Question

3. As a tool experiences crater wear, in general, the deepest point in the crater
formed on the tool rake face occurs at a distance away from the tool tip,
rather than at the tool tip. Elucidate the physics behind this observation.

Answer 1

During machining when the upward force is acting by tip of the tool onto the layer of work material, the chip produced will be lifted upwards directly but because of presence of self weight of chip, it is falling back on to the rake face of the tool. During the process of lifting upwards and falling back, there is no contact present between chip and tool near the tip of the tool. When there is no contact is present no friction, no abrasive action, and no diffusion will takes place near the tip of the tool.

When the chip is falling back onto the rake face of the tool, it is trying to penetrate into the tool at some distance away from the tip. At this point, the friction is high, heat generation is high and hence, the temperature.