Power point presentation on scale and its different types

engg. Graphics

1. WELCOME SVPM’s INSTITUTE OF TECHNOLOGY AND ENGINEERING, MALEGAON ( Bk ) 2020-21

2. Lecturer:- Mr. Kadam S.P. (M.E. CDA/CAM) SVPM’S Institute of Technology and Engineering, Malegaon( Bk ) Automobile Engineering Department

3. 4. Scales – Reduced, Enlarged and Full Size Some objects like buildings, machines are big, some objects are very small ( parts used in wrist watches). Their drawing is required to be drawn proportionally reduced or enlarged. The proportion by which we are enlarging or reducing actual length of object on the drawing is known as scale. Scale size : Following scale sizes are used in engineering practice. Full size scale : The scale in which objects are drawn with actual measurements is known as full size scale. It is written as 1:1 Reduced scale: The scale in which objects are drawn with reduced proportion is known as reduced scale. It is written as 1:2, 1:10 etc. Enlarged scale: The scale in which objects are drawn with increased proportion is known as enlarged scale. It is written as 2:1, 10:1 etc

4. Representative Fraction (R.F.) It is the ratio of the length of object on drawing to the actual length of object For enlarging scale, R.F. is more than one. It is less than one for reducing scale. In metric measurements : 1 kilometer = 1000 meters 1 meter = 100 centimeters = 10 decimeter 1 centimeter = 10 millimeters 1 decameter = 10 meters 1 hectometer = 100 meters  

5. For measuring a scale, one must know : Its representative fraction. Maximum length to be measured. The units to be shown, for example, millimeters and centimeters.

6. Steps in constructing a scale Calculate the length of scale using the relation Draw two lines parallel to each other and some distance apart so that they give appearance as rule. Join ends by vertical line. Divide the line into required number of equal parts. Draw perpendicular lines at these division points. Mark zero at the end of first division. Subdivide only first main part to the left of zero into the required number of sub divisions. The subdivision represents fraction of main unit. The subdivisions are numbered to the left, starting from zero. The main units are numbered to the right, starting from zero. Units of measurement of main unit and its subdivisions are to be indicated. Name of the scale and R.F. should be mentioned below the scale