Class: Senior Secondary School 1 (SS1 / SSS1)
Term: 2nd Term
Week: 4
Age: 15 years
Duration: 45 minutes
Subject: Furniture Making
Curriculum Theme: Trade
Previous Lesson: Classification Of Timber: Types And Characteristics.
Topic: Conversion Of Timber
Subject Matter: Meaning of timber conversion, Conversion methods, Timber processing stages

Specific Objectives

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

Cognitive Domain:

Define timber conversion.
List at least three methods of timber conversion.
Explain the stages involved in timber processing after conversion.

Affective Domain:

Appreciate the importance of proper timber conversion techniques.
Value the different methods used in converting timber.

Psychomotor Domain:

Identify different types of converted timber based on sawing methods.
Sketch simple diagrams illustrating timber conversion methods.

Discuss with peers the advantages and disadvantages of various conversion methods.
Collaborate in identifying tools used in timber conversion.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Basic Technology (Junior Secondary)
State Unified Scheme of Work for Furniture Making (Senior Secondary)
Basic Technology for Senior Secondary Schools, Book 1
https://www.wood-database.com/wood-articles/quarter-sawn-vs-flat-sawn/
https://www.wood-database.com/wood-articles/drying-and-seasoning-wood/

Instructional Materials

The teacher will teach this lesson with the aid of:

Sawmill blades
Timber logs (real or pictures)
Charts showing different timber conversion methods
Diagrams of timber processing stages

Rationale for the Lesson

This lesson helps pupils understand how raw timber logs are transformed into usable lumber for furniture making. Knowing the different conversion methods enables pupils to select appropriate timber for specific projects and appreciate the quality of finished wood products.

Prerequisite/Previous Knowledge

Pupils have some basic knowledge of different types of timber and their uses.

Lesson Content/Board Summary

Conversion of Timber

Meaning of Timber Conversion

Timber conversion is the process of cutting down felled trees (logs) into various usable sizes and shapes of lumber or planks. This process prepares the timber for further processing and use in construction or furniture making.

Methods of Timber Conversion

There are different methods used to convert timber, each with its own advantages regarding grain pattern, stability, and waste. The common methods include:

Through and Through Sawing (Plain Sawing/Flat Sawing): The log is cut into planks by making parallel cuts across its entire length without turning the log. This method is fast and produces wide planks with distinct grain patterns but can result in more warping and cupping.
Quarter Sawing: The log is first cut into quarters, and then each quarter is sawn radially (from the center outwards). This method produces highly stable timber with attractive grain patterns (medullary rays) but is slower and results in more waste.
Tangential Sawing (Back Sawing): Similar to plain sawing but the log might be turned to get specific grain patterns. It is not as common as a primary method for structural timber but can be used for decorative purposes.
Radial Sawing: Similar to quarter sawing, where cuts are made from the center to the circumference. It produces very stable timber but is complex and has high waste.

Timber Processing Stages

After conversion, timber undergoes further processing to make it suitable for use. These stages improve its stability, durability, and workability. The main stages are:

Seasoning: This is the process of reducing the moisture content in timber to an acceptable level.
- Air Seasoning: Timber is stacked in open sheds, allowing air to circulate and gradually dry the wood over several months or years.
- Kiln Seasoning: Timber is dried in controlled chambers (kilns) using heat and humidity, which is a faster process than air seasoning.
Planing: After seasoning, timber is passed through a planing machine to smooth its surfaces and achieve precise dimensions. This makes the wood ready for joinery and finishing.
Preservation: This involves treating timber with chemicals to protect it against pests (insects, termites) and fungi (rot). Common methods include pressure treatment or surface application of preservatives.
Storage: Properly processed timber needs to be stored in dry, well-ventilated areas, away from direct sunlight and moisture, to maintain its quality and prevent damage before use.

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 identify common wooden items in the classroom (e.g., desks, chairs, door frames). The teacher then asks how they think these items are made from raw tree trunks.
Pupils’ Activity: Pupils identify wooden items and attempt to answer the question, linking it to cutting trees.
Learning Point: Pupils recall prior knowledge and are introduced to the concept of processing timber.

Step 2: Meaning of Timber Conversion

Time: 7 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines timber conversion as the process of cutting felled trees into usable sizes. The teacher uses a log (or picture) to illustrate how it is cut into planks.
Pupils’ Activity: Pupils listen attentively, take notes, and ask questions for clarification.
Learning Point: Pupils understand the definition of timber conversion.

Step 3: Methods of Timber Conversion

Time: 12 minutes
Teaching Skill: Illustration/Discussion
Teacher’s Activity: The teacher explains and sketches the different methods of timber conversion on the board: Through and Through Sawing, Quarter Sawing, Tangential Sawing, and Radial Sawing. The teacher uses charts or diagrams to show the grain patterns resulting from each method and briefly discusses their characteristics.
Pupils’ Activity: Pupils observe the sketches and diagrams, identify the methods, and participate in a brief discussion about them.
Learning Point: Pupils learn about and can identify various methods of timber conversion.

Step 4: Timber Processing Stages

Time: 10 minutes
Teaching Skill: Explanation/Listing
Teacher’s Activity: The teacher explains the subsequent stages of timber processing after conversion, including seasoning (air and kiln), planing, preservation, and storage. The teacher emphasizes the importance of each stage.
Pupils’ Activity: Pupils listen, take notes, and ask questions about the processing stages.
Learning Point: Pupils understand the steps involved in preparing timber for use.

Step 5: 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?
Mention three methods of timber conversion.
List two types of seasoning.
State one importance of planing timber.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 6: Conclusion

Time: 6 minutes
Teaching Skill: Summarization/Assignment
Teacher’s Activity: The teacher summarizes the key points of the lesson, reiterating the importance of proper timber conversion and processing. The teacher gives an assignment to research specific tools used in a sawmill.
Pupils’ Activity: Pupils listen to the summary and copy the assignment.
Learning Point: Pupils consolidate their understanding and are given further learning tasks.

Lesson Keywords

Timber Conversion – The process of cutting logs into usable lumber.
Plain Sawing – A method of cutting logs into planks by making parallel cuts.
Quarter Sawing – A method where logs are cut into quarters then sawn radially for stability.
Seasoning – Reducing moisture content in timber to prevent warping and decay.
Planing – Smoothing timber surfaces to achieve precise dimensions.

Differentiation

For pupils who grasp concepts quickly, the teacher can ask them to compare the cost-effectiveness and environmental impact of different conversion methods. For pupils needing more support, the teacher can provide simplified diagrams and allow them to work in pairs to identify the methods and stages.

Note for teachers using this lesson plan

Ensure to bring visual aids like actual wood samples or detailed pictures of different cuts (plain sawn, quarter sawn) and processing stages. Emphasize safety precautions in sawmills if discussing industrial processes. Encourage pupils to relate the concepts to everyday wooden items.