The least count of a screw gauge can be decreased by:
Decreasing the pitch of the screw gauge.
Increasing the total number of divisions on its circular scale.
Least count of a screw gauge = Pitch of the screw gaugeTotal number of divisions on its circular scale.
Therefore, the least count of a screw gauge can be decreased by decreasing the pitch of the screw gauge and increasing the total number of divisions on its circular scale.