1. Line Conventions Line Conventions Introduction to Engineering DesignTM
Unit 1 – Lesson 1.2 – Intro to Technical Sketching
Line Conventions
Project Lead The Way, Inc.
Copyright 2007

2. Line Conventions
Introduction to Engineering DesignTM
Unit 1 – Lesson 1.2 – Intro to Technical Sketching
Line Conventions
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.
Project Lead The Way, Inc.
Copyright 2007

3. Line Conventions
Introduction to Engineering DesignTM
Unit 1 – Lesson 1.2 – Intro to Technical Sketching
Line Conventions
Construction Line
Construction Line: Very lightly drawn lines used as guides to help draw all other lines and shapes properly.
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?
Project Lead The Way, Inc.
Copyright 2007

4. Line Conventions Object Lines:
Introduction to Engineering DesignTM
Unit 1 – Lesson 1.2 – Intro to Technical Sketching
Line Conventions
Object Line
Object Lines:
Used to define the object; they are thickest and darkest lines on a sketch.
Object Line
Project Lead The Way, Inc.
Copyright 2007

5. Line Conventions Hidden Line:
Introduction to Engineering DesignTM
Unit 1 – Lesson 1.2 – Intro to Technical Sketching
Line Conventions
Hidden Line
Hidden Line:
Lines used to show interior detail that is not visible from that side of the part.
Hidden Line
Project Lead The Way, Inc.
Copyright 2007

6. Line Conventions
Introduction to Engineering DesignTM
Unit 1 – Lesson 1.2 – Intro to Technical Sketching
Line Conventions
Center Line
Center Line: Lines that define the center of arcs or circles; they are half as thick as an object line.
STOP PRESENTATION: Students have the line conventions needed for the activities in Lesson 1.2.
Center Line
Project Lead The Way, Inc.
Copyright 2007

7. Line Conventions
Introduction to Engineering DesignTM
Unit 1 – Lesson 1.2 – Intro to Technical Sketching
Line Conventions
Short-Break Line
Short-Break Line: A freehand drawn line that shows where a part is
broken to reveal detail behind the part.
STOP PRESENTATION: Students have the line conventions needed for the activities in Lesson 1.2.
Project Lead The Way, Inc.
Copyright 2007

8. Line Conventions
Introduction to Engineering DesignTM
Unit 1 – Lesson 1.2 – Intro to Technical Sketching
Line Conventions
Section Lines: Lines used to define where there is material after a part of the object is cut away.
Section Line
STOP PRESENTATION: Students have the line conventions needed for the activities in Lesson 1.2.
Section Line
Project Lead The Way, Inc.
Copyright 2007

9. Line Conventions Dimension Lines:
Introduction to Engineering DesignTM
Unit 1 – Lesson 1.2 – Intro to Technical Sketching
Line Conventions
Dimension Lines:
Lines that are used to show distance or measurement.
Arrows are drawn on the ends to show where the dimension line starts and ends.
The dimension is usually located in the middle of this line.
Understanding Line types and when to use them will help your sketches look cleaner and more professional.
Dimension Line
Dimension Line
Project Lead The Way, Inc.
Copyright 2007

10. Line Conventions Extension Lines:
Introduction to Engineering DesignTM
Unit 1 – Lesson 1.2 – Intro to Technical Sketching
Line Conventions
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.
Understanding Line types and when to use them will help your sketches look cleaner and more professional.
Extension Line
Project Lead The Way, Inc.
Copyright 2007

11. Line Conventions Long-Break Lines:
Introduction to Engineering DesignTM
Unit 1 – Lesson 1.2 – Intro to Technical Sketching
Line Conventions
Long-Break Line
Long-Break Lines:
Used to shorten very long objects that do not change in detail.
The line is usually represented as a jagged cut or break.
Understanding Line types and when to use them will help your sketches look cleaner and more professional.
Project Lead The Way, Inc.
Copyright 2007

12. Line Conventions Leader Lines:
Introduction to Engineering DesignTM
Unit 1 – Lesson 1.2 – Intro to Technical Sketching
Line Conventions
Leader Line
Leader Lines:
Leader lines are used to show dimensions of arcs and circles.
Leader Line
Project Lead The Way, Inc.
Copyright 2007

13. Precedence of Lines
Complex object sketches may require different line types to overlap
Line precedence must be used
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

14. Precedence of Lines Examples
Object lines has precedence over hidden lines
Object line has
precedence over center line