A steel rule is exactly what it sounds like... a rule manufactured from either spring or stainless steel that feature either metric or imperial (or both) scales along its length.
For units of metric system the least count of steel rule is 0.5mm.
A try- square is a woodworking tool used for marking and measuring a square piece of wood. The square refers to the tool's primary use of measuring the accuracy of a right angle (90 degree angle); to try a surface is to check its straightness or correspondence to an adjoining surface.
The vernier bevel protractor is a precision instrument meant for measuring angles to an accuracy of 5 minutes.
The Least count of vernier bevel protractor is 5' (Five Minutes)
The value of each Vernier scale division of Vernier bevel protractor is 1 degree 55 minutes.
To get the least count of 5 minutes (5') in a vernier bevel protractor the 23 degree main scale is divided into 12 equal parts on vernier scale.
Following are the parts of a vernier bevel protractor.
Stock : – This is one of the contacting surfaces during the measurement of an angle. Preferably it should be kept in contact with the datum surface from which the angle is measured.
Dial:– The dial is an integrated part of the stock. It is circular in shape, and the edge is graduated in degrees.
Blade:- This is the other surface of the instrument that contacts the work during measurement. It is fixed to the dial with the help of the clamping lever. A parallel groove is provided in the centre of the blade to enable it to be longitudinally positioned whenever necessary.
Locking Screws:- Two knurled locking screws are provided, one to lock the dial to the disc, and the other to lock the blade to the dial.