TECHNICAL DRAWING LESSON NOTE FOR WEEK SIX ENDING 25TH OCT.
, 2024
Date: 21st – 25th October, 2024
CLASS: Year 11
SUBJECT: Technical Drawing
TOPIC: ORTHOGRAPHIC DRAWING
PERIOD: 1
DURATION: 45mins
INSTRUCTIONAL MATERIALS: drawing board, mathematical set.
TEACHING STRATEGY: Practical method
RECOMMENDED TEXT: J.N. Green, Technical Drawing for School Certificate and G.C.E.
REFERENCE BOOK: J.N. Green, Technical Drawing Manual for School Certificate and G.C.E.
BEHAVIOURAL OBJECTIVES: At the end of this lesson, the students should be able to;
1. define orthographic drawing;
2. state characteristics orthographic drawing.
ENTRY BEHAVIOUR: The students have seen some buildings in the environment.
PRESENTATIONS:
Step 1: Teacher gives the students the following pre-test;
What is an Oblique drawing?
Step 2: Teacher revises meaning of Oblique drawing.
Step 3: The teacher introduces the new lesson.
Step 4: Teacher further discusses the topic with the student.
CONTENT
ORTHOGRAPHIC DRAWING
The draughtsman or engineer uses two basic methods to represent an object on paper, board, or
similar surfaces. The two basic methods are:
Orthographic projection
Pictorial projection
Orthographic projection is used to show at least three views. The three views usually shown in
orthographic projection are: front view (elevation), side view (either right side or left side), and plan
(top view). Orthographic drawing is the method of producing the drawing of an object so it can be
fabricated accurately.
CHARACTERISTICS OF ORTHOGRAPHIC DRAWING
1. Standardize lines are used
2. The plan, front and side views of the object are properly drawn
3. Objects are drawn to scale
IMPORTANCE OF ORTHOGRAPHIC DRAWING
1. It shows accurately the shape of the object
2. It shows clearly the size of each part of the object
Dimension of an orthographic drawing is usually measured in millimeters
Step 5: The teacher allows the students to ask questions and the students were given practical works
to do
Step 6: The teacher summarizes the lesson.
EVALUATION:
1. Define orthographic drawing
2. State characteristics orthographic drawing
ASSIGNMENT:
Explain the methods of projection of orthographic drawings.
TOPIC: ORTHOGRAPHIC DRAWING
SUB-TOPIC: METHODS OF PROJECTION
PERIOD: 2
TEACHING STRATEGY: Practical method
DURATION: 45mins
INSTRUCTIONAL MATERIALS: drawing sheet, mathematical set, table.
BEHAVIOURAL OBJECTIVES: At the end of this lesson, the students should be able to;
1. explain the two types of angle of projection;
2. define dimensioning;
3. differentiate between the angles of projection with the aid of a sketch.
ENTRY BEHAVIOUR: The students have previously learnt how to use the compass.
PRESENTATION
Step 1: Teacher gives the students the following pre-test;
What are the types of oblique drawing?
Step 2: Teacher revises Oblique drawing.
Step 3: The teacher introduces the new topic.
Step 4: Teacher demonstrates how to construct arcs and circles to Oblique drawings.
CONTENT
METHODS OF PROJECTION
Orthographic views of objects are drawn on surfaces called planes. A projection plane can be likened
to a screen on which a film is projected. If the screen is placed vertically, the plane is called a vertical
plane. If it is placed horizontally, it is called a horizontal plane. It is equally called a side vertical
plane, if it is placed by either the right hand side or the left hand side.
The method of projection varies depending on the rays of light the object is taken to the plane. When
the projection rays are perpendicular to the plane, the projective method is called ORTHOGRAPHIC.
If the rays are at right angle to the plane, the projection is called OBLIQUE. If the rays are taken to a
particular station, the projective method will result PERSPECTIVE,thereby presenting the object as
would appear to the eye.
ANGLES OF PROJECTION
The angle of projection in common use areof two types namely:
1. First angle projection
2. Third angle projection
The first angle projection method is mainly used in European countries. In this projection, the
front elevation drawing is followed by the plan elevation
The third angle projection method is mainly used in USA and Canada. In this projection, the plan
elevation is followed by front elevation.
There are three types of views in orthographic drawing:
1. Horizontal plan views
2. Vertical plan views
3. Side plan views
DIMENSIONING
This is act of using lines to indicate the length and breadth of a particular object. Lines indicating
extremes of dimension are drawn where required either to the right side or below it.
Step 5: The teacher allows the students to ask their questions.
Step 6: The teacher summarizes the lesson.
EVALUATION:
1. Explain the two types of angle of projection .
2. Define dimensioning.
3. Differentiate between the angles of projection with the aid of a sketch.
ASSIGNMENT:
Explain orthographic projection
