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Scales and Measurements
There are Basicity two types of scales used on prints:
Engineers Scale " decimal inch ".
When drawings are created some typical scales are: 1/4, 1/2, Full (1=1) for
mechanical drawings. For
example a 1/4 scale drawing means the object is drawn a quarter inch its actual
size on the sheet. Metric
Scale "millimeters" Drawings are drawn in millimeters instead of decimal inch .
The conversion factor
from millimeters to decimal inch is 25.4 divided by the decimal inch.
For example the scale of a drawing as noted on drawing sheet 1=2 (half) this
means if this object where
to exist in the real world , that 1" on the object would equal 2" on the drawing
sheet. If you wanted to
enlarge an object on the drawing sheet you would just reverse the values 2" on
the drawing would equal
1" on the object.
The scale of a drawing is usually noted in the titleblock or below the view of
the object that differs in
scale to that given in the titleblock.
Rulers are used for linear measuments the most common ruler in a machine shop
are the bench and
steel ruler. Both edges of both sides are graduated. The rulers measure in 1"
(1.00),
1/4" (.25), 1/8" (.125), and 1/16" (.0625) increments.
Linear measure refers to measuring the straight line
distance between two points. There are two measur
ing systems used , they are decimal/inch and metric systems. Your shop work may
require you to change
back and forth between, feet, and millimeters.
Converting feet to inches:
7 ft = 7 X 12 = 84 in
27.35 ft. = 27.35 X 12 = 328.2 in
4 19/64 ft = 275/64 X 12 = 51.5625 = 51 9/16 in.
Converting Inches to feet:
109 in = 109 / 12 = 9 ft. 1 in.
2191/4 in. = 2191/4 / 12 = 18 ft. 31/4 in.
28.7 in = 28.7 / 12 = 2 ft. 4.7 in.
Converting Inches to Millimeters:
16 in. = 16 X 25.4 = 406.4 = 406 mm
93.375 in. = 93.375 X 25.4 = 2371.725 = 2371.73m
1/16 = 1/16 X 25.4 = 1.5875 = 1.6 mm
Converting Millimeters to inches:
1789 mm = 1789 / 25.5 = 70.4 in
9.32 mm = 9.32 / 25.4 = .3669 = 367 in.
360.5 mm = 360 / 25.4 = 14.19 in.
Converting fractions to decimals :
21/100 = 21 / 100 = .21
divide the top " numerator " by the bottom "denominator"
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