SUBJECT: BASIC TECHNOLOGY
CLASS : JSS 3
TOPIC: TECHNICAL DRAWING 1
SUB-TOPIC : PICTORIAL DRAWINGS
Pictorial drawings are three-dimensional drawings.
Pictorial drawings, as the name implies, show the picture of how an object, tools, machines or machine parts look like when three faces of such structural solid are shown.
Pictorial drawings include Isometric Drawing, Oblique Drawing, Perspective Drawing and Axonometric Drawing.
Three parameters are usually required in pictorial drawings – the length, the height and the width of the object to be drawn.
We shall be limiting the scope of this lesson to Isometric and Oblique Drawings.
ISOMETRIC DRAWING Isometric drawing is a geometry connected with a style of drawings in three dimensions.
It is a method of producing a pictorial view of an object, that is, a view which shows three faces of the object simultaneously.
ISOMETRIC AXES Drawings are built upon isometic axes and any line parallel to the axes are called isometric lines. The common practice is drawing all isometric lines at angle of 30
HOW TO MAKE ISOMETRIC DRAWING OF SOLIDS
In making the drawing of a solid in isometric, say a cuboid for example, the following steps can be taken:
1. Start with the three axes (in this case, I represent the axes as AB, AE and AD) at angle of 30 2. Mark off required dimensions on length AB, width AE and height AD.
3. Draw vertical lines at points B and E.
4. Draw lines from point D parallel to AB and AE for corners C and H.
5. Draw a line from point H parallel to DC and another from point C parallel to DH to complete the isometric drawing.
In oblique projection, the front view of an object is drawn true to dimensions as the represented face in the elevation, all other faces of the receeding lines are drawn at an angle( either 30°, 45° or 60°, though 30°or 45° is usually the common practice).
We have two types of Oblique Drawing, viz Cavalier Oblique Drawing and Cabinet Oblique Drawing.
In cavalier drawing, all sides are drawn to true lengths while in cabinet drawing, the receeding length is shortened to a certain ratio of the actual length.
HOW TO MAKE OBLIQUE DRAWING
EXAMPLES OF OBLIQUE DRAWINGS