1. Replicating Objects: Alphabet of Lines
Lesson DD: A3-2
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

2. Identify and describe each type of line associated with the alphabet of lines.
Explain the meaning and precedence of lines.
Learning Objectives
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

3. Terms to Know Alphabet of lines Cutting-plane line Leader
Phantom lines
Break line
Dimension line
Line contrast
Section lines
Centerlines
Extension lines
Line precedence
Stitch line
Chain line
Hidden line
Object lines
Viewing-plane line
Terms to Know
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

4. Alphabet of Lines
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

5. Types of Lines Alphabet of Lines
Made up by various combinations of weight and type of lines
Weight of lines (thick or thin) and type of lines have specific meanings in all technical drawings
Types of Lines
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

6. Each line on a technical drawing should be sharp, crisp and dark and of the correct thickness so it reproduces easily.
No variation in darkness among lines should be present, only variations in thickness.
Line contrast: variation in line thickness
Types of Lines
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

7. American Society of Mechanical Engineers (ASME) recommends two-line thickness with bold lines (twice as thick as thin lines).
Standard line thicknesses are 0.6 mm for thick lines and 0.3 mm for thin lines.
Types of Lines
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

8. Types of Lines Alphabet of Lines Break Lines Object Lines Hidden Lines
Phantom Lines
Stitch Lines
Section Lines
Chain Lines
Centerlines
Dimension Lines
Extension Lines
Leaders
Cutting-plane Lines
Viewing-plane Lines
Types of Lines
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

9. Types of Lines Object Lines
Describe the visible surface or edges of an object
Drawn as thick lines
Use a soft lead (H or F)
Types of Lines
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

10. Types of Lines Hidden Lines Represents an invisible edge on an object
Drawn as a thin line, half as thick as an object line
Best way to draw hidden lines is to draw dash lengths and spaces by eye
Types of Lines
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

11. Types of Lines Section Lines
Used in the view of a section to show where the cutting-plane line has cut through material
Drawn as thin lines
Drawn equally spaced but should not be parallel or perpendicular to any object line
Types of Lines
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

12. Types of Lines Centerlines
Used to locate the center of a circle or an arc and to represent the center axis of a circular or symmetrical form
Drawn as thin lines
Should start and end with long dashes and extend a short distance past an object
Types of Lines
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

13. Types of Lines Dimension Lines
Used to indicate a particular dimension of an object
Drawn as a thin line
Capped on the ends with arrowheads and broken along its length to allow space for the dimension number
Types of Lines
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

14. Types of Lines Extension Lines
Used to establish the extent of a dimension
Drawn as thin lines
May cross object lines, centerlines, hidden lines and other extension lines
Do not cross dimension lines
Types of Lines
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

15. Types of Lines Leaders a.k.a. Leader Line
Used to connect a specific note or description to a feature
Drawn as a thin line
Has a shoulder at one end and an arrowhead at the other end pointing to the feature
Types of Lines
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

16. Types of Lines Cutting-plane and Viewing-Plan Lines
Both drawn as thick, dashed lines with arrowheads at both ends
Arrowheads are perpendicular to the line
Cutting-plane Lines
Used to identify where a sectional view is taken
Types of Lines
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

17. Types of Lines Viewing-plane Lines
Used to identify where a view is taken for view enlargements or for partial views
Types of Lines
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

18. Types of Lines Break Lines Used to indicate a break in an object
2 types of break lines
Short Break
Thick
Drawn freehand
Long Break
Thin
Drawn with instruments or templates
Types of Lines
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

19. Types of Lines Phantom Lines
Used to identify alternate positions of moving parts, adjacent positions of related parts, repetitive details and contours of filleted and rounded corners
Drawn as thin lines
One long and two short dashes alternately spaces
Types of Lines
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

20. Types of Lines Stitch Lines
Used to indicate the location of a stitching or sewing process
2 types of stitch lines
Drawn as a series of thin, short dashes
Drawn as a series of small dots
Types of Lines
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

21. Types of Lines Chain Lines
Used to indicate that the portion of the surface next to the chain line receives some specified treatment
Drawn as a thick line
Alternately spaced long and short dashes
Types of Lines
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

22. Meaning and Precedence of Lines
Visible line or hidden line has 3 possible meanings:
Edge view of a surface
Intersection of two surfaces
Contour view of a curved surface
Meaning and Precedence of Lines
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

23. Meaning and Precedence of Lines
Since no shading is used on technical drawings, all views of an object need to be examined to determine meaning of lines.
When drawing multi-views, one type of line often falls in line with another.
Drafter needs to decide which of the two lines to draw.
Meaning and Precedence of Lines
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design

24. Meaning and Precedence of Lines
Line Precedence
The importance of one type of line over another
Based on the following:
Object lines take precedence over hidden lines and centerlines.
Hidden lines take precedence over centerlines.
In sectioning, cutting-plane lines take precedence over centerlines.
Meaning and Precedence of Lines
Illinois CTE Curriculum Revitalization Initiative - Drafting and Design