How Insert Geometry Affects Drilling Performance

Insert geometry, a critical aspect of drill bit design, significantly influences drilling performance. The shape, size, and orientation of the insert are all factors that can affect the efficiency, cost, and overall quality of the drilling process. In this article, we will explore how insert geometry impacts drilling performance, highlighting the various aspects that contribute to this relationship.

Shape and Size of the Insert

The shape of an insert plays a pivotal role in the drilling process. Common shapes include triangular, square, hexagonal, and diamond. Each shape offers different advantages depending on the application:

• Triangular Inserts: These are the most common and versatile shape, suitable for general-purpose drilling. They provide good balance between cutting force and chip evacuation.

• Square Inserts: Square inserts offer increased stability and are ideal for drilling in materials with higher resistance to plastic deformation.

• Hexagonal Inserts: Hexagonal inserts provide excellent stability and are recommended for high-precision and deep-hole drilling applications.

• Diamond Inserts: These inserts are designed for extreme materials, such as carbide, and offer the highest wear resistance but at a higher cost.

The size of the insert is also a critical factor. A larger insert can handle more material removal, but it may lead to increased cutting forces and reduced rigidity, potentially causing deflection or vibration.

Insert Orientation

The orientation of the insert is another important aspect of insert geometry. It affects the cutting edge's geometry and the direction of the cutting forces:

• Positive Rake Angle: This angle, measured from the face of the insert to the cutting edge, helps in reducing friction and increasing chip evacuation.

• Negative Rake Angle: A negative rake angle is used for cutting harder materials, as it reduces the cutting forces and allows for a better finish.

• Positive Relief Angle: This angle, measured from the top of the insert to the cutting edge, helps in reducing edge loading and increasing the tool's life.

• Negative Relief Angle: A negative relief angle is used for cutting soft Indexable Inserts materials, as it provides better chip evacuation and reduces the risk of built-up edge.

Insert Material

The material of the insert also plays a significant role in drilling performance. Common materials include high-speed steel (HSS), cobalt steel, and ceramics. Each material offers different characteristics:

• HSS: Known for its cost-effectiveness and versatility, HSS is Tungsten Carbide Inserts suitable for general-purpose drilling.

• Cobalt Steel: Cobalt steel offers improved hardness and wear resistance, making it suitable for drilling in harder materials.

• Ceramics: Ceramics are the most durable materials for inserts, capable of handling extreme temperatures and abrasive materials.

Conclusion

In conclusion, insert geometry is a crucial factor in determining drilling performance. By selecting the appropriate shape, size, orientation, and material for the insert, manufacturers and operators can achieve better efficiency, cost-effectiveness, and overall quality in the drilling process.