why aren’t carbide turning inserts sharp

Why Aren’t Carbide Turning Inserts Sharp?

Introduction:

Cutting tools play a vital role in various industries, with carbide turning inserts being one of the most popular choices. These inserts are renowned for their durability and ability to withstand high temperatures, making them ideal for cutting hard materials like steel and iron. However, despite their reputation, there is a common query that often arises – why aren’t carbide turning inserts sharp? In this article, we will delve into this topic to shed light on the reasons behind this phenomenon.

Understanding Carbide Turning Inserts:

Before we dive into the reasons for carbide turning inserts not being sharp, it’s crucial to have a clear understanding of what these tools are. Carbide turning inserts are cutting tools used in machining to remove material from a workpiece. They are made from a combination of tungsten carbide and a binder metal, such as cobalt. The carbide portion provides hardness and wear resistance, while the binder metal improves toughness.

Reasons for Carbide Turning Inserts Not Being Sharp:

1. Dullness Due to Wear:

As with any cutting tool, wear is an inevitable issue that affects the sharpness of carbide turning inserts. The extreme forces, temperatures, and abrasiveness involved in machining can cause gradual wear on the cutting edges. This wear leads to rounded edges, reducing the inserts’ sharpness and compromising their effectiveness. The severity of wear depends on various factors such as cutting speed, cutting depth, workpiece material, and coolant application.

2. Fracture or Chipping:

Another reason for carbide turning inserts losing their sharpness is fracture or chipping. When the inserts encounter excessive forces or vibrations during the cutting process, they may develop cracks or even break. Such damage not only affects the geometry of the cutting edges but also results in a loss of sharpness. Factors that contribute to this issue include improper cutting parameters, improper tool setup, poor workpiece fixturing, or using inappropriate cutting tools for specific applications.

3. Built-up Edge Formation:

Carbide turning inserts can also lose their sharpness due to built-up edge (BUE) formation. BUE occurs when the workpiece’s material adheres to the cutting edge during machining, gradually increasing its size. Eventually, the built-up edge detaches, leading to the formation of micro-chips, which can cause the cutting edges to become dull and rounded. BUE formation is more common when machining materials with high affinity for the cutting tool, such as aluminum or stainless steel.

4. Improper Cutting Tool Selection:

The choice of carbide turning inserts can significantly impact their sharpness. Different inserts are specifically designed for varying applications, materials, and cutting conditions. Selecting an inappropriate carbide grade, cutting edge geometry, or coating for the desired task can lead to suboptimal sharpness. To optimize sharpness, it is essential to choose the right cutting tool parameters based on the specific machining requirements.

5. Inadequate Cutting Parameters:

The operating conditions during machining, such as cutting speed, feed rate, and depth of cut, can also affect the sharpness of carbide turning inserts. Using inappropriate cutting parameters, such as excessive cutting speed or feed rate, can lead to higher wear rates and reduced sharpness. On the other hand, insufficient cutting parameters may cause rubbing instead of proper cutting action, resulting in the same outcome. Finding the optimal cutting parameters for each machining operation is crucial to maintain the sharpness of carbide turning inserts.

Conclusion:

Carbide turning inserts are popular cutting tools due to their durability and ability to withstand high-temperature machining processes. However, over time, these inserts can lose their sharpness due to wear, fracture, built-up edge formation, improper tool selection, or inadequate cutting parameters. By understanding these reasons, machinists can take appropriate measures to optimize the sharpness and performance of carbide turning inserts. Regular inspection, proper cutting parameters, and selecting the right cutting tool for the job are key to ensuring the longevity and sharpness of these essential tools.