SECOND TERM E-LEARNING NOTE
SUBJECT: BASIC TECHNOLOGY
CLASS: JSS 1
WEEK FIVE AND SIX Date:……………………………
TOPIC: FREEHAND SKETCHING
DEFINTION OF FREEHAND SKETCHING
Freehand Sketching is one of the quickest methods by which the shape of an object can be communicated to others. This is done by using a pen or pencil.
Architects think more of imaginary objects; they cannot take photographs but express this using freehand sketching.
Therefore, the knowledge of freehand sketching is of advantage. A good sketch reduces the task of writing needed to describe the object on the mind of the designer. The ability to make a freehand sketching is a valuable asset acquired through practice.
SKETCHING A STRAIGHT LINE
A straight line can be defined as the shortest distance between two points.
Straight line can be sketched following the procedures below:
SKETCHING: A CURVE AND CIRCLE
With the points in position, attempt to draw curves to join them.
SKETCHING: A SQUARE AND AN IRREGULAR EDGE
This can be sketched in isometric or oblique view.Isometric view is at 300 to the horizontal the at both sides .Oblique view is at 450 to the horizontal at one side
DEFINITION OF SCALE DRAWING
Scale drawing can be defined as the accurate representation of objects in a determined proportion.Scale drawing is different from ordinary drawing in that it presents the object either reduced or enlarged. There are scales for reduction and for enlargement of the size of the object.
MATERIALS AND INSTRUMENTS FOR SCALE DRAWING
This has two flat straight edges. It is usually 30cm long. Each main division on the metric rule is equal to one centimeter (1cm =10mm) and each division is sub divided into 10 units being 1mm.Always start from 0 as the beginning of your measurement.
These have three straight edges and are triangular in shape. Each edge is graduated and each scale designation is marked on the rule.
Some objects are too big for the actual size to be contained on a drawing paper, while some are too small for the parts to be clearly seen. Hence, such objects should be drawn to an appropriate scale.
Scale is usually given as a ratio and they are stated in the title block.
TYPES OF SCALE DRAWING
A scale is used to draw or read a scale on a drawing paper
We have the following scales:
FULL SCALE DRAWING
In this scale drawing, the object is drawn to the same size with the actual size. e.g. 1:1
REDUCED SCALE DRAWING
The actual size of the object is reduced in proportion to the drawing. Reduced scale drawing is used when the object is too big, examples include 1:2 , 1:5 ,1:10 , 1:50 ,1:100
Therefore a cupboard of size 1800mm long drawn as 18mm has a reduced scale drawing of 1:100mm
ENLARGED SCLAE DRAWING
This is used when the object to be drawn is too small to be clearly seen .Here, the actual size of the object is enlarged in the proportion to the drawing.
Examples include 2:1, 10:1, 100:1,
Drawing size 100:1 actual size
Read on Scale Drawing from Introductory Technology (JSS1) by Evans. Pages 19-20
work. (c) Laypersons can express themselves by freehand sketches. (d) Materials are wasted by freehand sketches.
6.________ can be defined as the accurate representation of objects in a determined proportion (a) Scale drawing (b) Freehand sketches (c) Technical drawing (d) Isometric drawing
(b) drawing size (c) proportioned (d) regular
10._____ scale drawing is used when the object to be drawn is too small to be clearly seen (a) Enlarged (b) Reduced (c) Full (d) Proportioned
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