A scew gauge with a pitch of 0.5 mm and a circular scale with 50 divisions is used to measure the thickness of a thin sheet of aluminium. Before starting the measurement,it is found what when the two jaws of the screw gauge are brought in contact, the 45th division coincides with the main scale line and that the zero of the main scale is barely visible. What is the thickness (in mm) of the sheet. If the main scale reading is 0.5 mm and the 30th divisioni coincides wiht the main scale line?

Answer

`0.85`

Explanation

Least count `LC=0.5/50=0.01mm`
zero error
`ZE=(50-45)xx0.01=-0.05mm`
Main scale Reading (MSR)=0.5mm
Thickness
`t=0.5mm+30xx0.01mm-(-0.05mm)`
`t=0.85mm`