Tool Wear: Types, Factor Affecting, Causes and Remedies

Hello, friends today we are going to talk about tool wear in which you will learn what is tool wear, types of tool wear as well as their causes and remedies.

In General, Tool Wear Signifies the Erosion of Material from the Surface.

Wear, in this context, denotes the diminishing volume and geometric characteristics of the tool. It encapsulates the deterioration experienced by cutting tools over continuous operation.

Should a tool fall short of delivering satisfactory performance, it serves as a clear indication of tool failure.

What is Tool Wear?

Tool wear refers to the gradual loss or deterioration of material from the surface of a cutting tool during its use. It is a natural and unavoidable phenomenon that occurs due to the friction and heat generated during the cutting process. As a tool repeatedly comes into contact with the workpiece, the material on its surface undergoes wear, leading to changes in its volume and geometric properties. Tool wear can impact the tool’s performance, affecting the quality of the machined workpiece and necessitating the need for tool replacement or reconditioning.

Tool wear depends upon the following parameters:
  1. Tool and workpiece material.
  2. Tool shape
  3. Cutting Speed
  4. Feed and Depth of cut
  5. Cutting fluid used.
  6. Machine Tool characteristics, etc.

What happens If Tool Wear Occurred?

When tool failure occurs, several drawbacks become evident:

  1. Inability to produce workpieces according to the required dimensions.
  2. Overheating of the tools.
  3. Excessive surface roughness in the machined workpiece.
  4. Increased cutting forces leading to higher power requirements.
  5. Potential for tool breakdown.
  6. Reduced accuracy of the tool product and decreased tool life.

Types of Tool Wear

The failure of the cutting tool can be divided into two categories according to the failure mechanism of the cutting tool:
  • Slow-Death Mechanism
  • Sudden-Death Mechanism

Slow-Death Mechanism

In the slow-death mechanism, Gradual tool wear occurred on the flank of the tool (or) on the rake face of the tool(crater wear) or nose on the tool. 

Types of Gradual Tool Wear

Gradual tool wear can be classified into the following types:
  • Flank Wear
  • Crater Wear
  • Nose Wear
  • Notch Wear
See in the figure types of tool wear which are described below in detail.
Tool Wear Types, Factor Affecting, Causes and Remedies
Tool Wear Types, Factor Affecting, Causes and Remedies

 

Flank Wear

Flank wear is a wear type that manifests on the flank face (relief or clearance face) beneath the cutting edge of the tool.

It arises due to abrasion between the tool flank and the freshly machined workpiece surface.

Flank wear tends to be more pronounced near the tool’s nose and is not uniform along the cutting edge.

Typically, it is a consequence of elevated temperatures impacting both the tool and the workpiece.

This form of wear is prevalent on all tools employed for cutting various work materials.

Reasons for Flank Wear 

  1. Flank wear increases rapidly with increasing cutting speed and increases in feed and depth of cut can also result in larger flank wear. 
  2. Abrasion by hard panicles in the workpiece. 
  3. Shearing of micro welds between tool and workpiece. 
  4. Abrasion by fragments of built-up edge, which strike against the flank face of the tool.

Remedies for Flank Wear 

  1. Reduce cutting speed, feed, and depth of cut. 
  2. Use the hard grade of carbide & prevent the formation of built-up breakers.

Crater Wear

Crater wear refers to the wear on the rake face of the tool.

During crater wear, the rake face of the tool is eroded by chips.

Chips flowing across the rake face generate significant friction between the chip and the rake face.

It doesn’t impair the tool’s usability until it leads to cutting-edge failure.

While crater wear can increase the working rake angle and reduce cutting force, it simultaneously compromises the cutting edge’s strength.

This phenomenon is more prevalent in ductile materials like steel, which produce continuous chips over extended periods.

Crater wear is more commonly observed in High-Speed Steel (H.S.S.) tools than in carbide tools due to the latter’s higher hot hardness.

The depth of the crater is a widely used parameter for evaluating rake face wear.

It occurs at a height equivalent to the cutting depth of the material, particularly in high-temperature zones, around 700°C.

Reasons for Crater Wear 

Severe abrasion occurs between chip-tool interfaces, particularly on the rake face.

Elevated temperatures are experienced in the tool-chip interface.

An escalation in feed rate contributes to a rise in the temperature of the tool-chip interface.

Similarly, an increase in cutting speed leads to higher chip velocity at the rake face, subsequently raising the temperature at the chip-tool interface and consequently intensifying crater wear.

Remedies for Crater Wear 

Severe abrasion occurs between chip-tool interfaces, particularly on the rake face.

Elevated temperatures are experienced in the tool-chip interface.

An escalation in feed rate contributes to a rise in the temperature of the tool-chip interface.

Similarly, an increase in cutting speed leads to higher chip velocity at the rake face, subsequently raising the temperature at the chip-tool interface and consequently intensifying crater wear.

Nose Wear

Nose wear arises due to abrasion between the nose and the machined metal.

It is categorized as part of flank wear, with no distinct boundary separating them.

It is alternatively referred to as corner wear.

Notch Wear

Notch wear predominantly involves oxidation wear on the trailing edge, where the cutting edge releases material from the machined workpiece in the feed direction.

This wear occurs when the tool rubs against the original work surface, which is harder than the machined material.

Reasons for Occurred Gradual Tool Wear

These types of tool wear mechanisms are occurred due to the following reasons:
  • Abrasion
  • Adhesion 
  • Diffusion 
  • Chemical interactions
  • Oxidation

Abrasion Wear

Abrasion wear occurs due to mechanical abrasion between the workpiece material and the cutting tool.

In this type of wear, hard particles on the underside of the chip pass over the tool face.

Adhesion Wear

As part of the friction mechanism, junctions are formed between the chip and the tool material.

When these junctions fracture, small fragments of the tool material can be torn out and moved under the chip or to the new workpiece surface.

Diffusion Wear

This type of wear occurs due to the diffusion process, where atoms in a metallic crystal lattice move from a region of high atomic concentration to a region of low concentration.

During metal cutting, when the temperature is high at the interface of the tool and workpiece, the atoms move from the tool material to the workpiece material, thereby weakening the structure of the tool.

Chemical Interaction

This occurs due to the chemical affinity between the workpiece material and the cutting tool material.

Oxidation

Oxidation results from a chemical reaction between the tool face and oxygen.

Sudden-Death Mechanisms

In the sudden death mechanism, tools experience rapid, usually unpredictable, and often catastrophic failures, leading to the abrupt and premature termination of the tool’s functionality.

Read also: Are PET Bottles Safe for us and the environment?

Sudden-death mechanisms are straight forward but less predictable. 
These mechanisms are categorised as:
  • Plastic Deformation 
  • Edge Chipping
  • Fatigue Fracture 
  • Brittle Fracture  

Plastic Deformation

It occurs due to a loss of hardness occurring at the cutting point.

The combined effect of cutting force and cutting temperature induces deformation in the tool.

Edge Chipping

This tool failure results from an excessive chip load, compounded by the inability of the coolant to consistently cover the cutting point.

Fatigue Fracture 

Fatigue fracture occurs due to the expansion and coalescence of cracks, and with an increase in the feed rate, the predominant failure mode of the tool is fatigue fracture.

Read also: Types of Cutting Tool Materials and Their Properties

Brittle Fracture  

Brittle fracture occurs when stress surpasses cohesion and takes place under yield stress, typically happening at lower stress levels.

Now, you have gained knowledge about the types of tool wear, factors influencing tool wear, and their causes and remedies. If you have any questions, feel free to reach out through email or our contact us page.

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