Question

In a turning operation, the cutting speed is 120 m/min, and the diameter of the workpiece is 50 mm. What is the spindle speed in RPM?

• A. 764 RPM
• B. 382 RPM
• C. 955 RPM
• D. 1910 RPM

Hint:

Ensure units match: convert diameter to meters if cutting speed is in m/s.

Answer 1

The Correct Option is A

Step 1: Recall cutting speed formula
Cutting speed ($V$) = $\frac{\pi D N}{1000}$, where $V$ is in m/min, $D$ is diameter in mm, $N$ is spindle speed in RPM.
Given: $V = 120$ m/min, $D = 50$ mm.
Step 2: Rearrange for N
$N = \frac{V \times 1000}{\pi D}$.
Step 3: Substitute and calculate
$N = \frac{120 \times 1000}{\pi \times 50}$.
$\Rightarrow N = \frac{120000}{157.08} \approx 764$ RPM.