Question

If cutting tool travel 1000 mm in the direction of feed motion with work piece rotational speed of 500 rpm and feed rate of 0.2 mm/rev, machining time in minutes will be:
1. 6
2. 10
3. 2
4. 8

Answer 1

Correct Answer - Option 2 : 10

Concept:

Machining Time in Lathe:

Let a steel rod be reduced in diameter from D1 to D2 over a length Lw by straight turning in a centre lathe. 

The machining time Tc (min) is given by –

\({T_c} = \frac{{{L_c}}}{{{s_o}N}}\)

where N = spindle speed (rpm), so = feed of tool (mm/rev)

Lc = actual length of cut = Lc = Lw + A + O

here A = approach, O = over-run and Lw = length of turning done on material.

[Note: When approach and over-run is not mentioned take it as zero]

Calculation:

Given:

L_w = 1000 mm, N = 500 rpm, s_o = 0.2 mm/rev.

Lc = Lw as approach or over-run is zero.

\({T_c} = \frac{{{L_c}}}{{{s_o}N}} \)

\({T_c} = \frac{{{1000}}}{{{0.2\;\times\;}500}} =10\;min\)