Class: Senior Secondary School 1 (SSS 1)
Term: 3rd Term
Week: 12
Age: 15 years
Duration: 45 minutes
Subject: Carpentry And Joinery
Curriculum Theme: Entrepreneurship Trade Subjects
Previous Lesson: Abrading Tools and Abrasives.
Topic: ABRASIVES – Types of Abrasives
Subject Matter: types of abrasives, selection of abrasives, uses of different abrasive grades

Specific Objectives

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

Cognitive Domain:

Define abrasives.
List different types of abrasives.
Explain the criteria for selecting abrasives.
State the uses of different abrasive grades.

Affective Domain:

Appreciate the importance of selecting the correct abrasive for a specific task.
Develop an interest in using abrasives safely and effectively.

Psychomotor Domain:

Identify various types of abrasives.
Demonstrate the proper use of different abrasive grades on materials.

Participate actively in discussions about abrasive selection and use.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Carpentry And Joinery.
State Unified Scheme of Work for Carpentry And Joinery.
Basic Carpentry and Joinery for Senior Secondary Schools by a relevant author/publisher.

Instructional Materials

The teacher will teach this lesson with the aid of:

Various abrasives (e.g., sandpaper of different grits, emery cloth, grinding stones, sanding blocks).
Samples of wood or metal showing different finishes achieved with abrasives.

Rationale for the Lesson

This lesson helps pupils understand the different materials used for smoothing, shaping, and finishing surfaces. Knowing how to select and use abrasives correctly is important for achieving quality finishes in carpentry, joinery, and other practical tasks, which is a key skill in entrepreneurship.

Prerequisite/Previous Knowledge

Pupils should have basic knowledge of common carpentry tools and materials used in woodworking.

Lesson Content/Board Summary

ABRASIVES – Types of Abrasives

Definition of Abrasives

Abrasives are hard materials used for grinding, polishing, smoothing, or cleaning other harder surfaces by rubbing.

Types of Abrasives

Abrasives can be broadly categorized into natural and synthetic types:

**Natural Abrasives:** These are found naturally and include materials like garnet, flint, pumice, and emery.
**Synthetic Abrasives:** These are manufactured and include materials like aluminium oxide, silicon carbide, zirconia alumina, and ceramic alumina.

Selection of Abrasives

The following factors should be considered when selecting abrasives:

**Type of Material:** Different materials (wood, metal, plastic) require specific types of abrasives.
**Desired Finish:** The level of smoothness or roughness required for the final product.
**Speed of Cutting/Grinding:** Some abrasives cut faster than others.
**Cost:** The economic factor in choosing abrasives.
**Durability:** The lifespan of the abrasive material.

Uses of Different Abrasive Grades (Grit Sizes)

Abrasives are graded by grit size, which indicates the coarseness of the abrasive particles. The following are common grades and their uses:

**Coarse Grit (e.g., 40-80 grit):** Used for rapid material removal, shaping, and removing old paint or heavy rust.
**Medium Grit (e.g., 100-150 grit):** Used for general sanding, smoothing rough surfaces, and preparing for finer grits.
**Fine Grit (e.g., 180-220 grit):** Used for final sanding before finishing, removing minor imperfections, and smoothing wood.
**Very Fine Grit (e.g., 240 grit and higher):** Used for sanding between coats of finish, light sanding of delicate materials, and achieving a very smooth finish.

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher greets the pupils, reviews the previous lesson briefly, and then introduces the new topic by showing various samples of abrasives (e.g., different types of sandpaper) and asking pupils about their uses in carpentry or at home.
Pupils’ Activity: Pupils respond to questions, observe the materials, and recall previous knowledge.
Learning Point: Pupils are engaged and prepared for the new lesson, linking it to practical experiences.

Step 2: Definition of Abrasives

Time: 5 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher clearly defines what abrasives are, explaining their primary function in smoothing, shaping, or cleaning surfaces. The definition is written on the board.
Pupils’ Activity: Pupils listen attentively, ask questions for clarification, and copy the definition into their notebooks.
Learning Point: Pupils understand the fundamental concept of abrasives.

Step 3: Types of Abrasives

Time: 10 minutes
Teaching Skill: Classification/Illustration
Teacher’s Activity: The teacher explains and illustrates the different types of abrasives, categorizing them into natural (e.g., garnet, emery) and synthetic (e.g., aluminium oxide, silicon carbide). Samples of each type are shown and discussed.
Pupils’ Activity: Pupils observe the samples, identify the different types, and take notes on the classification.
Learning Point: Pupils can identify and differentiate between various types of abrasive materials.

Step 4: Selection of Abrasives

Time: 8 minutes
Teaching Skill: Explanation/Discussion
Teacher’s Activity: The teacher leads a discussion on the important factors to consider when selecting an abrasive for a particular job. Factors such as the type of material, desired finish, and cost are highlighted.
Pupils’ Activity: Pupils contribute to the discussion, ask relevant questions, and note down the selection criteria.
Learning Point: Pupils understand the principles for choosing the correct abrasive for different tasks.

Step 5: Uses of Different Abrasive Grades

Time: 7 minutes
Teaching Skill: Explanation/Application
Teacher’s Activity: The teacher explains the concept of abrasive grit sizes and demonstrates how different grades (coarse, medium, fine, very fine) are used for various applications, showing examples on different material samples if available.
Pupils’ Activity: Pupils observe the demonstration, relate grit size to specific uses, and record the information.
Learning Point: Pupils know which abrasive grade is appropriate for specific finishing stages or tasks.

Step 6: Practical Demonstration

Time: 5 minutes
Teaching Skill: Demonstration/Practical Application
Teacher’s Activity: The teacher briefly demonstrates the proper technique for using different abrasive grades on a piece of wood, showing the effect of each grade on the surface finish. Safety precautions are also emphasized.
Pupils’ Activity: Pupils observe the demonstration carefully, noting the techniques and safety measures.
Learning Point: Pupils observe the practical application of abrasives and understand proper usage.

Step 7: Evaluation/Review

Time: 5 minutes
Teaching Skill: Questioning/Assessment
Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

Define an abrasive.
Mention two natural and two synthetic types of abrasives.
State three factors to consider when selecting an abrasive.
Explain the difference between coarse and fine grit abrasives in terms of use.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 5 minutes
Teaching Skill: Summarization/Assignment
Teacher’s Activity: The teacher summarizes the key learning points of the lesson, emphasizing the importance of correct abrasive selection and use in carpentry. Homework is assigned.
Pupils’ Activity: Pupils listen to the summary, ask any final questions, and note down the homework.
Learning Point: Pupils consolidate their understanding and prepare for further learning.

Lesson Keywords

Abrasives – Hard materials used for grinding, polishing, or cleaning surfaces.
Grit – A measure of the coarseness of abrasive particles.
Emery – A natural abrasive, a dark granular mineral.
Sandpaper – A common abrasive material consisting of paper or cloth with abrasive particles glued to one side.
Aluminium Oxide – A common synthetic abrasive, known for its toughness.
Silicon Carbide – A synthetic abrasive, harder and sharper than aluminium oxide.
Garnet – A natural abrasive, often used for sanding wood.

Differentiation

For pupils who grasp concepts quickly, they can research specific applications of very fine abrasives or different types of sanding machines. For pupils needing more support, the teacher will provide simplified explanations and more direct guidance during the identification and selection exercises.

Note for teachers using this lesson plan

Teachers should ensure a variety of abrasive samples are available for pupils to touch and examine. Emphasize safety precautions when handling and using abrasives, especially if any practical demonstrations involve tools. Encourage pupils to relate the lesson to real-life applications in their homes or communities.