Page 155 - Engineering drawing from first principles using AutoCAD

148 Enqineerinq drawinq [rom first principles

7
FIRST AUXILIARY
ELEVATION

A B
C1 2 D1
-,
2 3 6 7

4 5 8

-,

SECOND AUXILIARY
PLAN

Figure 6.27

It is sometimes the case that solving projection problems on the small screen can result in
a mass of confusing construction lines. The best advice here is to draw small units one at a
time and remove unnecessary construction lines after the unit is complete. For example,
plot face 5, 6, 7 and 8 and note that opposite sides are parallel to each other. Having
satisfied yourself that this part is accurate, clean up the screen and continue with face 1,
2, 3, and 4. It is often a useful constructional exercise to take a preliminary print on which
you can check, mark up and measure dimensions.

Figure 6.28 shows a cone which has been cut parallel to one side. The auxiliary elevation
is complete and the object of the exercise is to draw the front view and the plan. The
profile of the cut face viewed at right angles in line with arrow X will give a parabola.
Commence the solution by drawing the outlines of the cones. Draw line AA on the
auxiliary view and a circle of diameter AA on the plan. Project lines up to the front