5.3.2. Isometric Drawing
When a drawing is prepared with an isometric scale or other
wise as the object is actually projected on a plane of
projection, it is an isometric projection. But when it is prepared
with an ordinary scale, it is an isometric drawing. The
isometric drawing is 22.5% larger than the isometric
projection, but the pictorial value is obviously the same in
both.
Since the isometric projection is foreshortened and an
isometric drawing is full size, it is customary to make an
isometric drawing rather than an isometric projection, because
it is so much easier to execute and, for all practical purposes,
is just as satisfactory as the isometric projection.
The steps in constructing an isometric drawing of an object
composed only of normal surfaces, as illustrated in figure 5.20
.Notice that all measurements are made parallel to the main
edges of enclosing box, that is, parallel to isometric axes. No
measurement along a diagonal (non-isometric line) on any
surface or through the object can be set off directly with the
scale. The object may be drawn in the same position by
beginning at the corner Y or any other corner, instead of at the
corner X.