# Lesson Notes By Weeks and Term - Junior Secondary School 3

SCALES AND SCALE DRAWING, SIMPLE BLUE PRINT READING

TERM: FIRST TERM

SUBJECT: BASIC TECHNOLOGY

CLASS: JSS 3

REF MATERIALS

• EVANS BASIC TECH FOR JSS BOOK 3
• NERDC BASIC TECH FOR JSS BOOK THREE

WEEK ELEVEN

TOPIC: SCALES AND SCALE DRAWING, SIMPLE BLUE PRINT READING

CONTENT

1. DEFINITION OF SCALE DRAWING
2. MATERIALS AND INSTRUMENTS FOR SCALE DRAWING
3. TYPES OF SCALE DRAWING
4. MEASURING AND COMPARING GIVEN SIZES
5. SIMPLE DETAILS OF A BUILDING PLAN
6. COMMON SYMBOLS USED AND THEIR INTERPRETATIONS

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

1. Metric rule

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.

1. Scale rule

These have three straight edges and are triangular in shape. Each edge is graduated and each scale designation is marked on the rule.

EVALUATION

• Define scale drawing.
•  State the materials and instruments for scale drawing.

SCALE

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

Ascale is used to draw or read a scale on a drawing paper

We have the following scales:

1. Full scale  drawing
2. Reduced scale drawing
3. Enlarged scale drawing

Therefore a cupboard of size 1800mm long drawn as 18mm has a reduced scale drawing of 1:100mm.

ENLARGED SCALE 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

REDUCED SCALE DRAWING: this is used when the object to be drawn is too big. Here the actual size of the object is reduced in the proportion of the drawing. Examples include 1:2, 1:5, 1:10, 1: 100 etc.

FULL SCALE DRAWING: This is when the object to be drawn is the same size as the size of the object the scale used is 1:1.

EVALUATION

1. Define scale drawing.
2. Mention three types of scale drawing.

Blueprint is the means of communication between the builders and building designer(architect). They are finished plans of what is to be produced or built,i.e. it is the complete drawings builders use at their building site to build. In building industry, the blueprint is also called the working drawing. The blue print is prepared by the architect while the builder interpretsit correctly. Blue print reading requires high-level knowledge of architectural and engineering drawings. It also requires ability to understand measurements and to measure accurately. Any mistake error could be too costly.

The following are to be interpreted by the builders.

1. The floor plan
2. The elevation
3. The section
4. The detailed drawings
5. The schedule
6. The electrical plan

COMMON SYMBOLS USED AND THEIR INTERPRETATIONS.

 S /N SYMBOLS MEANING 1 Earth or soil 2 Strip foundation 3 Hardcore 4 Mass concrete floor slab 5 Stone work 6 Brickwork 7 Block work 8 Timber 9 Bath 10 Water closet 11 Sink 12 Wash hand basing 13 Fluorescent tube 14 Socket outline 15 Switch 16 Electric meter 17 Window 18 Door 19 Filament bulb

EVALUATION

1. Define simple blue print.
2. Mention five sections that can be find in a blueprint reading
3. Provide symbols for the following: doors, switch, hard core, concretes, wash hand

basing.

GENERAL EVALUATION

1. Define scale.
2. Define scale drawing.
3. Draw the top of your desk using scale rule.
4. Draw a line 80mm and an equivalent of it in cm indicating the dimensions in cm.
5. Produce the building plan of a bungalow on page 235 of NERDC BK3 On a drawing sheet.

REFERENCE MATERIALS:

1. EVANS, BASIC TECHNOLOGY FOR JSS, BOOK 3 pages 97-101.
2. NERDC, BASIC TECHNOLOGY FOR JSS, BOOK 3 pages 220-236.

WEEKEND ASSIGNMENT

1. ________  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.
2. In _____ scale drawing, the object is drawn to the same size with the actual size. e.g.   1:1 A. enlarged  B. reduced C. full D. proportioned.
3. In ______ scale drawing the  actual size of the object is reduced in proportion to the drawing .It is used when the object is too big , examples include 1:2   ,  1:5   ,1:10  , 1:50   ,1:100  A. enlarged  B. reduced C. full D. proportioned.
4. _involves the assembly and erection of building structures. A. Building construction
1. Architectural C. Marine engineering D. Forecasting engineering.
1. The following are the professionals in building industry except____________(a) Architect (b)structural engineer (c) quantity surveyor (d) agricultural engineer

THEORY

1. What do you understand by the word blueprint.
2. Mention types of scale drawing and explain them.