1. Introduction to Drafting and Design
Alphabet of Lines
Introduction to Drafting and Design
In this presentation, we are going to learn about the different lines that are used in a drawing.
The list of different lines is known as the alphabet of lines

2. What is the Alphabet of Lines?
Developed by the American Society of Mechanical Engineers (ASME).
The Alphabet of Lines is used to make a drawing neater and clearer to understand.
Different lines represent different aspects of a drawing.
So what is the Alphabet of Lines?
The alphabet of lines was developed by the American Society of Mechanical Engineers and is used by all drafters and engineers today.
It is used to make a drawing neater and clearer to understand.
Different lines represent different aspects of a drawing.

3. So what are these lines? Construction Lines Visible/Object Lines
Hidden Lines
Center Lines
Dimension Lines
Extension Lines
Phantom Lines
Long Break Lines
Short Break Lines
Cutting-plane Lines
Section Lines
Chain Lines
Leaders
Symmetry Lines
Border Lines
So what are these lines that are considered the Alphabet of Lines?
Construction lines
Visible/object lines
Hidden lines
Center lines
Dimension lines
Extension lines
Phantom lines
Long break lines
Short break lines
Cutting-plane lines
Section lines
Chain lines
Leaders
Symmetry lines
Border lines

4. Construction Lines Used to initially lay out a drawings.
Used for guidelines for lettering.
Drawn very light and thin so that they are barely visible.
Construction lines
Used to initially lay out a drawing
Used for guidelines for lettering
Drawn very light and thin so that they are barely visible
They should be drawn so light that they don’t have to be erased once the drawing is complete.

5. Visible/Object Lines Used to represent the visible edges of an object.
Should be the most prominent on the drawing.
Drawn thick and dark.
These are thicker than construction lines.
Visible/object lines
Used to represent the visible edges of an object.
Should be the most prominent on the drawing
Drawn thick and dark
These are thicker than construction lines.

6. Hidden Lines
Used to represent edges, surfaces or corners of an object hidden from view.
Drawn as thin, dark dashed lines.
Spacing can vary slightly.
Only the most important hidden parts are shown on the drawing to keep the drawings from becoming cluttered.
Hidden Lines
Used to represent edges, surfaces or corners of an object hidden from view.
Drawn as thin, dark dashed lines
Spacing can vary slightly
Only the most important hidden parts are shown on the drawing to keep the drawings from becoming cluttered.

7. Center Lines Used to show the center of circles and arcs.
Drawn as thin lines.
Drawn using two long dashes and a shorter dash.
To show the center of a round object, two centerlines are used so that the short dashes cross in the center.
Center lines
Used to show the center of circles and arcs
Drawn as thin lines
Drawn using two long dashes and a shorter dash
To show the center of a round object, two centerlines are used so that the short dashes cross in the center.

8. Dimension Lines Used for dimensioning and notes. Drawn as thin lines.
Drawn with arrowheads on each end and placed between extension lines.
The dimension is lettered above the dimension line approximately half way between the two extension lines.
Dimension lines
Used for dimensioning and notes
Drawn as thin lines
Drawn with arrowheads on each end and placed between extension lines
The dimension in lettered above the dimension line approximately half way between the two extension lines.

9. Extension Lines Used to extend dimensions from the related objects.
Drawn as thin lines.
Drawn with a short space between the object and line.
Extend about 3 mm beyond the dimension line.
Extension lines
Used to extend dimensions from the related objects
Drawn as thin lines
Drawn with a short space between the object and line.
Extend about 3 mm beyond the dimension line

10. Phantom Lines
Used to show objects that are not hidden but they are simply not in view.
Also used to indicate alternate positions of moving parts, lines of motion, adjacent parts and repetitive details.
Drawn as thin, dark lines.
Phantom lines
Used to show objects that are not hidden but they are simply not in view
Also used to indicate alternate positions of moving parts, lines of motion, adjacent parts and repetitive details
Drawn as thin, dark lines

11. Long Break Lines
Used to indicate parts of the object has been removed.
Used when it is desirable to shorten the view of a long part.
Long break lines are drawn thin with freehand “zigzags”.
Long break lines
used to indicate parts of the object has been removed
used when it is desirable to shorten the view of a long part
long break lines are drawn thin with freehand “zigzags”

12. Short Break Lines
Used to indicate parts of the object has been removed.
Used when it is desirable to shorten the view of a long part.
Short break lines are drawn thick and with freehand wavy lines.
Short break lines
Used to indicate parts of the object has been removed
Used when it is desirable to shorten the view of a long part
Short break lines are drawn thick and with freehand wavy lines

13. Cutting-plane Lines
Used to indicate the plane through which a cut was made.
A cutting plane line is usually a heavy line with long dashes with arrowheads at both ends of the line.
The arrowheads point to the surface to be viewed.
Cutting-plane lines
Used to indicate the plane through which a cut was made
A cutting plane line is usually a heavy line with long dashes with arrowheads at both ends of the line
The arrowheads point to the surface to be viewed

14. Section Lines
Used to indicate the surface in the section view imagined to have been cut along the cutting plane line.
Thin “cross hatching” lines drawn at a 45° angle.
Section lines
Used to indicate the surface in the section view imagined to have been cut along the cutting plane line
Thin “cross hatching” lines drawn at a 45° angle

15. Chain Lines
Used to indicate an area or portion of a surface that is to receive special treatment.
Represented by a long dash followed by a short dash followed by a long dash.
Chain lines
Used to indicate an area or portion of a surface that is to receive special treatment
Represented by a long dash followed by a short dash followed by a long dash

16. Leaders Used to point to notes or dimensions. Drawn as thin lines.
Consist of an arrowhead and angled line connected to a surface.
Arrowheads touch the object lines while the dot rests on a surface.
Leaders
Used to point to notes or dimensions
Drawn as thin lines
Consist of an arrowhead (or dot) and angled line connected to a surface
Arrowheads touch the object lines while the dot rests on a surface

17. Symmetry Lines Used when partial views of symmetrical parts are drawn.
It is a center line with two thick short parallel lines drawn at right angles to it at both ends.
Symmetry lines
Used when partial views of symmetrical parts are drawn
It is a center line with two thick short parallel lines drawn at right angles to it at both ends

18. Border Lines Used to outline the entire drawing.
They are a continuous thick line on the outer rim of the paper.
Border lines
Used to outline the entire drawing
They are a continuous thick line on the outer rim of the paper

19. Let’s look again…
Let’s take a look again at the picture that appeared at the beginning of this presentation

20. Hierarchy of Lines
If lines happen to overlap, then there is a hierarchy to which the lines show up.
The hierarchy of lines is as follows:
Object or visible line
Hidden line
Cutting Plane line
Center line
Break line
Dimension and extension lines
Sectioning lines
Hierarchy of Lines
If lines happen to overlap, then there is a hierarchy to which the lines show up
The hierarchy of lines is as follows:
Object or visible line
Hidden line
Cutting plane line
Center line
Break line
Dimension and extension lines
Section lines