Class: Senior Secondary School 1 (SS1, SS 1, SSS1, SSS 1)
Term: 3rd Term
Week: 5
Age: 15 years
Duration: 45 minutes
Subject: Metal Work
Curriculum Theme: Pre-Vocational Studies
Previous Lesson: Drills: Parts and Drill Size Selection.
Topic: Drill breakage and their causes
Subject Matter: causes of drill breakage, correct fixing of drills in the drill chuck, use of coolant, safe drilling practice, using a reamer to enlarge an already drilled hole

Specific Objectives

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

Cognitive Domain:

Define drill breakage.
List at least three causes of drill breakage.
State the correct procedure for fixing a drill in the drill chuck.
Explain the importance of using coolant during drilling.
Identify safe drilling practices.
Describe how a reamer is used to enlarge a drilled hole.

Affective Domain:

Appreciate the importance of safety when operating drilling machines.
Value the use of correct procedures for tool handling and operation.
Show care for drilling equipment and materials.

Psychomotor Domain:

Demonstrate the correct method of fixing a drill bit in the drill chuck.
Apply coolant correctly during a drilling operation.
Perform basic safe drilling practices under supervision.
Illustrate the use of a reamer to enlarge a pre-drilled hole.

Work cooperatively with peers to observe safety rules in the workshop.
Participate actively in discussions about safe workshop practices.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Metal Work (Senior Secondary Education)
State Unified Scheme of Work for Senior Secondary School Metal Work
Metal Work for Senior Secondary Schools by A.O. Adewale and S.A. Olaitan

Instructional Materials

The teacher will teach this lesson with the aid of:

Drill press
Drill chuck
Coolant
Reamer
Sample metal piece
Safety goggles
Work gloves

Rationale for the Lesson

This lesson helps pupils understand the reasons why drill bits break, which is essential for preventing accidents and damage to tools. Learning correct procedures and safe practices ensures pupils can operate drilling machines effectively and safely in the workshop, preparing them for practical tasks.

Prerequisite/Previous Knowledge

Pupils have basic knowledge of the drilling machine, its main parts, and simple drilling operations.

Lesson Content/Board Summary

Drill Breakage and Safe Drilling Practices

Causes of Drill Breakage

Drill bits can break due to various reasons, often related to improper use or setup.

The common causes of drill breakage include:

Excessive feed pressure.
Incorrect cutting speed.
Poorly sharpened drill bit.
Improperly secured workpiece.
Drill bit not properly fixed in the chuck.
Lack of coolant or improper use of coolant.
Drill bit hitting an obstruction.
Vibration of the workpiece or machine.

Correct Fixing of Drills in the Drill Chuck

Properly fixing a drill bit in the chuck is essential for safety and efficient drilling.

Steps for correct fixing:

Ensure the drill chuck jaws are clean and free from debris.
Insert the shank of the drill bit into the chuck jaws, making sure it is seated firmly and centrally.
Tighten the chuck jaws securely using the chuck key. Ensure all three holes are tightened to apply even pressure.
Remove the chuck key immediately after tightening to prevent it from being thrown during operation.

Use of Coolant During Drilling

Coolant is a fluid used to reduce heat and friction during machining operations.

The importance of using coolant includes:

Cooling the drill bit and workpiece, preventing overheating.
Lubricating the cutting edge, reducing friction and wear.
Washing away chips from the cutting area, improving visibility and preventing clogging.
Extending the life of the drill bit.
Improving the surface finish of the drilled hole.

Safe Drilling Practice

Operating a drilling machine requires adherence to strict safety rules to prevent injuries.

Essential safe drilling practices are:

Always wear appropriate Personal Protective Equipment (PPE) such as safety goggles and work gloves.
Secure the workpiece firmly in a vice or clamp to prevent it from spinning.
Select the correct drill bit size and type for the material being drilled.
Ensure the drill bit is properly sharpened and free from defects.
Set the correct cutting speed for the material.
Start the machine and allow it to reach full speed before feeding the drill.
Apply steady, even feed pressure; avoid excessive force.
Use coolant as appropriate for the material and operation.
Clear chips regularly using a brush, never with bare hands.
Never try to stop the chuck or workpiece with your hand.
Turn off the machine and allow it to stop completely before making adjustments or measurements.

Using a Reamer to Enlarge a Drilled Hole

A reamer is a multi-fluted cutting tool used to enlarge and finish a pre-drilled hole to a precise size and achieve a smooth surface finish.

Procedure for using a reamer:

Drill a hole slightly smaller than the desired final reamed size.
Secure the workpiece firmly.
Mount the reamer in the drill chuck.
Set a slow speed for the drilling machine.
Apply cutting fluid generously.
Feed the reamer into the pre-drilled hole slowly and steadily.
Avoid stopping the reamer once it has started cutting.
Withdraw the reamer carefully once the desired depth is reached.

