Question

2. Can you offer an explanation as to why the maximum temperature in cutting is located at about the middle of the tool-chip interface? (Hint: Note that there are two principal sources of heat: the shear plane and the tool-chip interface.)

Answer 1

Before coming to the answer of the asked question we need to know about some basics of thermal aspects of metal Cutting.

During metal cutting, the energy dissipated gets converted into Heat.

In fact, heat is generated in two major regions

1. The shear zone-Here the energy needed to shear chip is the source of heat and about 80-85% of heat is generated in this region.
2. The chip-tool interface - Here the energy needed to overcome the friction is the source of heat, about 15-20% of heat is generated in this region.

It will be noted that each of these zones lead to the rise of temperature at the tool chip interface and it is found that the maximum temperature occurs slightly away from the cutting edge i.e. Middle of the tool-chip interface and not at the cutting edge.

The various factors which lead to maximum tool temperature are cutting speed, feed, properties of materials etc. These machining variables affect the size of the shear Zone and chip tool contact length and thereby, the area over which heat is distributed. Shorter length of contact of chip with tool results in severe temperature rise.