Question

The positions of the ‘zeroes’ of the circular scale, with respect to the reference lines, (when the jaws are just put in contact), for two screw gauge X and Y, are as shown.

Screw gauge X has a main scale graduated in half millimeters and its circular scale has 50 divisions. The screw advances 3.5 mm, on the main scale, when given 7 complete rotations. 

‘Screw gauge Y has a main scale graduates in millimeters and its circular scale has 100 divisions. The screw advances 5 mm, on the main scale, when given 5 complete rotations. 

Four students reported the following basic information about the two ‘screw gauges’.

The complete correct reporting has been done by student

(1) A

(2) B

(3) C

(4) D

Answer 1

(1) A

For screw gauge X

Pitch = 3.5/7 mm = 0.5 mm 

Least count = 0.5/50 mm = 0.01 mm 

Zero error = + 10 x L.C = + 0.10 mm 

For screw gauge Y

Pitch = 5/5 mm = 1 mm 

Least count = 1/100 mm = 0.01 mm 

Zero error = –5 x L.C = – 0.05 mm