3. Lines of varying style and thickness are used
in specific ways to develop and communicate
graphic messages about an object’s
geometry. The next few slides show some
basic line conventions and their use.
Line Conventions
7. Line Conventions
Center Line:
Lines that define
the center of
arcs, circles, or
Symmetrical
parts. They are
half as thick as
an object line.
Center Line
Center Line
10. Line Conventions
Short-Break Line:
A freehand drawn
line that shows
where a part is
broken to reveal
detail behind the
part or to shorten a
long continuous
part.
Short-Break
Line
11. Line Conventions
Dimension
Line
Dimension
Line
• Dimension Lines: Lines
that are used to show
distance.
• Arrows are drawn on the
ends to show where the
dimension line starts and
ends.
• The actual distance is
usually located in the
middle of this line to let
you know the distance
being communicated.
12. Line Conventions
Extension
Line
Extension
Line
• Extension Lines: Lines
used to show where a
dimension starts and
stops on an object.
• Used with dimension
lines to properly
dimension an object.
• The line is 1/16” away
from the part as to not
get confused with the
object lines.
14. Line Conventions
• Leader Lines: Leader
lines are used to
show dimensions of
arcs, circles and to
help show detail.
Leader Line
Leader Line
15. Though these standards relate to
technical drawing, which is far more
precise than freehand sketching,
their conventions should be used as
a guide when sketching.
Line Conventions
16. When sketching complex objects,
different line types will often overlap
each other. Therefore, line precedence
must be exercised.
Precedence of Lines
17. The following are rules that govern line
precedence in sketches and technical
drawings.
• Object lines take precedence over hidden and
center lines.
• Hidden lines take precedence over center lines.
• Cutting plane lines take precedence over all
others.
Precedence of Lines
18. Precedence of Lines
Object lines take precedence over
the hidden lines.
An object line here takes
precedence over the center line.
19. Precedence of Lines
• Object lines take
precedence over the
center lines you
would see from the
hole.
• Object lines take
precedence over the
hidden lines you
would see from the
slot cut out in top
view.
An object line here takes
precedence over the center line.
An object line here takes
precedence over the hidden line.
Editor's Notes
Ask students after slide first appears: What do you notice about this sketch? (Making sure you lead them into looking at the different line conventions or types that appear in the sketch). Imagine if all the lines here had the same thickness, weight and consistency. What do you think this sketch would look like then?
STOP PRESENTATION: Students have the line conventions needed for the activities in Lesson 1.2.
The rest of this PowerPoint will be used in Unit 2.
STOP PRESENTATION: Students have the line conventions needed for the activities in Lesson 1.2.
STOP PRESENTATION: Students have the line conventions needed for the activities in Lesson 1.2.
Understanding Line types and when to use them will help your sketches look cleaner and more professional.
Understanding Line types and when to use them will help your sketches look cleaner and more professional.
Understanding Line types and when to use them will help your sketches look cleaner and more professional.
This will make more since to the students when they do the multiview sketch activities
You may want to save this slide until you start multiview sketch activity.