Technical Drawing · Lesson 1

Drawing instruments, paper sizes, lines, lettering, title blocks, dimensioning and sketching

WAECNECO

What the syllabus asks

WAEC: WAEC/NECO Technical Drawing, Plane Geometry items 1 (materials and equipment, types of drawing, A2 board and sheet) and 2 (types of lines, lettering, title blocks, borders, dimensioning to BS 308/BS 1192, now BS 8888/ISO), Solid Geometry item 19 (symbols and conventions, e.g. ⌀), Paper 3 Section A (freehand sketching); Mechanical item 2 (dimensioning techniques). (Not a JAMB UTME subject:…

NECO: WAEC/NECO Technical Drawing, Plane Geometry items 1 (materials and equipment, types of drawing, A2 board and sheet) and 2 (types of lines, lettering, title blocks, borders, dimensioning to BS 308/BS 1192, now BS 8888/ISO), Solid Geometry item 19 (symbols and conventions, e.g. ⌀), Paper 3 Section A (freehand sketching); Mechanical item 2 (dimensioning techniques). (Not a JAMB UTME subject:…

What you will learn

Explain what technical drawing is and name the main types of drawing and their uses.
Identify, use and care for drawing instruments and materials.
State the ISO A-series paper sizes and lay out a sheet with border and title block.
Draw and use each type of line correctly, with the order of precedence.
Letter neatly in single-stroke capitals of standard heights.
Use scales of reduction and enlargement.
Dimension drawings correctly using standard rules, methods and symbols.
Make clear freehand sketches of tools and components.

Key points

Technical drawing is a precise, standard-based graphic language.
Know drawing types: sketch, pictorial, orthographic, detail, assembly, building, development.
T-square for horizontals; set squares for 30°, 45°, 60°, 90° and with both squares every 15°.
2H for construction, HB for outlines; compasses use chisel points.
A0 = 841 × 1189 (1 m²); each size halves; A2 = 420 × 594; sides 1 : √2.
Border plus title block bottom right: title, scale, projection, units, name, date.
Thick continuous = visible; thin continuous = dimensions/hatching; dashed = hidden; chain = centre; chain thick ends = cutting plane.
Precedence: visible, hidden, cutting plane, centre line.
Lettering: single-stroke capitals between guidelines, uniform heights.
Scale = drawing : true; dimensions always show true size.
Dimension rules: once only, outside the view, not to hidden lines, ⌀ for circles, R for arcs, locate holes from centres.
Freehand sketches: proportion first, light box, then detail; label parts.

Start here: What technical drawing is

Technical drawing (also called engineering or graphic communication) is the exact, rule-governed drawing of objects so that someone else can make, build or check them without asking questions. A novel uses words to tell a story; a technical drawing uses lines, symbols, dimensions and notes to describe shape, size, material and finish. A welder in Nnewi, a carpenter in Ibadan and an engineer in Kano who have never met can all read the same drawing because they follow the same conventions (agreed rules), set out in national and international standards.

Why it matters

It is a universal language: shapes and symbols cross language barriers.
It is precise: a sketch says “about this big”; a working drawing says “80 mm ± 0.1”.
It is a legal and contractual record: builders, clients and inspectors refer back to the approved drawings.
It trains spatial thinking: seeing a three-dimensional object from flat views and the reverse, a skill used in engineering, architecture, surveying, medicine (reading scans) and design.

Types of drawing and their applications

Type	What it shows	Typical user
Freehand sketch	Quick idea drawn without instruments, roughly in proportion	Designer on site, exam Paper 3 Section A
Pictorial drawing (isometric, oblique, perspective)	One 3-D looking view	Catalogues, assembly instructions, clients
Orthographic (multi-view) drawing	Several flat views (front, plan, end) at true size or to scale	Manufacturers, builders
Detail (component) drawing	One part, fully dimensioned, with material and finish	Machinist, fabricator
Assembly / general arrangement drawing	How parts fit together, with a parts list	Fitters, maintenance staff
Building (architectural) drawings	Site plan, floor plans, elevations, sections, details	Builders, town-planning approval
Development (pattern) drawing	A flat pattern that folds into a 3-D shape	Tinsmiths, sheet-metal and packaging firms

The WAEC syllabus divides the subject into plane geometry (flat constructions), solid geometry (projections of 3-D objects) and one of two options, Building Drawing or Mechanical Drawing. This first unit gives you the tools and the “grammar” that every other unit uses.

Manual drawing and CAD

Industry now produces most drawings with computer-aided design (CAD) software, but the rules are the same: line types, projection, dimensioning and scales. Examiners still test manual skill because a person who can construct a tangent by hand understands what the software is doing. Treat your instruments as you would a stethoscope or a spanner: a professional tool that rewards care.

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Practice questions

1. The size of an A2 drawing sheet is

420 × 594 mm
297 × 420 mm
594 × 841 mm
841 × 1189 mm

Show answer

A: 420 × 594 mm
A2 is A0 halved twice: 420 × 594 mm.

2. An A0 sheet has an area of about

0.5 m²
2 m²
0.25 m²
1 m²

Show answer

D: 1 m²
841 × 1189 mm ≈ 1 m².

3. Halving an A3 sheet across its long side gives

Show answer

C: A4
Each smaller A size is half the one above.

4. The instrument used with a T-square to draw lines at 30°, 45° and 60° is the

dividers
set square
protractor
French curve

Show answer

B: set square
Set squares give fixed angles quickly.

5. Hidden edges are drawn with

thin dashed lines
thick continuous lines
thin chain lines
thick chain lines

Show answer

A: thin dashed lines
A dashed line shows an edge you cannot see.

Key words

Convention: An agreed way of representing something on a drawing.
Standard: A published set of rules, e.g. BS 8888, ISO 128.
T-square: Straight edge with a stock, used for horizontal lines.
Set square: Triangle (45° or 30°/60°) used with a T-square.
Dividers: Two-pointed instrument for transferring lengths.
Construction line: Very faint line used while building a drawing.
Outline: Thick continuous line showing a visible edge.
Hidden line: Thin dashed line showing an unseen edge.
Centre line: Thin chain line marking an axis or centre.
Cutting plane: Chain line, thick at ends, showing where a section is taken.
Hatching: Thin lines (usually 45°) showing a cut surface.
Title block: Box giving title, scale, projection, name and date.

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