Class: Senior Secondary School 2 (SS2 / SSS 2)
Term: Second Term
Week: 4
Age: 16 years
Duration: 45 minutes
Subject: Metal Work
Curriculum Theme: Pre-Vocational Studies
Previous Lesson: Shielded Metal Arc Welding (SMAW).
Topic: Striking the Arc
Subject Matter: Meaning of striking the arc (initiating welding arc), tapping method, scratching method

Specific Objectives

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

Cognitive Domain:

Define what is meant by striking the arc in welding.
Explain the tapping method of striking an arc.
Describe the scratching method of striking an arc.

Affective Domain:

Appreciate the importance of proper arc striking techniques for effective welding.
Develop patience and precision when practicing arc striking.

Psychomotor Domain:

Demonstrate the tapping method to strike an arc.
Demonstrate the scratching method to strike an arc.

Observe safety precautions while practicing arc striking.
Collaborate with peers during practical sessions.

Reference Materials

The following resources were used in planning this lesson:

Senior Secondary Schools Education Curriculum
State Unified Scheme of Work
Metal Work for Senior Secondary Schools Textbook

Instructional Materials

The teacher will teach this lesson with the aid of:

Electrodes
Welding machine
Steel plates
Welding helmet
Welding gloves
Apron

Rationale for the Lesson

Understanding how to strike an arc correctly is the fundamental first step in arc welding. This skill is essential for pupils to initiate the welding process safely and effectively, laying the groundwork for producing quality welds in future practical work.

Prerequisite/Previous Knowledge

Pupils should have basic knowledge of arc welding equipment and general workshop safety rules.

Lesson Content/Board Summary

Striking the Arc

Meaning of Striking the Arc

Striking the arc is the process of initiating an electrical arc between the electrode and the workpiece to start the welding process. It is the first step in arc welding and requires practice to master.

Methods of Striking the Arc

There are two main methods used to strike an arc in arc welding:

Tapping Method
Scratching Method

1. Tapping Method

In the tapping method, the electrode is brought into contact with the workpiece with a quick tapping motion, then immediately lifted slightly to create the arc gap.

Steps for Tapping Method:

Hold the electrode perpendicular to the workpiece.
Tap the electrode quickly onto the workpiece.
As soon as contact is made, lift the electrode slightly (about 2-3 mm) to establish the arc.
Maintain the arc gap to continue welding.

2. Scratching Method

The scratching method involves dragging the electrode across the workpiece like striking a match, then lifting it slightly to form the arc.

Steps for Scratching Method:

Hold the electrode at a slight angle to the workpiece.
Drag the tip of the electrode across the workpiece surface, similar to striking a match.
As soon as the arc ignites, lift the electrode slightly (about 2-3 mm) and maintain the arc gap.
Continue with the welding process.

Safety Precautions During Arc Striking

Always wear appropriate personal protective equipment (PPE) such as a welding helmet, gloves, and protective clothing.
Ensure the work area is free from flammable materials.
Confirm the welding machine is properly grounded.
Avoid looking at the arc directly without a welding helmet to prevent arc eye.

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 introduces the new topic, “Striking the Arc,” by asking pupils if they know how welding starts.
Pupils’ Activity: Pupils respond to the teacher’s questions and listen attentively to the introduction.
Learning Point: Pupils are prepared for the new lesson and connect it to prior knowledge.

Step 2: Explanation of Striking the Arc

Time: 8 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher explains the meaning of “striking the arc” as initiating the electrical arc between the electrode and the workpiece, emphasizing its importance as the first step in welding.
Pupils’ Activity: Pupils listen, take notes, and ask questions for clarification.
Learning Point: Pupils understand the fundamental concept of striking the arc.

Step 3: Explanation and Demonstration of Tapping Method

Time: 8 minutes
Teaching Skill: Demonstration/Explanation
Teacher’s Activity: The teacher explains the tapping method, outlining the steps involved. The teacher then demonstrates the tapping method using the welding machine, electrode, and steel plate, ensuring safety.
Pupils’ Activity: Pupils observe the demonstration carefully, noting the technique and safety measures. They may ask questions.
Learning Point: Pupils learn the correct procedure for the tapping method.

Step 4: Explanation and Demonstration of Scratching Method

Time: 8 minutes
Teaching Skill: Demonstration/Explanation
Teacher’s Activity: The teacher explains the scratching method, detailing its steps. The teacher then demonstrates the scratching method, comparing it to striking a match, while adhering to safety protocols.
Pupils’ Activity: Pupils pay close attention to the demonstration and explanations, comparing it to the tapping method.
Learning Point: Pupils learn the correct procedure for the scratching method.

Step 5: Discussion on Safety Precautions

Time: 4 minutes
Teaching Skill: Discussion/Reinforcement
Teacher’s Activity: The teacher leads a discussion on the necessary safety precautions to observe while striking an arc and performing any welding operation.
Pupils’ Activity: Pupils contribute to the discussion by mentioning various safety measures and asking relevant questions.
Learning Point: Pupils understand the critical importance of safety during welding.

Step 6: Practical Practice/Supervision

Time: 7 minutes
Teaching Skill: Practical Application/Supervision
Teacher’s Activity: The teacher guides pupils to individually practice striking the arc using both the tapping and scratching methods under strict supervision, correcting errors as needed.
Pupils’ Activity: Pupils take turns to practice striking the arc, applying the techniques learned, and seeking guidance from the teacher.
Learning Point: Pupils gain hands-on experience and improve their arc striking skills.

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 meant by “striking the arc”?
Mention two methods of striking an arc.
Briefly explain the tapping method of striking an arc.
Describe the scratching method of striking an arc.

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 mastering arc striking. The teacher then assigns relevant homework.
Pupils’ Activity: Pupils listen to the summary and copy down the assigned homework.
Learning Point: Pupils consolidate their learning and prepare for further practice.

Lesson Keywords

Striking the Arc – The process of initiating an electrical arc between an electrode and a workpiece to start welding.
Tapping Method – A technique to strike an arc by quickly tapping the electrode on the workpiece and lifting it slightly.
Scratching Method – A technique to strike an arc by dragging the electrode across the workpiece like a match and then lifting it slightly.
Arc Welding – A welding process that uses an electric arc to create heat to melt and join metals.
Electrode – A metal rod or wire that conducts electric current and melts to form part of the weld.

Differentiation

For pupils who grasp the concept quickly, the teacher can provide additional challenges such as maintaining a consistent arc length. For those needing more support, the teacher can offer one-on-one guidance and allow more practice time with direct supervision, using visual cues and repeated demonstrations.

Note for teachers using this lesson plan

Ensure all safety equipment is available and in good condition before any practical demonstration or pupil practice. Emphasize safety throughout the lesson. Encourage pupils to practice diligently, as arc striking requires significant hand-eye coordination and practice to master.