Class: Senior Secondary School 1 (SS1, SS 1, SSS1, SSS 1)
Term: 3rd Term
Week: 10
Age: 15 years
Duration: 45 minutes
Subject: Metal Work
Curriculum Theme: Pre-Vocational Studies
Previous Lesson: Reamers: Classification and Practical Reaming.
Topic: Grinding Machine and Grinding Wheels
Subject Matter: Definition of grinding machine, functions of grinding machine, grinding wheels and their use, setting up grinding wheel, grinding a workpiece safely.

Specific Objectives

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

Cognitive Domain:

Define a grinding machine.
State at least three functions of a grinding machine.
Identify different types of grinding wheels and their uses.
List the steps for safely setting up a grinding wheel.
Explain safety precautions when operating a grinding machine.

Affective Domain:

Appreciate the importance of safety when using power tools.
Demonstrate carefulness and attention to detail during practical tasks.

Psychomotor Domain:

Properly set up a grinding wheel on a bench grinder.
Safely grind a workpiece to a desired shape or finish under supervision.

Observe workshop safety rules individually and collectively.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Metal Work.
State Unified Scheme of Work for Senior Secondary Metal Work.
Akinwumi, O. (2018). *Basic Metal Work for Senior Secondary Schools*. Evans Publishers.
https://example.com/metalwork_grinding_safety
https://example.com/grinding_wheel_types

Instructional Materials

The teacher will teach this lesson with the aid of:

A functional bench grinder.
Various types of grinding wheels.
Safety goggles.
Sample workpieces (e.g., metal bars, old tools for sharpening).
Dust mask and protective gloves.
Whiteboard and markers.

Rationale for the Lesson

This lesson helps pupils understand how to use a grinding machine, which is a common tool in metalwork. Knowing how to operate it safely and effectively is important for shaping and finishing metal projects, and for ensuring their personal safety in the workshop.

Prerequisite/Previous Knowledge

Pupils have basic knowledge of hand tools used in metalwork and understand general workshop safety rules.

Lesson Content/Board Summary

Grinding Machine and Grinding Wheels

Definition of Grinding Machine

A grinding machine is a power-driven machine tool that uses an abrasive wheel as the cutting tool. It is used for grinding, which is an abrasive machining process that removes material from a workpiece by rubbing a grinding wheel against it.

Functions of a Grinding Machine

The following are common functions of a grinding machine:

Sharpening cutting tools like chisels, drill bits, and lathe tools.
Removing excess material from workpieces (e.g., burrs, rough edges).
Finishing surfaces to achieve desired smoothness or accuracy.
Shaping workpieces to specific profiles.
Cleaning rusty or corroded metal surfaces.

Grinding Wheels and Their Uses

Grinding wheels are abrasive tools made from various materials, bonded together, and shaped into a wheel. Their properties depend on the abrasive type, grit size, bond type, and grade.

Common types of grinding wheels include:

Aluminium Oxide Wheels: Used for grinding high-tensile strength materials like steel and ferrous alloys.
Silicon Carbide Wheels: Used for grinding low-tensile strength materials such as cast iron, non-ferrous metals (aluminium, brass), and non-metallic materials.

Setting Up a Grinding Wheel

Proper setup of a grinding wheel is important for safety and effective operation. The steps generally include:

Ensure the machine is unplugged or switched off.
Select the correct grinding wheel for the task and material.
Inspect the wheel for cracks or damage; perform a “ring test.”
Mount the wheel onto the spindle with flanges and tighten the nut securely, but not excessively.
Adjust the tool rest to be within 1/16 inch (approx. 1.5 mm) of the grinding wheel.
Ensure the spark arrestor is correctly positioned.
Wear appropriate Personal Protective Equipment (PPE) before switching on.

Safe Grinding Practices

Adhering to safety practices is essential when using a grinding machine. The following are important safety measures:

Always wear safety goggles or a face shield to protect eyes from sparks and flying particles.
Ensure the grinding wheel is well-guarded and the tool rest is properly adjusted.
Never grind on the side of the wheel unless it is designed for it.
Use light pressure and keep the workpiece moving to prevent overheating.
Avoid wearing loose clothing, jewellery, or long hair that can get caught in the machine.
Do not wear gloves while operating the machine as they can get caught.
Ensure adequate ventilation to remove grinding dust.
Never force a workpiece against a cold wheel, as this can cause the wheel to shatter.
Keep hands clear of the rotating wheel.
Switch off and unplug the machine after use and before making adjustments.

