Question

The number of circular divisions on the shown screw gauge is $50$. It moves $0.5\, mm$ on main scale for one complete rotation. Main scale reading is $2$. The diameter of the ball is

• A. $2.25 \,mm$
• B. $2.20 \,mm$
• C. $1.20 \,mm$
• D. $1.25 \,mm$

Answer 1

Answer: (C)

Zero error $=5\times\frac{0.5}{50}=0.05\,mm$
Actual measurement
$=2\times0.5\,mm+25\times\frac{0.5}{50}-0.05\,mm$
$=1\,mm+0.25\,mm-0.05\,mm=1.20\,mm$