Q. 64 A hole of 20 mm diameter is to be drilled in a steel block of 40 mm thickness. The
drilling is performed at rotational speed of 400 rpm and feed rate of 0.1 mm/rev.
The required approach and over run of the drill together is equal to the radius of
drill. The drilling time (in minute) is
(A) 1.00
(B) 1.25
(C) 1.50
(D) 1.75
Answer: (B)
Explanation:
