1. Alphabet Of Lines
Chapter 4

2. Introduction to the Alphabet of Lines
The use of line types on a drawing
are used to describe the various features of an object
to the person reading the print
In order to understand what the drafter is trying to get across
you must be able to understand the symbols and lines s/he uses.

3. Introduction to the Alphabet of Lines – Cont’d
A line is the most fundamental and perhaps the most important, single entity on a technical drawing
Lines help to illustrate and describe the shape of objects that will later become real parts.

4. Introduction to the Alphabet of Lines
Each line has a definite form and line weight.
The standard thick line weight varies from .030 to .038 of an inch.
The standard thin line weight varies from .015 to .022 of an inch.

5. The Alphabet of Lines Illustrated

6. 11 Main Line Types Visible (Object) Hidden Center Dimension Extension
Leader
Section
Cutting Plane
Phantom
Viewing Plane
Break

7. Visible Lines Also referred to as Object Lines Dark, heavy lines.
Show the outline and shape of an object.
Define features you can see in a particular view.

8. Visible or Object Line

9. Hidden Lines Light, narrow, short, dashed lines.
Shows the outline of a feature that can not be seen in a particular view.
Used to help clarify a feature, but can be omitted if they clutter a drawing.

10. Hidden Lines

11. Center Lines Thin line consisting of long and short dashes.
Shows the center of holes, slots, paths of rotation, and symmetrical objects.

12. Center Lines

13. Dimension Lines Dark, heavy lines.
Show the length, width, and height of the features of an object.
Terminated with arrowheads at the end.

14. Center Lines

15. Extension Lines
Used to show the starting and stopping points of a dimension.
Must have at least a 1/16th space between the object and the extension line.
Extension Line
Dimension Line

16. Extension Lines

17. Leader Lines Thin lines.
Used to show the dimension of a feature or a note that is too large to be placed beside the feature itself.
Leader Line

18. Leader Lines

19. Cutting Plane Lines
Thick broken line that is terminated with short 90 degree arrowheads.
Shows where a part is mentally cut in half to better see the interior detail.

20. Cutting Plane Lines

21. Section Lines Thin lines Usually drawn at 45 degrees
There are different types of section lines
depending on the type of material being cut through

22. Section Lines
Indicates the material that has been cut through in a sectional view
Use to show where the cutting-plane line has cut through material

23. Section Lines

24. Break Lines
Used to break out sections for clarity or for shortening a part.
Three types of break lines with different line weights.
Short Breaks.
Long Breaks.
Cylindrical Breaks.

25. Short Break Lines Thick wavy line.
Used to break the edge or surface of a part for clarity of a hidden surface.
Short Break Line

26. Long Break Lines Long, thin lines.
Used to show that the middle section of an object has been removed so it can be drawn on a smaller piece of paper.

27. Cylindrical Break Lines
Thin lines.
Used to show round parts that are broken in half to better clarify the print or to reduce the length of the object.

28. Phantom Lines
Thin lines made up of long dashes alternating with pairs of short dashes.
Three purposes in drawings.
1. To show the alternate position of
moving parts.
2. To show the relationship of parts
that fit together.
3. To show repeated detail.

29. Alternate Position
Phantom lines can show where a part is moving to and from.
Eliminates the confusion of thinking there may be 2 parts instead of just 1.
Phantom Lines

30. Phantom Line

31. Relationship of Mating Parts
Phantom lines can also show how two or more parts go together without having to draw and dimension both parts.

32. Repeated Detail Phantom lines can show repeated detail of an object.
Saves the drafter time and the company money.
Less chance of drafter error.

33. OnLine Slide Show
There is a brief and easy to follow demonstration of the Alphabet of Lines on line

34. Summary
Now that we have discussed the 11 main line types, you should be able to do the following:
1. Identify the alphabet of lines.
2. Identify where the line types are used.
3. Produce the lines with various
line weights.