CLASSIFICATION OF SURFACES
Horizontal, frontal and profile surfaces are those which are parallel to the horizontal,
frontal and profile planes o-f projection and these will be represented by their actual size
in the respective views but are shown just by lines in the other views. Auxiliary or inclined surface is inclined to two of the planes of projection but is perpendicular to the third.
The inclined surface will appear as an inclined edge in the view for which it is parallel to
the plane of projection, while, in the other views, it will be shown by reduced
dimensions. A surface inclined to all the three planes of projection is termed oblique or
skew surface and is shown by reduced dimensions and inclined lines in all the views.
Curves perpendicular to the picture planes will be shown by rectangles because
actually the curves move out of the paper or into the paper. Sometimes very light
lines at
Fig. 3.6 Types of Surface (Part A-G)
varying spacing are used to indicate these types of curves. Spacing of the lines is
made greater in the portion where the curve appears to be relatively flat and then the
spacing is decreased as the slope of the curve appears to increase from that
particular view direction. These lines are used only as a background symbol and must be drawn so light that they do not interfere with dashed and center lines present in that portion. Curves parallel to the picture plane are shown by lines having the actual
curvature.
