SUBJECT : BASIC TECHNOLOGY
CLASS : JSS 3
TOPIC : DRAWING PRACTICES (PICTORIAL DRAWING)
The pictorial drawings and orthographic drawings are the two broad classes of the technical drawings. The pictorial drawings is the method of drawing solid objects which show the three dimensional views (i.e. length, width and height) of an object in one view.
The pictorial drawing is grouped into three:
1) The isometric drawing
2) The oblique drawing
3) The perspective drawing
1) THE ISOMETRIC DRAWING
The principal distinguishing features of an isometric drawing are the lines on which the drawing is built. These lines which are known as isometric axes are inclined at an angle 120° to one another.
There are three (3) isometric axis one of them is vertical, the other two receding axes are appositely inclined at an angle of 30° to the Horizontal. They may be constructed with the use of a T-square and 60°/30° set squares.
The isometric drawing is the pictorial method of drawing an object in which all the isometric axes are projected at an angle 30° to the horizontal plane. The Isometric Drawings show the three axes of an object i.e.
a) The Length.
b) The Width.
c) The Height.
CONSTRUCTION OF ISOMETRIC DRAWING.
The practical steps in drawing isometric views involve three main stages:
1)Drawing of the isometric axes.
2)Drawing of the isometric box.
3)Shaping of the box into the required shape and the outlining of the edges.
Procedures/Steps:
Step I: Set your paper on the drawing board, using cello tape.
Step II: Draw the boarder line (10mm=1cm) from the margin.
Step III: Draw the title block, supported by the use of T-squares.
Step IV: Remove the set square and draw the base of the vertical line (a short continuous line).
Step V: Consider the block object of a given length (L), Breadth (B) and Height (H).
Step VI: Measure the length (L) along OA on the receding axes. Measure the breadth (B) along OC on the receding axes.
Step VII: Then draw the isometric box.
Step VIII: Draw the correct shape of the object with thick continuous line (i.e outline.)
ASSIGNMENT:
1) Define Pictorial drawing.
2) Explain Isometric drawing.
3) List the three axes of isometric drawings.