Growth of Tool Wear as Function of Time

Q. Cutting tool is much harder than the workpiece. Yet the tool wears out during the tool-work interaction, because

1. extra hardness is imparted to the workpiece due to coolant used
2. oxide layers on the workpiece surface impart extra hardness to it
3. extra hardness is imparted to the workpiece due to severe rate of strain
4. vibration of induced in the machine tool

Q. What is the approximate % change in the life, $t$, of the tool with zero rake angle used in orthogonal cutting when its clearance angle, $\alpha$, is changed from $10$ to $7$ deg?
(Hints: Flank wear rate is proportional to $cot\alpha$)

1. $30$% increase
2. $30$% decrease
3. $70$% increase
4. $70$% decrease

Q. Consider the following statements:
During the third stage of tool wear, rapid deterioration of tool edge takes place because
1. Flank wear is only marginal
2. Flank wear is large
3. Temperature of the tool increases gradually
4. Temperature of the tool increases drastically
Which of the statements given above are correct?

1. $1$ and $3$
2. $2$ and $4$
3. $1$ and $4$
4. $2$ and $3$