Correct option is A
The faces of slip gauges are finished by lapping only. Slip gauges are precision measuring tools used to calibrate and check instruments and machine parts.
They are manufactured with extremely high accuracy and require a very fine surface finish for proper use and adherence. These slip gauges are available in various sets with different numbers.
Lapping is a precision finishing process that involves rubbing two surfaces together with an abrasive to achieve an ultra-smooth and flat surface.
It is commonly used for finishing the measuring faces of slip gauges to achieve the required flatness and accuracy.
