the groove back, and rake angle decreasing from front to rear). The small rake angle increases chip deformation, and the front circular arc already facilitates chip breaking, so no large convex retainer is needed to achieve the desired effect.

Figure c: Straight flat-bottom type. It overcomes the stress concentration issue of traditional sharp-bottom structures and improves tool tip strength; a larger rake angle can be set to reduce cutting force and temperature, making it suitable for cutting plastic materials.

Figure d: Double straight-groove type. The two grooves are respectively adapted for finish/rough machining (the first deep groove breaks chips during finish machining, and the second groove during rough machining), enabling compatibility with multiple machining scenarios.

In addition, traditional groove types can be further optimized (e.g., curved/wavy edges, convex chip reversing surfaces, friction-reducing structures, etc.) to enhance manufacturability and adaptability.

Two typical specially designed chip breaker groove types are presented in this paper, as shown in the figures below.

Evaluation of Chip Breaking Effect

The chip curl radius is a universal criterion for measuring chip breaking performance.

Chip curling occurs in two forms: two-dimensional (2D) curling and three-dimensional (3D) curling. Among these, 2D curling mainly includes upward curling and lateral curling, and extensive research has been conducted on the theory of 2D upward curling to date.

For example, predictions have been made on the chip curl radius of straight-type and straight-circular arc-type chip breakers. The schematic diagram of chip curling for the straight-type groove is shown in the figure below:

The schematic diagram of chip curling for the convex surface groove type is shown in the left figure below, and that for the straight-circular arc type groove is shown in the right figure below.

After comparing the empirical formulas summarized by previous researchers, the following conclusion is drawn: The chip curl radius is proportional to the groove width and inversely proportional to the rake angle—namely, a smaller groove width and a larger rake angle are conducive to chip breaking.

Conclusion

This paper systematically collates the relevant knowledge of chip breakers, covering their development history (four stages), traditional classifications (straight type, circular arc type, straight-circular arc type), and core chip breaking principle (direct correlation between groove curvature, chip curl radius, and chip breaking effect).

It elaborates on the influence laws of key geometric parameters (such as negative land, rake angle, and groove width/groove depth) on chip breaking performance, and introduces typical optimized groove types (e.g., straight-circular arc double-groove type, double-circular arc structure) as well as special design directions (e.g., curved edges, convex chip reversing surfaces).

Finally, it confirms that the chip curl radius is a universal criterion for evaluating chip breaking effect, and that a smaller groove width and a larger rake angle are more conducive to chip breaking. This paper comprehensively presents the technical development and design logic of chip breakers.