Question

A spindle speed of 300 rpm and a feed of 0.3 mm/revolution are chosen for longitudinal turning operation on an engine lathe. In finishing pass, roughness on the work surface can be reduced by

1. reducing the spindle speed
2. increasing the spindle speed
3. reducing the feed of tool
4. increasing the feed of tool
5.

Answer 1

Correct Answer - Option 3 : reducing the feed of tool

Explanation:

The surface finish in machining operation depends on

1. Type of chip formation
2. Tool profile and geometry
3. Cutting speed

For a tool of finite nose radius r, the peak–to–valley roughness can be evaluated as

\(h = \frac{{{f^2}}}{{8r}}\)

Also \(h = f\tan {\gamma _e} + \frac{r}{2}{\tan ^2}{\gamma _e} - \sqrt {\left( {2fr{{\tan }^3}{\gamma _e}} \right)} \)

From the above equation nose radius, cutting–edge angles and feed rate have an influence on the surface finish.

In turning operation the surface finish can be improved by decreasing feed and increasing nose radius.

Confusion Point: Cutting speed is the most important factor in tool life and not in surface finish.