Question

Linked Question
A low carbon steel bar of $147mm$ diameter with a length of $630mm$ is being turned with an uncoated carbide insert. The observed tool lives are $24min$ and $12min$ for cutting velocities of $90m/min$ and $120m/min$ respectively. The feed and depth of cut are $0.2mm/rev$ and $2mm$ respectively. Use the unmachined diameter to calculate the cutting velocity.

Neglect over-travel or approach of the tool. When too life is $20min$, the machining time in min for a single pass is

• A. $5$
• B. $10$
• C. $15$
• D. $20$

Answer 1

The correct option is C $15$

Given data:
$\text{Diameter}=147mm=0.147m$

$\text{Length}=630mm=0.63m$

$Feed=0.2mm/rev=0.2\times {10}^{-3}m/rev$

$\text{Velocity}=97m/min$

$\text{Required time}=\frac{L}{f\times N}$

$\text{and also},V=\pi DNm/min$

$\text{where N is in RPM}$

$\therefore \text{Required time}=\frac{\pi DL}{V\times f}$

$=\frac{\pi \times 0.147\times 0.630}{97\times (0.2\times {10}^{-3})}=14.99=15min$