1. Axonometric drawings
BDU 10303

2. 2D Drawing Types Pictoral drawing Multiview drawing
Drawing that show 3 principal faces of the object in one view
Example:
Axonometric drawings
Isometric
Dimetric
Trimetric
Oblique drawings
Multiview drawing
Shows only two dimensions in each view
Orthographic drawing

3. Isometric drawing
Isometric drawing present the pictorial view of an object.
More easy to understand than orthographic projection.
Is an application of the orthographic projection.

4. Conventional Isometric Projection
Note that there are three isometric axes. These are inclined at 120° to each other. One axis is vertical and the other two axes are therefore at 30° to the horizontal.
The faces of the shaped block are all at 90° to each other. The lines in the isometric drawing are parallel to the isometric axes. For example...
If the lines are not parallel to any of the isometric axes, they are no longer true lengths.

5. Isometric projection
Isometric projection is a true representation of the isometric view of an object
Isometric view is created by rotating the object 45 deg about vertical axes and tilting forward about 16’.

6. Selection of Isometric Axes
Main purpose of isometric view is to provide pictorial view which reveals as much detail as possible.
Selection of principal edges is important

7. Isometric projection : scale
The tilt causes the edge & planes to become foreshortened.
The projected length is approximately 80% of the true length.

8. Isometric projection & drawing
To avoid difficulty in determining foreshortened length, we can draw isometric projection directly by using true length!
However the drawing will be larger than the actual size (22.5% larger)
Isometric projection
Isometric drawing

9. Iso-circles and arcs
Isometric circles or iso-circle cannot be simply drawn using compass.
Any iso-circle may lie on either top plane, left (front) plane or right (profile) plane.
Iso-circle looks slightly oval and skewed.

10. Drawing Iso-circles Draw centre lines, vertical & 30deg to left.
Draw (construction line) “square box”. The centre lines should divide each side by half.
Draw straight lines; 1-2 & 1-3 and 2-5 & 2-6.
Point 7 is the intersection between line 1-2 & 4-5, and similarly point 8, 1-3 & 4-6 on the other side.
Set your compass to the distance 7-2, draw an arc with centre at point 7, from point 2 to point 5. Do the same on the other side.
Set your compass to the distance 1-2, draw an arc with centre (1), from 2 to 3.

11. Irregular curves
Irregular curves in isometric are produced by transferring the coordinates from orthogonal view.
A fixed distance is set, A, and the distance in B direction are obtained.
These values are then transferred to the isometric view.

12. Producing Isometric drawing
Start to draw when you are able to visualize the objects.
Start with construction lines:
Draw the iso-box
Filled the box with lines
Darken the lines, arcs and circles related to the object.

13. Axonometric Projection
Steps in Making an Isometric Drawing
Draw the enclosing box using the overall dimensions of the object with construction lines.
Block in the various shapes and details using construction lines.
Darken in all final lines.

14. Assignment 3
Draw, full size, an isometric projection of the component shown in following figure looking in the direction of the arrow A