Teaching Methods/Instructional Techniques

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

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction/Questioning
Teacher’s Activity: The teacher greets the pupils and asks them about tools they use to sharpen other tools or remove rough edges from metal. The teacher introduces the grinding machine as one such important tool used in metalwork.
Pupils’ Activity: Pupils respond to questions and listen attentively.
Learning Point: Pupils are introduced to the topic and its relevance.

Step 2: Definition and Functions of a Grinding Machine

Time: 10 minutes
Teaching Skill: Explanation/Lecture
Teacher’s Activity: The teacher defines a grinding machine, explaining its basic principle of operation. The teacher then discusses and lists the various functions of a grinding machine, writing key points on the board.
Pupils’ Activity: Pupils listen, take notes, and ask questions for clarification.
Learning Point: Pupils understand what a grinding machine is and its primary uses.

Step 3: Grinding Wheels and Their Uses

Time: 7 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher displays different types of grinding wheels and explains their characteristics (e.g., abrasive material, grit size). The teacher explains which materials each type of wheel is suitable for grinding.
Pupils’ Activity: Pupils observe the grinding wheels, listen to explanations, and note their uses.
Learning Point: Pupils identify different grinding wheels and know their appropriate applications.

Step 4: Setting Up a Grinding Wheel and Safe Grinding Practices

Time: 10 minutes
Teaching Skill: Demonstration/Explanation
Teacher’s Activity: The teacher demonstrates the correct and safe procedure for setting up a grinding wheel on the bench grinder, emphasizing safety checks. The teacher then explains and lists important safety practices to follow when operating the machine, stressing the importance of PPE.
Pupils’ Activity: Pupils observe the demonstration carefully, ask questions, and take notes on the setup process and safety rules.
Learning Point: Pupils learn the practical steps for setting up a grinding wheel and critical safety precautions.

Step 5: Practical Demonstration of Grinding a Workpiece

Time: 5 minutes
Teaching Skill: Demonstration
Teacher’s Activity: Wearing appropriate PPE, the teacher demonstrates how to safely grind a small workpiece, showing correct posture, pressure, and movement. The teacher highlights common mistakes to avoid.
Pupils’ Activity: Pupils closely observe the teacher’s demonstration of grinding techniques.
Learning Point: Pupils see the practical application of the lesson and safe handling of the machine.

Step 6: Supervised Practical Activity

Time: 15 minutes
Teaching Skill: Practical Supervision/Guidance
Teacher’s Activity: Under strict supervision and ensuring all pupils wear safety goggles, the teacher allows pupils (in small groups or individually, depending on equipment) to practice basic grinding on a given workpiece. The teacher provides immediate feedback and corrects errors.
Pupils’ Activity: Pupils carefully perform basic grinding tasks under supervision, applying the safety rules and techniques learned.
Learning Point: Pupils gain hands-on experience in using the grinding machine safely.

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

What is a grinding machine?
Mention three functions of a grinding machine.
List two common types of grinding wheels and state what materials they are used for.
State three safety precautions to observe when using a grinding machine.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 3 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the main points of the lesson, reiterating the importance of safety and proper use of the grinding machine. The teacher assigns homework for pupils to research other types of grinding machines.
Pupils’ Activity: Pupils listen to the summary and copy the homework.
Learning Point: Pupils consolidate their learning and are given a task for further exploration.

Lesson Keywords

Grinding Machine – A power tool that uses an abrasive wheel to remove material from a workpiece.
Grinding Wheel – An abrasive tool made from bonded abrasive particles, used for grinding.
Abrasive – A material, typically a mineral, used for grinding, polishing, or cutting other materials.
Tool Rest – An adjustable support near the grinding wheel for resting the workpiece.
PPE (Personal Protective Equipment) – Equipment such as safety goggles, gloves, and face shields worn to minimize exposure to hazards.

Differentiation

For pupils who grasp concepts quickly, the teacher can challenge them to identify specific parts of the grinding machine or research different grinding operations. For pupils needing more support, the teacher will provide closer supervision during practical activities and simplify explanations, perhaps using visual aids more extensively.

Note for teachers using this lesson plan

Prior to the lesson, ensure the bench grinder is in good working condition and securely fastened. All safety equipment must be available and checked. Emphasize safety throughout the lesson, especially during the practical session. Supervision must be constant and vigilant during practical work to prevent accidents.