Class: Junior Secondary School 3 (JSS3, JSS 3)
Term: 1st Term
Week: 9
Age: 14 years
Duration: 45 minutes
Subject: Basic Science And Technology
Curriculum Theme: Basic Technology
Previous Lesson: Perspective Drawing and One Point Perspective
Topic: Orthographic Projection
Subject Matter: Definition, Types (1st and 3rd angle), Drawing of Orthographic Views of Simple Objects, Dimension Technique

Specific Objectives

By the end of the lesson, pupils should be able to:

Cognitive Domain:
(a) State the meaning of orthographic projection.
(b) Differentiate between first angle and third angle projections.
(c) Identify the main views used in orthographic projection.
Affective Domain:
(a) Appreciate the importance of neatness and accuracy in technical drawing.
(b) Develop interest in creating correct engineering drawings.
Psychomotor Domain:
(a) Draw simple objects using orthographic projection methods.
(b) Apply dimensioning techniques in drawings correctly.
Social Domain:
(a) Work cooperatively in groups to practice and compare orthographic drawings.

Reference Materials

The following resources was used in planning this lesson:

9 Years Basic Education Curriculum
Lagos State Unified Scheme of Work for Junior Secondary Schools
Wikipedia – Orthographic projection
Relevant Textbooks

Instructional Materials

The teacher will teach this lesson with the aid of:

Drawing instruments (T-square, set squares, pencils, eraser, compass, drawing board)
Charts showing 1st and 3rd angle projection symbols
Models of simple objects (cube, box, cup, or block)
Sample orthographic drawings
Whiteboard and markers

Rationale for the Lesson

This lesson helps students understand how to represent 3-dimensional objects accurately in 2-dimensional views, which is essential in engineering, architecture, and design.

Prerequisite/Previous Knowledge

Pupils are already familiar with basic technical drawing concepts such as plane shapes, simple geometric constructions, and use of drawing tools.

Lesson Content/Board Summary

Orthographic Projection

Orthographic projection is a method of representing a 3-dimensional object on a 2-dimensional surface using different views. It shows the object’s shape and size from several directions such as front, top, and side.

Orthographic projection allows engineers and designers to communicate ideas clearly and precisely in technical drawings.

Types of Orthographic Projection

There are two main types of orthographic projection used in technical drawing. They are:

First Angle Projection:
In this system, the object is placed between the observer and the plane of projection. The views are arranged such that the plan (top view) is below the elevation (front view), and the right-hand side view is placed on the left.
Third Angle Projection:
In this system, the plane of projection is between the observer and the object. The views are arranged such that the plan (top view) is above the elevation (front view), and the right-hand side view is placed on the right.

The following are the differences between first angle and third angle projections:

In first angle projection, the object is between the observer and projection plane; in third angle, the plane is between the observer and the object.
In first angle, the top view is below the front view; in third angle, it is above.
In first angle, the right-side view is drawn on the left; in third angle, it is drawn on the right.
The projection symbol differs for each method.

Drawing of Orthographic Views of Simple Objects

Orthographic drawing involves showing an object using three main views:

Front view (Elevation) – shows the height and width of the object.
Top view (Plan) – shows the length and width.
Side view (End elevation) – shows the height and length.

The following are steps in drawing orthographic views:

Select an appropriate scale for the drawing.
Draw construction lines lightly to guide the views.
Sketch the front, top, and side views based on the given object.
Ensure all views are aligned vertically and horizontally.
Add outlines with thicker lines.
Label the views correctly.

Dimension Technique

Dimensioning is the process of adding measurements to a drawing to show the actual size of the object. It ensures that anyone who reads the drawing can produce the object accurately.

The following are the rules and techniques of dimensioning:

Dimensions should be placed above dimension lines and in clear positions.
Use arrowheads at both ends of dimension lines.
Use thin, continuous lines for dimension lines.
Avoid crowding dimensions.
Show overall and detailed dimensions clearly.
Maintain uniform spacing and size of lettering.

Teaching Methods/Instructional Techniques:

Lecture, Discussion, Demonstration, Explanation, Illustration, Guided Practice, Question and Answer

Instructional Procedures

To deliver this lesson, the teacher will adopt the following steps:

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: Teacher displays simple objects and asks pupils how they can show the shape of the object on paper. Introduces the term “Orthographic Projection.”
Pupils’ Activity: Pupils respond to questions and observe the objects.
Learning Point: Pupils are motivated to learn how objects can be represented in different views.

Step 2: Explanation of Orthographic Projection

Time: 8 minutes
Teaching Skill: Explanation
Teacher’s Activity: The teacher explains the concept of orthographic projection and its purpose in technical drawing.
Pupils’ Activity: Pupils listen and ask questions.
Learning Point: Pupils understand what orthographic projection means.

Step 3: Types of Orthographic Projection

Time: 10 minutes
Teaching Skill: Discussion and Illustration
Teacher’s Activity: The teacher explains first and third angle projections using charts and diagrams.
Pupils’ Activity: Pupils observe, discuss, and compare the two systems.
Learning Point: Pupils can differentiate between first and third angle projections.

Step 4: Drawing of Orthographic Views and Dimension Technique

Time: 15 minutes
Teaching Skill: Demonstration
Teacher’s Activity: The teacher demonstrates drawing of simple orthographic views and how to apply dimensioning correctly.
Pupils’ Activity: Pupils practice drawing using their instruments.
Learning Point: Pupils acquire practical skills in orthographic projection and dimensioning.

Step 5: Note-Taking

Time: 3 minutes
Teaching Skill: Explanation
Teacher’s Activity: The teacher dictates or writes the board summary for pupils to copy.
Pupils’ Activity: Pupils copy the notes.
Learning Point: Pupils record accurate notes on orthographic projection.

Step 6: Evaluation/Review

Time: 3 minutes
Teaching Skill: Questioning
Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

Define orthographic projection.
Mention two types of orthographic projection.
List three differences between first and third angle projection.
What are the three main views in orthographic drawing?
State two rules for dimensioning.
Pupils’ Activity: Pupils respond to the questions orally.
Learning Point: Pupils demonstrate understanding of the lesson.

Step 7: Conclusion

Time: 1 minute
Teaching Skill: Reinforcement
Teacher’s Activity: The teacher summarizes the key points and encourages pupils to practice more drawings.
Pupils’ Activity: Pupils listen attentively.
Learning Point: Pupils understand the importance of accuracy and neatness in orthographic drawing.

Lesson Keywords

Projection – method of showing an object on a flat surface.
Elevation – the front view of an object.
Plan – the top view of an object.
Dimensioning – adding measurements to a drawing.
Angle Projection – method of positioning object and plane in drawing.

Differentiation

Teacher supports slower learners with guided practice and visual aids while advanced learners draw more complex objects independently.

Note for teachers using this lesson plan

Ensure students use proper drawing instruments correctly and maintain neatness. Reinforce alignment of views and accurate dimensioning for clarity.