Question

A screw gauge is provided with a “ratchet” arrangement, in the form of a knob at the right end of the spindle. The screw should be rotated by this knob only. The purpose of this device is 

(a) to reduce zero error 

(b) to prevent backlash error 

(c) to control the rate of rotation of the screw 

(d) to prevent damage to the pitch of the screw

Answer 1

Correct Answer is: (d) to prevent damage to the pitch of the screw

The ratchet slips when extra pressure is applied on the screw head at the zero position. This prevents damage to the pitch of the screw.