oRTHOGRAPHIC PROJECTION TERMINOLOGIES

1. ORTHOGRAPHIC PROJECTION
An orthographic drawing represents a three-dimensional object using
several two-dimensional views of the object. It is also known as an
orthographic projection. It is a method of representing the exact shape of the
object by dropping two or more views perpendicular to a plane generally at
right angle.
MULTI-VIEW PROJECTION
In industry, a complete and clear description of the shape and size of
an object to be made is necessary to make certain that the object will be
manufactured exactly as intended by the designer. In order to provide this
information clearly and accurately, a number of views, systematically
arranged, are used. This system of views is called multi-view projection.
THE SIX PRINCIPAL VIEWS
1. Top View – it is drawn above the front
2. Front View – it is drawn vertically aligned and below the top view
3. Right Side View – This is located at the right side and aligned with the
front view
4. Left Side View – The opposite of the right side view. It is located at
the left side and aligned with the front view
5. Rear View – The opposite view of the front view. It is located aligned
after either at the right or left side view
6. Bottom view – The opposite of the top view. This must be drawn
vertically aligned and below the front view.
THE THREE REGULAR ORTHOGRAPHIC VIEWS
The following are the three regular views because they are the views
most frequently used. The views should be spaced well apart and yet close
enough to “hang together”. If dimensions are to be added, sufficient space for
them between views will have to be allowed.
1. Top View
2. Front View
3. Side View
PLANES OF PROJECTION
1. Horizontal Plane – the plane upon which the top view is projected
2. Frontal Plane – the plane upon which the front view is projected
3. Profile Plane – the plane upon which the side view is projected
THE THREE PRINCIPAL DIMENSIONS OF AN OBJECT
1. Height – the distance between two horizontal planes
2. Width – the distance between two profile planes
3. Depth – the distance between two frontal planes
THE GLASS BOX
If planes of projection are placed parallel to the principal faces of the
object, they form a “glass box”. The observer is on the outside looking in, so
that he sees the object through the planes of projection. Since the glass box
has six sides, six views of the object are obtained.
THE ALPHABET OF LINES
This is a list of the different lines use in orthographic and pictorial
drawings.
1. Construction line – line used to construct the view of an object
2. Visible Line – also called Object Line. A line that represents the
visible edges of an object
3. Hidden Line – line that represents the hidden edges of an object
4. Projection Line – lines used to project one view to another
5. Center Line – line used to show the centers of holes or circular
objects
6. Dimension line – line used to show the size of an object, spans from
one extension line to the next, has arrowheads on both ends and is
broken in the middle for the measurement number
7. Extension line – line that indicates the limit of a dimension line
8. Leader Line – line used to direct descriptive major information, notes
or special dimensions to feature on the drawing.
9. Reference Line – line used for indicating the name of the part of an
object
10. Cutting Plane Line – line used for cutting objects in the drawing,
locate plane of projection for section or cut away views.
11. Section Lines – lines to show a surface that has been cut in a
sectional view. The surface indicated with section line is presumed to
be solid portion.
12. Short Break Line – used for limiting the length of narrow elongated
object
13. Long Break Line – used for limiting the length of wide elongated
object.
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