Question

A vertical boring operation is performed in a cast iron plate to enlarge a blind hole to a diameter of 25 mm up to a depth of 100 mm in a single pass. The cutting speed and the feed used in the process are 100 m/min and 0.1 mm/rev, respectively. Considering the allowance for tool approach as 2 mm, the actual machining time (rounded off to two decimal places) in minutes is ______.

Answer 1

Concept:

Machining time is given as:

\({{{T}}_{{m}}} = \frac{{{{L}} + {{{A}}_{{p}}}}}{{{{f}} {{N}}}}\)

where, T_m = machining time, L = length of the tool travel, A_p = approach length, f = feed, N = speed in rpm.

Calculation:

Given:

Length (L) = 100 mm, Approach length (A_p) = 2 mm, feed (f) = 0.1 mm/rev, Cutting speed (V) = 100 m/min, Diameter (D) = 25 mm

\({{V}} = \;\frac{{{{\pi }}\times {{D}} \times {{N}}}}{{1000}}\)

\(100{\rm{\;}} = {\rm{\;}}\frac{{{\rm{\pi \;}} \times {\rm{25}} \times {\rm{N}}}}{{1000}}\)

N = 1273.239 rpm

Machining time is given by:

\({{{T}}_{{m}}} = \frac{{{{L}} + {{{A}}_{{p}}}}}{{{{f}} {{N}}}}\)

\({{\rm{T}}_{\rm{m}}} = \;\frac{{100 \;+\; 2}}{{0.1\; \times \;1273.239}}\)

∴ T_m = 0.80 minutes.