Orthographic and isometric - Introduction to AutoCAD 2011: 2D and 3D Design - page 152

Orthographic projection

Orthographic projection involves viewing an article being described in a
technical drawing from different directions - from the front, from a side,
from above, from below or from any other viewing position. Orthographic
projection often involves:
The drawing of details which are hidden, using hidden detail lines.
Sectional views in which the article being drawn is imagined as being cut
through and the cut surface drawn.
Centre lines through arcs, circles spheres and cylindrical shapes.

An example of an orthographic projection

Taking the solid shown in Fig. 7.1 - to construct a three-view orthographic
projection of the solid:
1. Draw what is seen when the solid is viewed from its left-hand side and
regard this as the front of the solid. What is drawn will be a front view
( Fig. 7.2 ).

60

R20

R10

Fig. 7.1 Example -
orthographic
projection - the solid
being drawn

Ø120

Ø60

Ø40

Fig. 7.2 The front view of the solid

2. Draw what is seen when the solid is viewed from the left-hand end of
the front view. This produces an end view . Fig. 7.3 shows the end view
alongside the front view.
3. Draw what is seen when the solid is viewed from above the front view.
This produces a plan . Fig. 7.4 shows the plan below the front view.
4. In the Home/Layers panel in the Layer list click on Centre to make it
the current layer (Fig. 7.5). All lines will now be drawn as centre lines.