Question

Draw a neat labeled diagram of a screw gauge. Name its main parts and state their functions.

Answer 1

Hint :Screw gauge is an instrument which is used for measuring dimensions of small objects like the radius of a tiny sphere or radius of a thin wire etc. It can measure with an accuracy of $0.01mm$ or $0.005mm$ for some Screw Gauges that are available in the market.

Complete Step By Step Answer:
We know, Screw Gauge is a mechanical tool which facilitates measuring diameter or radius or thickness of thin wire or of metal sheets with accuracy.

 Upon one rotation of the screw moves the base line a distance equal to the pitch of the screw. The measurements are done through a screw of a pitch of $0.5mm$ , that means on completion of one revolution of the circular scale the displacement of the baseline is $0.5mm$ .
Main parts and their functions of a Screw gauge are given below:
Ratchet : It is used to rotate the screw by turning it so that the object is gently held between the stud and the spindle of the screw
Thimble: It is a hollow cylinder and used to mark on the circular scale.
Sleeve: It is the base line on which the main scale is marked.
Main Scale: it reads length in the dimension of 1mm
Circular Scale: It reads length more precisely accurate up to 0.01mm or 0.005mm

Note :
The instrument is not error free. when the end of the screw and the surface of the stud are in contact with each other, the linear scale and the circular scale reading should be zero. If that is not achieved, the screw gauge is said to have an error called zero error.