Scale is a measuring device that enables designers to represent accurately the size of an object in a technical drawing. The term scale describes the ratio of the drawing size relative to the actual size of the object. When you draw an object to scale, the drawing represents a ratio of the object size. With scale,  you can draw large objects that are too big to be drawn full size at a reduced size or objects that too small to an enlarged size. Architects, engineers and other designers use different types of scales to prepare technical drawing.  Some of the most common scales include metric scale, architects’ scale etc.

1. Metric scale: based on proportional ratio.  It describes the ratio of the drawing compared to the actual size of the object. The first number of the equation describes the size of the drawing and the second number describes the actual size of the object being drawn. Measurements are expressed in the smallest unit- millimeters.  Metric scale can be classified in the following categories:

a) Full scale: – the ratio are equal. The drawing is the same size as the object. For example:

1:1  Full size

5:5

b) Reducing scale: – the object is represented smaller in a drawing

1:2 drawing is half the size of the object

1:10 drawing is 1/10th the size of the object

1:50 drawing is 1/50th the size of the object

c) Enlarging scale: : – the object is represented larger in a drawing

2:1 drawing 2 times larger the object

4:1 drawing 4 times larger the object

2. Imperial scale: based on fractional ratio. For example:

1”=1” Full size

¼” = 1’-0”

1/8” = 1’-0”

3/8” = 1’-0”

¾” = 1’-0”

Example:

The length of a stadium is 100 m and its width is 75 m.  If 1 mm represents 25m, what would be the dimensions of the stadium drawn on a sheet of paper?

Solution:

You can take an intuitive approach to this problem:

100 yards by 75 yards
100 m = 4 mm  (HINT:  100 / 25)
75 m = 3 mm (HINT:  75 / 25)
Therefore, the dimensions would be 4 mm by 3 mm.
Or you can establish a proportion:
(Notice that the inches are all on the top and the yards are all on the bottom
for this solution.  Other combinations are possible.)

 Length:25x = 100 x = 4 mm Width:25y = 75 y = 3 mm

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