Question

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 $cot\alpha$)

• A. $30$% increase
• B. $30$% decrease
• C. $70$% increase
• D. $70$% decrease

Answer 1

The correct option is B $30$% decrease

$\text{Tool life},\text{T}\alpha \frac{\text{1}}{\text{Flank wear}}$

$\text{T}\alpha \frac{1}{\text{cot}\alpha }$

$T\alpha tan\alpha$

$\frac{T_2}{T_1}=\frac{tan{\alpha }_2}{tan{\alpha }_1}=\frac{tan{7}^o}{tan{10}^o}=0.7$

$T_2=0.7T_1$

Tool life decreases by $30\%$.