A screw gauge is a measuring instrument that can measure the dimensions up to \(1/100th\) of a \(millimetre\) or \(0.01 mm\). With the screw gauge, it is possible to measure the diameter of a thin wire and the thickness of thin metallic plates.
Construction of Screw gauge
Description of screw gauge:
The screw gauge contains a U shaped metal frame. A hollow cylinder is connected to one end of the frame. Grooves are cut on the inside surface of the cylinder through which a screw passes (shown in the above figure).
- On the cylinder parallel to the axis of the screw, there is a scale which is graded in millimetres. It is called Pitch Scale (PS).
- One end of the screw is connected to a sleeve. The head of the sleeve (Thimble) is split into \(100\) divisions called the Head scale.
- The end of the screw has a plane surface which is known as Spindle.
- A stud called Anvil is attached to the other end of the frame, just opposite to the tip of the screw. The screw head is fitted with a ratchet arrangement (safety device) to prevent the user from exerting undue pressure.
Uses of Screw gauge:
The important uses of screw gauge are as follows,
- It is used to measure the diameter of circular objects, mostly wires with an accuracy of \(0.001cm\).
- It can be used to measure the diameter of a wire.
- It can also be used to measure the thickness of a paper.