Class: Senior Secondary School 1 (SS1 / SSS 1)
Term: Second Term
Week: 6
Age: 15 years
Duration: 45 minutes
Subject: Furniture Making
Curriculum Theme: Trade
Previous Lesson: Methods Of Timber Conversion: Types And Processes.
Topic: Advantages and Disadvantages of Timber Conversion
Subject Matter: Advantages of timber conversion, Disadvantages of timber conversion, Method comparison

Specific Objectives

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

Cognitive Domain:

Define timber conversion.
State at least three advantages of timber conversion.
State at least three disadvantages of timber conversion.
Compare different methods of timber conversion.

Affective Domain:

Appreciate the importance of proper timber conversion for furniture making.
Discuss the factors influencing the choice of conversion method.

Psychomotor Domain:

Illustrate the differences between various timber conversion methods using a chart.
Identify correctly converted timber samples.

Participate actively in group discussions about timber conversion.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Technology.
State Unified Scheme of Work for Senior Secondary Schools.
Practical Woodwork for Senior Secondary Schools, Book 1.

Instructional Materials

The teacher will teach this lesson with the aid of:

A comparison chart showing different timber conversion methods.
Samples of timber converted using various methods (e.g., plain sawn, quarter sawn).
Whiteboard and markers.

Rationale for the Lesson

Understanding the advantages and disadvantages of timber conversion helps pupils appreciate why timber is processed before use. This knowledge enables them to make informed decisions about the type of timber to select for different furniture projects, leading to better quality and durable products.

Prerequisite/Previous Knowledge

Pupils are expected to have prior knowledge of what timber is, its sources, and some basic methods of felling trees.

Lesson Content/Board Summary

Advantages and Disadvantages of Timber Conversion

What is Timber Conversion?

Timber conversion is the process of sawing felled logs into usable sizes and shapes, such as planks, boards, and beams, for various purposes, especially in construction and furniture making.

Advantages of Timber Conversion

The following are the advantages of timber conversion:

It reduces the weight of the timber, making it easier to transport.
It allows for quicker and more efficient seasoning (drying) of the wood.
It helps to remove defects like knots, splits, and decayed parts.
It makes the timber easier to handle and work with for specific projects.
It enables the production of different sizes and shapes of wood for various uses.
It reduces the risk of insect attacks and fungal decay in the stored timber.

Disadvantages of Timber Conversion

The following are the disadvantages of timber conversion:

It leads to a significant amount of wood waste (sawdust and off-cuts).
It requires specialized machinery and skilled labour, which can be costly.
Incorrect conversion methods can lead to warping, twisting, and splitting of the timber during drying.
It exposes the inner parts of the wood to the atmosphere, which can sometimes accelerate decay if not properly handled.
It can reduce the overall strength of the timber if not done correctly.

Comparison of Timber Conversion Methods

There are different methods of converting timber, each with its own characteristics and suitability for different purposes. Common methods include plain sawing (through and through), quarter sawing, and tangential sawing. Comparing these methods helps in selecting the most appropriate one for a given application based on factors like grain pattern, stability, and waste generation.

The following are common timber conversion methods:

Plain Sawing (Through and Through): This is the simplest and most economical method. It produces boards with varied grain patterns and is prone to warping. It yields the most timber from a log.
Quarter Sawing: This method produces boards with a uniform grain pattern (medullary rays exposed) and greater stability, making it less prone to warping and twisting. It is more wasteful and therefore more expensive.
Tangential Sawing: This method involves cutting parallel to the growth rings, producing boards with distinctive flame-like grain patterns. It is often used for decorative purposes but can be prone to cupping.

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 on timber sources, and then introduces the new topic by asking pupils why felled trees are not used directly as furniture without being cut into smaller pieces.
Pupils’ Activity: Pupils respond to the teacher’s questions and listen attentively.
Learning Point: Pupils recall previous knowledge and are introduced to the new lesson.

Step 2: Explanation of Advantages

Time: 8 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher defines timber conversion and explains the advantages of converting timber, using the comparison chart and timber samples to illustrate points. The teacher writes key points on the board.
Pupils’ Activity: Pupils listen, observe the instructional materials, ask questions, and take notes.
Learning Point: Pupils understand the benefits of timber conversion.

Step 3: Explanation of Disadvantages

Time: 8 minutes
Teaching Skill: Explanation
Teacher’s Activity: The teacher explains the disadvantages of timber conversion, highlighting the challenges and potential waste involved. The teacher continues to write key points on the board.
Pupils’ Activity: Pupils listen, contribute to the discussion, and take notes.
Learning Point: Pupils understand the drawbacks and challenges associated with timber conversion.

Step 4: Introduction to Conversion Methods

Time: 8 minutes
Teaching Skill: Demonstration/Illustration
Teacher’s Activity: The teacher introduces different timber conversion methods (e.g., plain sawing, quarter sawing, tangential sawing) using the comparison chart and physical timber samples. The teacher explains the basic principle of each method.
Pupils’ Activity: Pupils observe the chart and samples, ask questions, and identify differences.
Learning Point: Pupils are exposed to various ways timber is converted.

Step 5: Method Comparison

Time: 5 minutes
Teaching Skill: Discussion/Analysis
Teacher’s Activity: The teacher facilitates a brief discussion comparing the advantages and disadvantages of each conversion method, guiding pupils to understand why different methods are chosen for different purposes.
Pupils’ Activity: Pupils participate in the discussion, comparing the methods and stating their observations.
Learning Point: Pupils can identify the differences and suitability of various timber conversion methods.

Step 6: Class Activity

Time: 4 minutes
Teaching Skill: Application
Teacher’s Activity: The teacher asks pupils to, in pairs, list two advantages and two disadvantages of plain sawing compared to quarter sawing.
Pupils’ Activity: Pupils work in pairs to discuss and write down their answers.
Learning Point: Pupils apply their understanding of the conversion methods.

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 timber conversion?
State three advantages of timber conversion.
Mention three disadvantages of timber conversion.
Briefly compare plain sawing and quarter sawing methods.

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, re-emphasizing the importance of understanding timber conversion for furniture making. The teacher assigns homework: “Draw and label two different methods of timber conversion.”
Pupils’ Activity: Pupils listen to the summary and copy down the homework.
Learning Point: Pupils consolidate their learning and are given a task to reinforce understanding.

Lesson Keywords

Timber Conversion – The process of sawing felled logs into usable sizes and shapes.
Plain Sawing – A timber conversion method that cuts through the log, yielding varied grain patterns and being prone to warping.
Quarter Sawing – A timber conversion method that produces stable boards with uniform grain patterns, less prone to warping.
Seasoning – The process of drying timber to remove moisture, making it suitable for use.
Warping – The distortion of timber from its true shape, often caused by uneven drying.

Differentiation

For pupils who grasp concepts quickly, the teacher can ask them to research other less common timber conversion methods. For pupils needing more support, the teacher will provide simplified diagrams and allow for more peer-assisted learning during the activity sections.

Note for teachers using this lesson plan

Ensure that the timber samples for demonstration are clearly labelled for each conversion method to avoid confusion. Encourage pupils to relate the concepts to practical applications in their local environment. Safety precautions should always be discussed when handling timber samples or discussing woodworking tools.