Engineering Scales

ENGINEERING SCALES

It is not always possible or convenient to draw drawings of an object to its actual size. For instance, drawings of very big objects like buildings, machines, etc., cannot be prepared in full size because they would be too big to accommodate on the drawing sheet. Drawings of very small objects like precision instruments, namely, watches, electronic devices, etc., also cannot be prepared in full size because they would be too small to draw and to read.

Special Unusual Scales: When you require to make measurements other than those given by the set of standard scales MI to M8, Special Unusual Scales have to be constructed. A convenient scale is always chosen to prepare the drawings of big as well as small objects in proportionately smaller or larger sizes. So, the scales are used to prepare a drawing at Full Size, Reduced Size or Enlarged Size.

1. Full Size Scale: If we show the actual length of an object on-a drawing, then the scale used is Full Size Scale. 

Designation of Full Size Scale: Scale I : 1. 

2. Reducing Scale: If we reduce the actual length of an object so as to accommodate  on drawing, then the scale used is called Reducing Scale. Such scales are used for the preparation of drawings of large machine parts, buildings, architectural drawings, etc.

 Designation of Reducing Scale: Scale 1 : x. (Example : Scale 1 : 20 ) 

3. Enlarging or Increasing Scale: Drawings of instruments, watches, etc., are made larger than their real size. These are said to be drawn in an Enlarging or Increasing Scale. 

Designation of Enlarging Scale: Scale x : I. (Example : Scale 20 : 1 )