INTRODUCTION TO SCALE : Scales are made of wood, steel, celluloid plastic, or cardboard. 15 cm long and 2 cm wide or 30 cm long and 3 cm wide level scales are in Common use. They are ordinarily around 1 mm thick. However, a 15 c.m. long and 2 c.m. wide scale is considered a Standard length of scale. By using scale, small components can be drawn with the same size as the components are actually. A 150 mm long pen or 175 mm long pencil may be shown by a drawing of 150 mm length or 175 mm length respectively. Drawings of the same size as the objects are called full-size drawings and ordinary full-size scales are generally used to draw such drawings. A scale is determined by the ratio of the dimensions of an element as represented in a drawing to the actual dimensions of the same element. This is called R.F. or Representative Fraction of Scale. The scales are generally classified as : (1) Plain scales (2) Diagonal scales (3) Vernier scales (4) Comparative scales (5) Scale of chor