CONVENTIONAL LINES
CONVENTIONAL LINES
8LAMAGE
FACING
14 X 3 PROF.
DEEP
In a technical drawing, each type of line
has its own significance. Each is
distinguished from the other by a
particular thickness or shape.
50
13
40
20
24
45°
45
20
80
The thrust equipped with two lathed holes
drawn above in isometric projection, is
also portrayed on the right by three
views. This drawing will serve to
illustrate, in the following pages, the
principal lines found in technical drawing.
CONVENTIONAL LINES
A
OBJECT LINE OR VISIBLE
OUTLINE
CONVENTIONAL LINES
The object line or visible
outline is made of a
continuous line that portrays
the visible forms of the object.
It is a thick line, its thickness
chosen to clearly show the
shape.
OBJECT LINE OR VISIBLE
OUTLINE
CONVENTIONAL LINES
B
HIDDEN FEATURE LINE
B
CONVENTIONAL LINES
The hidden feature line is
made of a dashed line that
portrays surfaces and edges
that are hidden from view.
The line is medium, half the
width of the one chosen for the
visible outline.
B
HIDDEN FEATURE LINE
CONVENTIONAL LINES
C
C
THE CENTER LINE
CONVENTIONAL LINES
The center line is made
from phantom lines. It is
used to designate the axes
of round or circular shaped
objects.
The line is fine, the width
half that of the one used for
hidden features.
THE CENTER LINE
CONVENTIONAL LINES
D
DIMENSION LINE
CONVENTIONAL LINES
The dimension line is a
fine line ending with an
arrow.
Its purpose is to enter
and specify the
placement of the
dimensions.
DIMENSION LINE
CONVENTIONAL LINES
The dimension is a value
used to indicate size in a
technical drawing.
40
20
This value is given in
millimetres.
40°
45
80
DIMENSION
CONVENTIONAL LINES
50
40
13
20
24
40°
45
20
E
80
EXTENSION LINE
CONVENTIONAL LINES
50 Extension lines are fine
lines that indicate the
placement of the
dimensions.
40
13
20
24
40°
45
20
80
EXTENSION LINE
CONVENTIONAL LINES
50
Ø8
FACING
Ø14 x 3 DEEP
40
13
20
24
F
40°
45
20
80
THE LEADER
CONVENTIONAL LINES
The leader is used
to indicate the part
50the drawing to
of
which a note refers.
Ø8
FACING
Ø14 x 3 DEEP
40
13
20
24
40°
45
20
80
THE LEADER
CONVENTIONAL LINES
50
G
Ø8
FACING
Ø14 x 3 DEEP
40
13
20
24
40°
45
20
80
CUTTING PLANE LINE
CONVENTIONAL LINES
50
Ø8
FACING
Ø14 x 3 DEEP
40
13
20
The cutting plane line
is very thick; this line is
used to designate where
an imaginary cut took
place.
24
40°
45
80
CUTTING PLANE LINE
INFORMATION ON
CUTS
CONVENTIONAL LINES
50
Ø8
FACING
Ø14 x 3 DEEP
40
13
20
24
40°
H
45
20
80
SECTION LINES
CONVENTIONAL LINES
Sections lines are fine
lines used to indicate the
surface imagined to
have been cut.
50
Ø8
FACING
Ø14 x 3 DEEP
40
13
20
24
40°
45
20
80
SECTION LINES
CONVENTIONAL LINES
50
H
40
13
20
24
40°
45
20
H
Ø8
FACING
Ø14 x 3 DEEP
80
THE SHORT BREAK LINE
CONVENTIONAL LINES
Ø8
FACING
Ø14 x 3 DEEP
The short break line is a
thick, irregular line used
to indicate a partial cut.
This line is drawn
freehand.
40
50
13
20
24
40°
45
20
80
THE SHORT BREAK LINE
The long break line is a
fine line used to shorten
the view of a long part
that can not be shown full
length.
THE LONG BREAK LINE
CONVENTIONAL LINES
SUMMARY
LINE
NAME
PURPOSE
THICKNESS
Thick
A
Object line or visible
outline
Portrays visible forms.
B
Hidden feature line
Portrays surfaces and edges that are
hidden from view
C
Center line
D
Extension line
Is used to indicate the dimension.
Fine
E
Dimension line
Is used to indicate the dimension.
Fine
F
Cutting plane line
Indicates the placement of an
imaginary cut.
G
Section lines
Indicate the surface imagined to have
been cut.
H
Break line
J
Leader
Portrays the center of a round or circular
object.
Used to shorten the view of a part.
Indicates the part of a drawing to which
a note refers
100 %
Medium
50 %
Fine
25 %
Very thick
Fine
Fine
Fine
The section view allows one
to see inside the object. It
makes the object simpler to
understand by eliminating
hidden feature lines.
The cutting plane line show
where the object is cut. The
arrows indicate the point of
view of the observer.
Section lines emphasise
which part has been cut in
the section view.
We presume that the part
between the cutting plane
line and the observer has
been removed.
The section is drawn in a
view adjacent to the cutting
plane line.
SUMMARY
Bibliography
GIESECKE, Frederick E., MITCHELL, Alva, SPENCER,
Henry Cecil, HILL, Ivan Leroy, GYGDON, John Thomas et
NGUYEN, Dinh N. « Dessin technique », Montréal,
Éditions du Renouveau Pédagogiques inc., 1982, 769 p.
JENSEN, C.H. « Dessin industriel », Montréal, McGrawHill, 1972, 752 p.
STIRLING, Norman. « Éléments de dessin industriel »,
Montréal, HRW, 1979, 372 p.