image optically instead of contact-
section. Where necessary, the section lines may be
printing.
Prints produced by this
connected by a line of short, heavy dashes indicating
process will usually be marked
the exact path of the cutting plane.
"Reduced Size Print-Do Not Scale."
e. Dimension lines. Dimension lines are
(b) Brownline prints. Brownline
thin (light) unbroken lines with arrowheads used to
paper has the same function in the ozalid process as
indicate the extent of a dimension on a drawing. The
the brown papers do in the blueprint process. They
dimensions may be placed above the dimension line,
produce brown lines on a transparent background and
on a break in the dimension, or, where space is
are often used as an intermediate for making blueline
limited, as close as possible to the end of the
prints. Brownline prints are often called sepia
dimension line. The extent of the dimension is from
intermediates.
arrow head to arrowhead, and is expressed in feet and
inches on civil engineering drawings.
(c) Special materials. Materials
are available for use with the ozalid process which
f. Extension lines.
When it is not
produce a large variety of results, including many
convenient to draw a dimension line directly between
colored lines on white paper or colored lines on a
the visible lines it applies to, the visible line is
clear plastic background.
extended by a thin (light) unbroken extension line
which almost touches the end of the visible line. The
extension line indicates the extent of the dimension
lines which have an arrow touching it.
1-3.
LINE CONVENTIONS
g. Break lines. The break line indicates
Lines are symbols used on prints to show
that the object has been shortened to save space on
information necessary for construction. Figure 1-1
the drawing. The true length is indicated by the
shows the types of lines commonly used on drawings
dimension specified. The long break line is a thin
and prints.
(light) line interrupted by a z-shaped symbol. The
a. Visible lines. A heavy- or medium-
short break line convention varies with shape and
weight unbroken line is used for the primary feature
material, and indicates that part of the object has been
of a drawing. For drawings of objects, this line
cut away to show section detail or hidden features.
convention represents the edges, the intersection of
1-4.
SCALES AND SCALING
two surfaces, and the surface limit that is visible from
the viewing angle of the drawing. This line is often
Measuring dimensions on a print is called
called the outline.
scaling. Due to possible distortion of the print,
scaling should be avoided as much as possible.
b. Hidden lines. A medium-weight line
When scaling is essential, however, be sure to check
of evenly spaced short dashes represents an edge, the
for accuracy by applying the scale you are using to
intersection of two surfaces, and the surface limit
one or more of the important dimensions normally
which is not visible from the viewing angle of the
shown on a print.
drawing.
a. Types of scales
c. Center lines.
A thin (light) line
composed of alternate long and short dashes is called
(1) Architects'. Architects' scales (1, fig.
a center line. It is used to signify the center of a
1-2) are divided proportionally into feet and inches
circle or are and to divide objects into equal or
and are generally used in scaling drawings for
symmetrical parts.
machine and structural work.
The triangular
architects' scale usually contains 11 scales, each
d. Cutting plane lines. A pair of short,
subdivided differently. Six scales read from the left
heavy lines with arrowheads projected at 900
end, while five scales read from the right end. 1,
indicates the cutting plane when a drawing includes a
figure 1-2 shows how the 3/16-inch subdivision at the
section. Letters (A-A, B-B. etc.) are usually placed at
end
the arrowheads to identify the section.
The
arrowheads show the viewing direction of the
1-3
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