Question

There is screw gauge having main scale division as well as pitch of circular scale is 0.5 mm. Circular scale has 100 divisions. If no object is placed then ‘0’ of main scale is not visible and 3 division lies below reference main scale if wire is placed in between jaws, reading on main scale is 5.5 mm and ${48}^{th}$ division matches with reference on main scale. The diameter of wire is

• A. 7.235 mm
• B. 6.225 mm
• C. 5.634 mm
• D. 6.125 mm

Answer 1

The correct option is B 6.225 mm

Least count = $\frac{0.5}{100}=0.005$ mm

Zero error $=(100-3)\times 0.005$

$=-97\times 0.005-0.485$ mm

Reading = MSR + CSR $\times$ L.C

$=5.5+48\times 0.005$

$=5.5+0.240=5.740$ mm

Actual diameter $=5.740+0.485$
$=6.225$ mm