1. Orthographic Projection: an introduction
What is Orthographic
Projection?

2. By the end of the lesson:
Orthographic Projection
Lesson Objectives
By the end of the lesson:
Everyone will be able to produce a simple 3rd Angle Orthographic drawing .
Most will be able to identify the 3rd Angle Orthographic.
Some will understand hidden detail lines and their use.

3. But what does this look like?
Orthographic Projection
Third Angle Orthographic Projection is the most common method of producing a working drawing, made by creating at least three separate 2D views of an object:
Front view
Plan view (above or birds-eye)
End or side view
But what does this look like?

4. Like this.. See it’s easy, now your turn. No? Too complex?
Orthographic Projection
Like this..
See it’s easy, now your turn. No? Too complex?

5. Let me explain… Orthographic Projection
Imagine you are viewing an object in a glass box, like this TV for example.

6. Let me explain… Orthographic Projection
If you view the TV from this angle, what would you see?

7. Let me explain… Orthographic Projection
This is what you would see and this is the FRONT VIEW.

8. Orthographic Projection
Now view the TV from this angle, what would you see? The PLAN or BIRDS EYE VIEW.

9. Orthographic Projection
And finally view the TV from this angle, what would you see? The END or SIDE VIEW.

10. Orthographic Projection
Now imagine you could open up the glass box and see all three images in the exact 2D format and scale you have been looking at each one.

11. Orthographic Projection
Now imagine you could open up the glass box and see all three images in the 2D format and scale you have been looking at each one.
You would have all three 2D drawings on a single plane or surface, creating a THIRD ANGLE ORTHOGRAPHIC DRAWING This is what you would see.

12. Orthographic Projection
Now look at this example using a set of steps, I have included the dimensions on the ISOMETRIC DRAWING.
Plan View (Top)
Front View
End View (Side)
Front View

13. Orthographic Projection
Now look at this example using a set of steps, I have included the dimensions on the ISOMETRIC DRAWING.
Plan View (Top)
End View (Side)
Front View
Note how the three drawings are laid out, all in line with each other and each has been drawn to scale.

14. Orthographic Projection
Now look at this example using a set of steps, I have included the dimensions on the ISOMETRIC DRAWING.
Plan View (Top)
All of this means the drawing meets the required standard and should have the symbol for 3RD ANGLE ORTHOGRAPHIC
PROJECTION.
End View (Side)
Front View
Note how the three drawings are laid out, all in line with each other and each has been drawn to scale.

15. Orthographic Projection
It is showing that we project our images to the right of the plan
This is the symbol for Third Angle Projection drawings and you need to remember it.

16. Orthographic Projection
Now it’s your turn. In your books go to a new page and in a landscape format sketch freehand the shape shown below in the top right hand corner of your page. You have three minutes.

17. Orthographic Projection
Now using your knowledge create a Third Angle Orthographic Projection drawing of the object, the arrow indicates the front view and again this should be done freehand. You have five minutes to complete the work.
Plan View
Front View
End View

18. Orthographic Projection
So how did you do? Does your drawing look like the one below? Do the three 2D drawings line up correctly? Have you created a Third Angle Orthographic Projection? Did anyone draw the hidden detail line?
Plan View
Front View
End View

19. Orthographic Projection
On a Third Angle Orthographic Projection there may often be hidden details, this is shown with a dotted line and indicates where features of an object are that can not be seen in a particular 2D view but which are important when manufacturing the object.

20. Orthographic Projection
On a Third Angle Orthographic Projection there may often be hidden details, this is shown with a dotted line and indicates where features of an object are that can not be seen in a particular 2D view but which are important when manufacturing the object.
The recess shown in the isometric drawing can only be seen in the plan and side view but not in the front view.

21. Orthographic Projection
On a Third Angle Orthographic Projection there may often be hidden details, this is shown with a dotted line and indicates where features of an object are that can not be seen in a particular 2D view but which are important when manufacturing the object.
The recess shown in the isometric drawing can only be seen in the plan and side view but not in the front view.
This hidden detail is always shown and
is done so using a dotted line in the correct location.

22. Orthographic Projection
Now using your knowledge, create a third angle orthographic projection drawing of the object you have been given.
And this time you will draw the object to scale using grid paper and a ruler.
Please note the front view.
Front View
You have ten minutes to complete the drawing.

23. Orthographic Projection
So how did you do? Are all the dimensions correct? Have you included all the hidden detail?

24. Orthographic Projection
Now lets make things a little harder, you have been given a new object to draw.
Please note the diameter of the hole is 10mm and it is centrally located.
You have 10 minutes to complete this drawing.
Front View

25. Orthographic Projection
So how well did you do this time? Are all the dimensions correct again? Have you included all the hidden detail this time? Is the hole the right diameter?

26. Orthographic Projection
Have you achieved the main learning objective? Are there any questions?