PRIN. OF DRAFTING AND SHOP DRAWINGS - OD1641 - LESSON 1/TASK 4
They are the same weight as hidden lines but are about twice as long.
(8) Cutting Plane Line.
These lines indicate an imaginary cut, and arrows are
used to show the direction the workman is to look at the sectional view.
(9) Long Break Line.
These are space savers for the draftsman.
They do not
change the actual length indicated by the dimension, but make it possible for the
draftsman to show an object for which he would not otherwise have room.
(10) Short Break Line. These are used to indicate that the draftsman has removed
part of an outer surface to reveal the inside structure.
They usually come in
pairs.
b. Sections. A sectional view allows you to look inside an object shown on a shop
drawing.
Sectional views are necessary for a clear understanding of complicated
parts. On simple drawings, a section may serve the purpose of an additional view.
(1) Full Section, (figure 79 on the following page).
The
object
is
cut
completely through, showing the whole view in section.
(2) Offset Section, (figure 80 on the following page).
A joggle or offset is in
the cutting plane.
(3) Half Section, (figure 81 on page 91).
Two cutting planes meet at right
angles at the center line.
(4) Revolved Section, (figure 82 on page 91).
This is a drawing within
a
drawing, which eliminates extra views of rolled shapes, ribs, etc.
(5) Removed Section, (figure 83 on page 92). This serves the same purpose as the
revolved section, but instead of being drawn on the view, it is set off or shifted
to some adjacent place on the paper.
It may be enlarged to facilitate detailing
and dimensioning.
(6) Broken-out Section, (figure 84 on page 92). This is done by removing a part
of the outside surface when only a small area of the inside need be shown.
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