Understanding Tool Wear and its Impact on Machining Accuracy

In manufacturing processes like machining, the cutting tool undergoes wear due to friction, heat, and interaction with the workpiece material. Different types of wear occur on the tool surfaces, and each type can affect the machining process in different ways.

Types of Tool Wear

Some common types of tool wear include:

• Flank Wear: This type of wear occurs on the flank face (the clearance face) of the cutting tool. It is caused by friction between the worn flank face and the machined surface of the workpiece.
• Crater Wear: This type of wear occurs on the rake face (the chip flow surface) of the cutting tool, typically some distance behind the cutting edge. It is caused by friction and high temperatures from the chip sliding over the rake face.
• Notch Wear: This wear occurs at the depth of cut line, on both the rake and flank faces, usually at the periphery of the chip. It is often caused by high stress concentration or work hardening of the workpiece material at this point.
• Thermal Wear: This term broadly refers to wear accelerated or caused by high temperatures, which can contribute to other wear types like flank or crater wear, or cause phenomena like thermal cracking.

How Tool Wear Affects Cutting Edge Position and Dimensional Accuracy

The question asks which type of wear affects the position of the cutting edge with respect to the workpiece and alters dimensional accuracy. Let's consider the effect of each relevant wear type:

• Crater wear weakens the cutting edge and can lead to chipping or fracture, but it primarily affects the rake face and doesn't directly change the effective position of the main cutting edge relative to the machined surface as significantly as flank wear.
• Notch wear affects specific areas at the depth-of-cut line and can impact surface finish or cause stress risers on the workpiece, but its primary effect isn't a uniform change in the main cutting edge's position across the width of cut that directly impacts overall dimensional accuracy in the same way as flank wear.
• Flank wear occurs directly below the cutting edge on the clearance face. As flank wear increases, the worn area effectively lowers the position of the cutting edge relative to the ideal cutting plane. This causes the tool to cut less material than intended. For example, in turning, increased flank wear leads to a larger diameter on the workpiece than the programmed size. Therefore, flank wear directly affects the position of the cutting edge relative to the workpiece surface and is a primary cause of loss of dimensional accuracy, often resulting in oversized parts.

Based on this analysis, flank wear is the type of wear that most directly affects the effective position of the cutting edge relative to the workpiece and thus significantly impacts the dimensional accuracy of the machined parts.