1. Prepared by: Asst. lecture
University Of Warith Al-anbiyaa
College of Engineering
AC & Ref. Technologies Department
First Class
Line Convention
Prepared by: Asst. lecture
Karrar A.Ahmed Hammodi

2. Orthographic Projection
Rules for Line Creation and Use

3. Using Hidden Lines
Hidden lines represent edges and boundaries that cannot be seen.

4. Creating Hidden Lines Rule 1:
The length of the hidden line dashes may vary slightly as the size of the drawing changes.

5. Creating Hidden Lines Rule 2:
Hidden lines should always begin and end with a dash,
Exception: When the hidden line begins or ends at a parallel visible or hidden line.

6. HIDDEN LINE PRACTICE
Hidden line should join a visible line, except it extended from the visible line.
Leave
space
Correct
Join
No !

7. HIDDEN LINE PRACTICE
Hidden line should join a visible line, except it extended from the visible line.
Leave
space
Leave
space
Correct
No !

8. HIDDEN LINE PRACTICE
Hidden line should intersect to form L and T corners. L T
Correct
No !

9. HIDDEN LINE PRACTICE
Hidden arcs should start on a center line.

10. Using Center Lines Center lines represent axes of symmetry.
They are important for interpreting cylindrical shapes.

11. Using Center Lines
They are also used to indicate circle of centers, and paths of motion.

12. Creating Center Lines Rule 1:
Center lines should start and end with long dashes.

13. Creating Center Lines Rule 2:
Center lines should intersect by crossing either the long dashes or the short dashes.

14. Creating Center Lines Rule 3:
Center lines should extend a short distance beyond the object or feature.

15. Creating Center Lines Rule 4:
Center lines may be connected within a single view to show that two or more features lie in the same plane.
CAUTION! Center lines should not extend through the space between views .

16. CENTER LINE PRACTICE
In circular view, short dash should cross at the intersections of center line.
For small hole, center line is presented as thin continuous line.
Center line should not extend between views.
Leave space
Leave space

17. CENTER LINE PRACTICE
Leave the gap when centerline forms a continuation with a visible or hidden line
Center line should always start and end with
long dash.
Leave space
Leave space
Leave space
Leave space

18. PRECEDENCE OF LINE Order of importance Visible line Hidden line Center

19. Exercise
Fill the following dotted orthographic projection with the appropriate line types.

20. Fill in the visible lines in to top view.

22. Fill in the visible lines in to front view.

24. Fill in the visible lines in to right side view.

26. Fill in the hidden lines in to front, top and right side views.

28. Draw the center lines in all the views.

29. NOTICE!
The small dashes cross in the middle.
NOTICE!
The center line connects between features in the same view.