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Figure 2-10.—Laying out a drip pan with dividers. |
measurement from a scale to the work, set one point
of the dividers on the mark and carefully adjust the
other leg to the required length, as shown in figure 2-5.
To scribe a circle, or an arc, grasp the dividers
between the fingers and the thumb, as shown in figure
2-6. Place the point of one leg on the center, and swing
the arc. Exert enough pressure to hold the point on
center, slightly inclining the dividers in the direction
in which they are being rotated.
TrammelPoints
To scribe a circle with a radius larger than your
dividers, you should select TRAMMEL POINTS. The
method of adjusting the points, as shown in figure 2-7,
is to set the left-hand point on one mark, slide the
right-hand point to the required distance, and tighten
the thumbscrew. The arc, or circle, is then scribed in
the same manner as with the dividers.
need a right angle for a layout. Breakout your dividers,
a scriber, and a straightedge. Draw a base line like the
one labeled AB in figure 2-8. Set the dividers for a
distance greater than one-half AB; then, with A as a
center, scribe arcs like those labeled C and D. Next,
without changing the setting of the dividers, use B as
a center, and scribe another set of arcs at C and D.
Draw a line through the points where the arcs intersect
and you have erected perpendiculars to line AB,
forming four 90-degree, or right, angles. You have also
bisected or divided line AB into two equal parts.
Constructing a right angle at a given point with a
pair of dividers is a procedure you will find useful
when making layouts. Figure 2-9 shows the method
for constructing a right angle at a given point.
Constructing a 90-degree, or right, angle is not
difficult if you have a true, steel square. Suppose that
you have no square or that your square is off and you
Figure 2-7.—Setting trammel points.
Figure 2-5.—Setting the dividers
Figure 2-6.—Scribing an acr/circle with dividers
Figure 2-8.—Constructing a 90-degree angle by bisecting a
line.
Figure 2-9.—Constructing a 90-degree angle at a given point
2-3
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