PRIN. OF DRAFTING AND SHOP DRAWINGS - OD1641 - LESSON 1/TASK 4
Always locate a hole by dimensioning to its center point.
Make sure that the
center point of the hole is clearly defined by crossing the short sections of the
center lines. The long sections of the center lines may be dimensioned as if they
were extension lines.
FIGURE 70.
DIFFERENT WAYS TO DIMENSION
HOLES AND ARCS.
When using leader lines, always point the arrow end of the line at the center point
of the hole. Always finish the non-arrow end with a short horizontal section that
will guide the reader's eye into the dimension note. Always place dimension notes
so that they may be read from the bottom of the drawing.
(4) Dimensioning Angles and Holes. Figure 71 (on the following page) illustrates
several different ways to dimension angles.
It also illustrates the angular
(dimensioned with angles) and the coordinate (dimensioned using the center lines as
base lines) systems of dimensioning holes on an object.
80
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