SCALES in ENGINEERING GRAPHICS/DRAWING

SCALES: It is always convenient to represent objects to their actual size in drawings, if their size permits. eg. A 200 mm diameter plain disc should be represented by a circle of 200 mm diameter on the Drawing sheet. This gives complete information of the object. When drawings are prepared equal to the actual size of the object, the scale is said to be full size scale and the drawings are said to be full size drawings. However, it is not always possible to make drawings of all objects, such as large machines, buildings, town plans, etc. to their actual size. When the objects are of very large sizes, the actual Dimensions of the object have to be reduced on some regular proportion to make their drawings on the sheet. eg. A rectangular plot of size 25m X 10m can be represented by a rectangle of 250 mm X 100 mm. The scale selected in the present case is 1 mm = 0.10 m. In other words 1 mm on the drawing represents 0.10 m length of the object. When the drawings are prepared smaller than the actual size of the object, the scale is said to be reducing scale and the drawings are said to reduce sized drawings. Similarly very small objects, such as gear mechanism of a wristwatch, components of an electronics instrument, atoms configuration, etc., are shown by drawing them larger then their actual size. When the drawings are prepared larger than the actual size, the scale is said to be an enlarging scale and the drawings are said to enlarge sized drawings. This is being illustrated by drawing of a bottle. Examples for scales:::::: Enlarge Scale 3:1, 2:1 Full Scale 1:1 Reduced scale 1:2, 1:3, 1:5 Enlarge Size Drawings Full Size drawing Reduce Size Drawings Engineering Drawing BY GSK