Tool deterioration occurs through aging, sudden impacts such as breakage, and chemical interactions between the workpiece and the cutting material. Here, we explain wear on tools during the cutting process and introduce countermeasures. Wear or chipping on the tool edge not only reduces machining accuracy and speed but also can deform or damage the workpiece and cause machine failure. Therefore, observing and understanding the condition of the cutting edge directly relates to the capability of the cutting process.
There are types of tool wear, caused by factors such as heat load from friction, vibration, and contact with chips or wear particles (wear dust). Tool damage during machining is broadly divided into wear type and breakage type.
Phenomena classified under breakage type include chipping and breakage, and typical phenomena classified under wear type include the following:
A wear phenomenon where small indentations form at the tip of the tool, making the area around the indentation step-like. It mainly occurs under high-speed rotation or high load, caused by the cutting edge sliding against the cutting material. Continuing to machine in a state of crater wear can lead to chipping, welding, and breakage of the edge.
A wear phenomenon that occurs on the side of the tool, characterized by linear scratches running horizontally across the tool surface. It mainly occurs under poor machining conditions or when the workpiece is of high hardness.
A wear phenomenon that occurs at the boundary between the tip and the side of the tool, characterized by the rounding of the cutting edge's tip. It mainly occurs under poor machining conditions or when the workpiece has high viscosity.
For each type of wear mentioned above, there are corresponding countermeasures as follows:
Crater wear often occurs on the tool's rake face. The primary countermeasures include revising cutting conditions such as cutting speed and feed rate. Additionally, reviewing the use of tools and work materials, as well as utilizing cutting fluids to achieve cooling and lubrication effects, can be effective.
Wear occurring on the flank face is referred to as flank wear. It requires setting appropriate machining conditions and using cutting fluids with cooling effects. Flank wear is caused by the frictional heat applied to the cutting edge, leading to its overheating. Thus, setting appropriate cutting conditions to prevent excessive frictional heat is crucial. Among these, setting the correct machine angle and adjusting the machining angle with the tool can prevent flank wear.
Boundary wear occurs when the edge of the cutting edge catches and scrapes or splits the work material. It is especially likely to happen when using inexpensive tools that are not scooped. In addition to reviewing tools, adjusting chip evacuation methods and increasing the cutting edge angle to improve sharpness and reduce cutting resistance can be effective.
Tool wear in machining is an inevitable issue, but by taking appropriate measures, its impact can be minimized. Machinists should understand how to deal with different types of wear and implement appropriate measures to extend tool life and improve manufacturing productivity.
