The cutting speed for counter-boring should be _________ that of drilling operation.

Answer: Option B

The correct option is "Less than".

Counter-boring is the operation of enlarging the upper portion of an existing drilled hole to make a recess for the head of a bolt or screw.

Since counter-boring involves cutting with a larger diameter tool compared to the original drill, the cutting speed must be kept less than that of drilling. This prevents excessive tool wear, overheating, and ensures accuracy of the recess.

Why not the others?

"Equal to" is incorrect because the larger tool diameter in counter-boring requires a slower speed than drilling.

"Greater than" is incorrect because increasing the speed would cause rapid wear and damage to the counter-boring tool.

"None of these" is incorrect because the correct relationship exists — the speed must be less.

Therefore, the cutting speed for counter-boring should be less than that of drilling operation.