Identify
standard scales
See textbook pages
76-81
The function
of scales
Scales allow us to represent an
object proportionately at a size that fits on a manageable sheet of paper.
If we were to draw a house at a scale of 1
to 1, the sheet of paper would have to be about 50 feet, or 15 meters
long, which is not very manageable.
It is important that the features of the object are drawn proportionately
to other features of the object in order to ensure there are no interferences,
and that suitable clearance is allowed for. For example, a person needs about
2’-6”, or 750mm to walk freely down a passageway. If the drawing is drawn
to scale showing this size passageway, then we know that when it is built
there will be adequate room for a person to walk.
Imperial and
Metric scales
The Imperial scales are expressed in absolute terms:
1/4”=1’-0”
The Metric scales are expressed in relative
terms:
1 : 50.
It is easy to determine in the Metric scale what the relative
size of the drawing is: 1 unit on the drawing is equal to 50 units in
real life. It is not so easy to tell what the relative
size is in Imperial, but we can find out by doing the following
calculations:
1/4” =
1’- 0”
1/4” =
12”
1 = 12 x 4
1:48
Standard Scales
Imperial scales come in two
types: Architectural and Engineer.
Architectural
scales are used for scales up to 1/8”=1’-0” (1:96), usually for mechanical
and architectural drawings.
Engineer
scales use inches that are divided into multiples of 10, and are used for
scales from 1”=10’ (1:120) and larger. These scales are usually used
for civil drawings such as
highways or subdivisions.
Metric
scales can be used for all types
of drawings since they accommodate scales from 1:1 to 1: 1000 and larger.(
We just keep adding zeros to the number on the right.)
Accurate reading of scales
Architectural:
The full scale on an Architectural scale is divided into 16 units, each
1/16”. Two of these units would
be 1/8”, for would be 1/4”, and so on.
The smaller scales on the Architectural scale are
written on the ends of the scale. The last unit is divided into 12 or 6 so
an object can be measured to within 1” or 2” depending on the scale.
Engineer:
Engineer scales use inches divided into multiples of 10. The number of
units an inch is divided into is written at the end of each scale.
Metric:
Metric scales are always divided into 10 units, with the relative scale
written at the end. To understand the scale we must first understand the
Metric System.
1 meter (m) = 10 decameters
(dm) = 100 centimeters (cm) = 1000 millimeters (mm)
A scale of 1:10 would mean that 1 mm = 10 mm or 1 cm.
A scale of 1:1000 would mean that 1mm = 1000mm or 1 m.
See
SCALE CHART
|
