Question

What is meant by the pitch of a screw gauge? The pitch of a screw is 1 mm.
Find the reading of the instrument shown in the following figure.

Answer 1

When one complete rotation is given to the screw hand, it moves forward or backward by a distance is called the pitch of the screw. It is a distance between two consecutive threads of the screw.

`"Pitch of the screw" = "distance travelled by screw in n rotations"/"n rotations"`

Pitch of the screw = 1 mm

No. of divisions on circular scale = 100

`"Least count" = "pitch"/"no. of divisions"` = 0.01 mm

Main scale reading = 3 mm

Circular scale division coinciding with the main scale = 42

Circular scale reading = 0.01 x 42 = 0.42

Final reading = 3 + 0.42 = 3.42 mm