Chipping of tool may occur due to : (a) tool material is too brit

SOLUTION

Explanation:

During any machining process, the tool is subjected to three distinct factors:

forces, temperature and sliding action due to relative motion between tool and work-piece.

Due to these factors, the cutting tool will start giving unsatisfactorily performance after some time.

The unsatisfactory performance may involve:

loss of dimensional accuracy, increased surface roughness, and increased power requirements.

The unsatisfactory performance results from tool wear due to its continued use.

Tool wear or tool failure may be classified as:

• Chipping of the cutting edge
• Flank wear
• Crater wear
• Localised wear such as rounding of cutting edge.

Chipping of cutting edge may occur due to the following factor:

• Tool material is too brittle.
• As a result of a crack that is already in the tool.
• Excess static or shock loading of the tool.
• Weak design of the tool such as a high positive rake angle.

Flank wear is attributed to the following reasons:

• Abrasions by hard particles and inclusions in the work-piece.
• Shearing of micro-welds between the tool and work-piece.
• Abrasions by fragments of built-up edge blowing against the clearance face of the tool

Crater wear usually occurs due to:

• Severe abrasion between chip and tool face.
• High temperature in the chip-tool interface reaching the softening or melting temperature of the tool resulting in an increased rate of wear.

• Crater wear is more common in cutting ductile materials, which produce continuous chips.

  Also, it is more common on the HSS tool than ceramic and carbide tools which have a much higher hot hardness.

The sharp increase in the wear rate after the interface temperature reaches a certain limit is attributed to 'diffusion'.

Diffusion:

It is the movement of atoms between tool and chip material resulting in loss of material from the face of the tool.