Class: Senior Secondary School 2 (SS2 / SSS2)
Term: 1st Term
Week: 4
Age: 16 years
Duration: 45 minutes
Subject: Metal Work
Curriculum Theme: Pre-Vocational Studies
Previous Lesson: Brazing and Methods of Brazing.
Topic: Torch Brazing
Subject Matter: Meaning of torch brazing (brazing using flame), materials for brazing, tools and equipment for brazing

Specific Objectives

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

Cognitive Domain:

Define torch brazing.
Identify the materials used in torch brazing.
List the tools and equipment required for torch brazing.

Affective Domain:

Appreciate the importance of safety precautions during brazing operations.
Develop an interest in practical metal joining techniques.

Psychomotor Domain:

Observe a demonstration of torch brazing operation.
Identify the main components of an oxy-acetylene set.

Collaborate with peers during observation and discussion.

Reference Materials

The following resources were used in planning this lesson:

Senior Secondary Schools Education Curriculum
State Unified Scheme of Work
Metalwork for Senior Secondary Schools by A.A. Adekunle

Instructional Materials

The teacher will teach this lesson with the aid of:

Oxy-acetylene set
Filler rod
Metal sheets
Safety goggles
Gloves
Fire extinguisher
Wire brush

Rationale for the Lesson

This lesson helps pupils understand a common method of joining metals called torch brazing. It enables them to identify the necessary materials and tools, and to appreciate the safety measures involved in practical metalwork, which is useful for technical skills development.

Prerequisite/Previous Knowledge

Pupils have basic knowledge of different metal joining methods and general workshop safety rules.

Lesson Content/Board Summary

Torch Brazing

Meaning of Torch Brazing

Torch brazing is a metal-joining process in which a filler metal is heated to its melting point (above 450°C) and distributed between two or more close-fitting parts by capillary action. The filler metal flows into the joint and, upon cooling, solidifies to form a strong bond between the base metals without melting the base metals themselves. It commonly uses an oxy-acetylene flame or other gas flames to provide the heat.

Materials for Brazing

The following are materials used for brazing:

Base Metals – These are the metals to be joined (e.g., steel, copper, brass).
Filler Metal (Brazing Alloy) – This is a metal with a lower melting point than the base metals, which melts and flows into the joint. Common examples include silver alloys, copper-phosphorus alloys, and brass alloys.
Flux – This is a chemical compound applied to the joint surfaces to prevent oxidation and clean the metal during heating, allowing the filler metal to flow freely.

Tools and Equipment for Brazing

The following are tools and equipment required for brazing:

Oxy-acetylene Set – This consists of oxygen and acetylene cylinders, regulators, hoses, and a torch for mixing and igniting the gases to produce a high-temperature flame.
Brazing Torch – Used to direct the flame to the workpieces.
Goggles/Face Shield – For eye and face protection from intense light and heat.
Gloves – Heat-resistant gloves for hand protection.
Fire Extinguisher – For safety in case of fire.
Wire Brush – Used for cleaning the joint area before and after brazing.
Tongs/Clamps – Used for holding workpieces securely during the process.

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 asks pupils to mention different ways metals can be joined together.
Pupils’ Activity: Pupils respond by mentioning methods like welding, soldering, and riveting.
Learning Point: Pupils recall previous knowledge on metal joining techniques.

Step 2: Meaning of Torch Brazing

Time: 10 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher explains the meaning of torch brazing, emphasizing that the base metals do not melt during the process.
Pupils’ Activity: Pupils listen attentively and take notes on the definition.
Learning Point: Pupils understand the definition and basic principle of torch brazing.

Step 3: Materials for Brazing

Time: 7 minutes
Teaching Skill: Listing/Identification
Teacher’s Activity: The teacher discusses and lists the materials used for brazing, such as base metals, filler metal, and flux.
Pupils’ Activity: Pupils identify and write down the various materials discussed.
Learning Point: Pupils identify the essential materials required for brazing.

Step 4: Tools and Equipment for Brazing

Time: 7 minutes
Teaching Skill: Description/Visual Aid
Teacher’s Activity: The teacher presents and explains the tools and equipment, including the oxy-acetylene set, torch, and safety gear, using visual aids.
Pupils’ Activity: Pupils observe the tools and equipment and list them in their notebooks.
Learning Point: Pupils identify and understand the function of common brazing tools and equipment.

Step 5: Demonstration of Torch Brazing

Time: 8 minutes
Teaching Skill: Demonstration/Practical Application
Teacher’s Activity: The teacher demonstrates a simple brazing operation using sheet metals and an oxy-acetylene flame to join metal pieces, highlighting safety rules throughout.
Pupils’ Activity: Pupils carefully observe the brazing steps and the safety rules being applied.
Learning Point: Pupils observe the practical application of brazing and learn about safety procedures.

Step 6: Safety Precautions

Time: 3 minutes
Teaching Skill: Emphasis/Reinforcement
Teacher’s Activity: The teacher emphasizes the critical safety precautions that must be taken during brazing operations to prevent accidents.
Pupils’ Activity: Pupils listen carefully and note down the important safety measures.
Learning Point: Pupils understand the importance of safety when performing brazing work.

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 torch brazing?
Mention two materials used in torch brazing.
List three tools or equipment needed for torch brazing.
Why is flux important in brazing?

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/Assignment
Teacher’s Activity: The teacher summarizes the key points of the lesson and assigns homework: “Draw and label an oxy-acetylene torch.”
Pupils’ Activity: Pupils listen, copy the homework, and prepare for the next lesson.
Learning Point: Consolidates learning and provides an opportunity for practice and reinforcement.

Lesson Keywords

Torch Brazing – A metal joining process using a filler metal melted by a torch without melting the base metals.
Filler Rod – The consumable metal alloy used to fill the joint during brazing.
Flux – A chemical cleaning agent applied to metal surfaces before brazing to prevent oxidation.
Oxy-acetylene – A type of gas mixture used in torches to produce a high-temperature flame for brazing and welding.
Brazing Alloy – Another term for filler metal used in brazing.

Differentiation

For visual learners, the teacher will use diagrams of equipment and a live demonstration. Kinesthetic learners will benefit from observing the practical demonstration closely. Struggling pupils will receive additional guidance and simpler explanations, while advanced pupils can research different types of brazing alloys and their applications.

Note for teachers using this lesson plan

Ensure all safety precautions are strictly followed during the demonstration. Emphasize the difference between brazing and welding, particularly that the base metals do not melt in brazing. Encourage pupils to ask questions during the demonstration to clarify any doubts.