Pitch of the screw gauge is the linear distance moved in one complete rotation.
Pitch=52.5=0.5 mm
Least count of the screw gauge is given by the ratio of the pitch to the total number of divisions on the circular scale.
Least count=Number of divisions on circular scalePitch
Least count=1000.5=0.005 mm
Least count=5×10−3 mm
Answer: 5×10−3