1. Mechanical Engineering Drawing MECH 211/M
Lecture #1 Chapters 1 and 6
Dr. John Cheung

2. What makes a good technical drawing?
Should represent the concept/object clearly
Does not cause any uncertainty about the details
Drawn in a way that reduces complexity of the drawing
Complies with standards
Neat and clean
Provides all information needed
Well organized on the paper

3. Common Parallel Projection Types
Oblique Projection Isometric projection Multi-view Projection

4. First vs. Third Angle Projection
First Angle Projection (Europe except UK)
Third Angle Projection

5. Multiview Projection

6. Object Orientation

7. Techniques for Transferring Dimensions
Faster and more accurate for advanced students
Good for beginners

8. How to Transfer Points Using Miter Line

9. How to Transfer Points Using Miter Line

10. How to Transfer Points Using Miter Line
Folding lines needed in the drawing.

11. Surfaces
A surface that is perpendicular to the plane of projection it is seen as ...? (surface, edge view (as a line), point)
A surface that is parallel to the plane of projection (Normal Surface) it is seen as ...? (true size, foreshortened) (surface, edge, point)
A surface that is at an angle to the plane of projection (Oblique Surface) it is seen as ...? (true size, foreshortened) (surface, edge, point)

12. Normal Surface and Edge
Example:
Normal Surface: A plane surface that is parallel to a plane of projection. E.g. Plane A // to horizontal projection plane.
Horizontal projection plane
Plane A
Profile plane of projection

13. Inclined Surface and Edge
Inclined Surface: A plane surface that is perpendicular to one plane of projection but inclined to adjacent planes. Surface A perp. to horizontal projection plane – TL line 3-5.
Line 7-8 parallel to horizontal folding line, hence true length in top view.

14. Oblique Surface and Edge
Oblique Surface: A plane that is oblique to all planes of projection (not // to any plane, hence no true size), Surface C in top view.
True size – rotating or draw secondary auxiliary view – Line // to folding line – true length – edge view – true shape.

15. Applications - True Length Lines
To draw a true length line:
When foreshortened - use a fold-line parallel to the line of interest.
When viewed as a point - draw any view perpendicular to it
When line is fully in a plane – it is true length.

16. Applications - Surfaces in Edge View
To draw a surface as an edge view:
Choose an edge and draw it so that it is a true length.
Draw a view that is perpendicular to that true length line to get an edge view.

17. Applications - True Shape of a Surface
To determine the true shape and size of a surface:
Draw the surface as an edge view
Draw a view that is perpendicular to the edge view
A surface that is parallel to the view plane is true shape
All of the lines in the plane are true size
Planes that are orthogonal to this plane are true

18. Oblique Surface – True Shape

19. Oblique Surface – True Shape

20. Dihedral Angle
T.L. Line 1-2
Dim. D from front view
Point view 1 & 2.

21. Example - Line perpendicular to edge view

22. Dihedral Angle Example

23. Summary Any comments or Questions
Orthogonal projection – Multi-view projection.
Third angle projection.
Folding lines.
Transferring data using dividers or Miter line.
Line parallel to folding line.
True length (length of part).
Edge view.
True shape (size) – (surface area).
Dihedral angle.
Any comments or Questions