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 and asks them to recall previous lessons on drilling machines. The teacher then asks questions like, “What happens if a drill bit is not properly secured in the chuck?” and “Why do drill bits sometimes break during use?” This leads to the topic of drill breakage and safe drilling practices.
Pupils’ Activity: Pupils respond to the teacher’s questions, sharing their prior knowledge and experiences.
Learning Point: Pupils are introduced to the topic and its relevance to practical metalwork.

Step 2: Causes of Drill Breakage

Time: 8 minutes
Teaching Skill: Explanation/Lecture
Teacher’s Activity: The teacher explains what drill breakage is and then lists and explains the common causes of drill breakage, referring to the board summary. The teacher encourages pupils to share observations from their practical experiences.
Pupils’ Activity: Pupils listen attentively, take notes, and contribute to the discussion by sharing their observations.
Learning Point: Pupils understand the factors that lead to drill breakage.

Step 3: Correct Fixing of Drills and Use of Coolant

Time: 8 minutes
Teaching Skill: Demonstration/Explanation
Teacher’s Activity: The teacher demonstrates the correct method of fixing a drill bit in the drill chuck using a drill press and chuck key. The teacher also explains the importance of coolant and demonstrates its application during a simulated drilling operation on a sample metal piece.
Pupils’ Activity: Pupils observe the demonstration carefully, ask questions for clarification, and take notes.
Learning Point: Pupils learn the correct procedure for securing drill bits and the proper use of coolant.

Step 4: Safe Drilling Practice

Time: 8 minutes
Teaching Skill: Discussion/Instruction
Teacher’s Activity: The teacher discusses and explains various safe drilling practices, emphasizing the importance of PPE, securing the workpiece, and selecting correct speeds and feeds. The teacher supervises pupils as they briefly practice securing a workpiece and wearing safety gear.
Pupils’ Activity: Pupils listen, ask questions, and practice the initial steps of safe drilling under supervision.
Learning Point: Pupils understand and begin to practice essential safety measures for drilling.

Step 5: Using a Reamer to Enlarge a Drilled Hole

Time: 8 minutes
Teaching Skill: Demonstration/Explanation
Teacher’s Activity: The teacher defines a reamer and explains its purpose. The teacher then demonstrates how to use a reamer to enlarge a pre-drilled hole on a sample metal piece, highlighting the slow speed and steady feed required.
Pupils’ Activity: Pupils observe the demonstration, ask questions about the reaming process, and note down the steps.
Learning Point: Pupils understand the function and application of a reamer.

Step 6: Practical Application/Reinforcement

Time: 5 minutes
Teaching Skill: Practical Supervision
Teacher’s Activity: The teacher provides a brief opportunity for pupils to practice securing a drill bit in the chuck and correctly securing a workpiece under close supervision, reinforcing the learned procedures.
Pupils’ Activity: Pupils practice the demonstrated skills with close teacher supervision and assistance.
Learning Point: Pupils gain hands-on experience in tool setup and workpiece securing.

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 drill breakage.
List three common causes of drill breakage.
State two steps for correctly fixing a drill in the drill chuck.
Explain the importance of using coolant during drilling.
Mention two safe drilling practices.
What is a reamer primarily used for?

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 2 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the key points of the lesson, reiterating the importance of safety and correct procedures in metalwork. The teacher assigns homework for pupils to research different types of coolants used in drilling.
Pupils’ Activity: Pupils listen to the summary and copy the homework assignment.
Learning Point: Pupils consolidate their learning and are given a task for further study.

Lesson Keywords

Drill breakage – The fracturing or breaking of a drill bit during a drilling operation.
Drill chuck – A device used to hold a drill bit securely in a drilling machine.
Coolant – A fluid used to cool and lubricate cutting tools and workpieces during machining.
Reamer – A multi-fluted cutting tool used to enlarge and finish a drilled hole to a precise size and smooth surface.
Safe drilling practice – Procedures and precautions followed to prevent accidents and injuries while operating a drilling machine.

Differentiation

For pupils who grasp concepts quickly, they can assist peers in practical demonstrations or research additional types of drill bits and their applications. For pupils needing more support, the teacher will provide individualized attention during practical sessions and simplify explanations with additional visual aids.

Note for teachers using this lesson plan

Ensure all safety precautions are strictly followed during demonstrations and supervised practical sessions. Emphasize the “never” rules in the workshop. Have all instructional materials ready and in good working condition before the lesson. Encourage active participation and questions from pupils to ensure deep understanding of safety-critical aspects.