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The whole idea behind creating scale drawings is to allow the drafter to create a drawing which is proportionately the same as the object it represents. Using a measuring device called a scale; we can create accurate drawings of both very large objects or very small objects and fit either on a standard size piece of paper. Drawing Scales are used because some objects are too big to fit on a sheet of drawing paper and others are so small that they could not be seen on a drawing. Scales are used as a way of helping to show large real life objects, such as buildings, on a drawing. The object must appear smaller than it really is so that it will fit onto a drawing.
A scale uses a ratio to show how the size of a real object compares to the size of the same object when it is drawn or made as a model. (Figure 7 )
For example, if the wall of a room is 4 m (4000 mm) long, and this is shown on a drawing as 400 mm long, then the ratio would be one to ten, because the real size of the object is ten times bigger than the size shown on the drawing. This ratio is written as 1:10
2:1
Pronounced "Two to One"
DOUBLE SIZE: 2 millimeters on paper =1 millimeter on the artifact
The drawing is twice as large as the object.
1:1
Pronounced "One to One"
FULL SIZE: 1 millimeter on paper =1 millimeter on the artifact
The drawing is the exact same size as the object.
1:2
Pronounced "One to Two"
HALF SIZE : 1 millimeter on paper =2 millimeters on the artifact
The drawing is half the size of the object.
1:4
Pronounced "One to Four"
QUARTER SIZE or 1 millimeter on paper= 4 millimeters on the drawing.
The drawing is one quarter the size of the object.
The choice of drawing scale that is to be used depends on:
- the size of the object being drawn
- how much detail needs to be visible in the drawing.
A drawing that is made to scale is a representation of an object either in its full size or with all its dimensions proportionately reduced. Very rare indeed is the case in architectural drawing when anything is represented greater than full size. The scale of “one eighth of an inch equals one foot " means that every one eighth of an inch on the drawing represents one foot in the finished structure. Three-quarter inch, one inch, one inch and a half, and three-inch scales are most frequently used for special drawings to illustrate clearly the important units in a design, typical details, or some unusual point in construction. . As a rule, capitals, bases, entablatures, decorations, stairs, sections of moldings, fireplaces, and mantels are drawn to the large scales. Working drawings are made to a scale of J inch to the foot, while preliminary sketches are laid out at t$ inch or £ inch to the foot, depending upon the size of the building. The scale to which a drawing is made is generally placed in the lower right-hand corner of the sheet and may be stated either in figures, thus:
1" = l'-0"; 1inch = l foot;
The scale should never be used to draw lines it should only be used for measuring. Here is an example of the scale would look like at ¼ " scale. If you drew a 4' line at ¼" scale the line would actually be 1" long because each foot is represented as a ¼" length.(Figure – 9)
Find the 0. To the left of the zero the inches are represented and to the right of the zero are feet. When you look at the inches you have to remember that there are 12" in a foot. When looking at the scale one should see that in the ¼" scale the inches are divided in inch and half inch increments. Now looking to the right at the foot increments, you notice that there are two strings of numbers- one high and one low. To figure out which numbers to read, look at the 0 and read the numbers that are in line with the 0.
An object with large dimensions may need to be drawn with a scale ratio such as 1:200 to be able to show the entire object within the drawing.
A smaller object, or a complex object that needs to be drawn with a lot of detail, may need to use a scale ratio such as 1:10.
Although a drawing or model of an object can be produced using any scale required, certain scales are commonly used for particular purposes:
- Complicated details use scales such as 1:2, 1:5, or 1:10
- Floor plans and elevations use scales such as 1:20, 1:50, 1:100, or 1:200
- Site plans use scales such as 1:200, 1:500, or 1:1250
- Location plans use scales such as 1:1250, or 1:2500.
- A scale rule has marks that can be used for measuring the dimensions of an object on a drawing. The scale that has been used to create a drawing will be shown on the drawing itself.
- To calculate the dimension of a real life object based on its dimension on a drawing, the scale on the rule and the scale of the drawing must be the same.
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