# BASIC TECHNOLOGY JS3

SUBJECT:  BASIC TECHNOLOGY

CLASS : JSS 3

TOPIC:                    TECHNICAL DRAWING 1

SUB-TOPIC :                PICTORIAL DRAWINGS

CONTENT :

INTRODUCTION

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.

EXERCISES

OBLIQUE 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.

OBLIQUE AXES

HOW  TO MAKE OBLIQUE DRAWING

EXAMPLES OF OBLIQUE DRAWINGS