Class: Senior Secondary School 1 (SS1 / SSS 1)
Term: 1st Term
Week: 9
Age: 15 years
Duration: 45 minutes
Subject: Machine Wood Work
Curriculum Theme: Technology
Previous Lesson: Properties Of Timber: Physical Properties Of Abura, Mahogany, Iroko And Opepe.
Topic: Timber Conversion
Subject Matter: Definition of timber conversion, Methods of timber conversion, Common market sizes of timber.

Specific Objectives

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

Cognitive Domain:

Define timber conversion.
State at least two methods of timber conversion.
List three common market sizes of timber.

Affective Domain:

Appreciate the importance of proper timber conversion.
Show interest in learning about wood processing techniques.

Psychomotor Domain:

Sketch one method of timber conversion.
Identify different market sizes of sawn timber.

Participate actively in class discussions.
Collaborate with peers to identify timber samples.

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 School 1 (Machine Wood Work).
Akinola, O. (2018). Basic Technology for Senior Secondary Schools Book 1. Learn Africa Plc.
https://www.wood-database.com/wood-articles/wood-basics-how-lumber-is-sawn/
https://www.britannica.com/technology/sawing

Instructional Materials

The teacher will teach this lesson with the aid of:

Samples of sawn timber (e.g., 2×4, 2×2).
Charts or pictures illustrating different sawmill operations and timber conversion methods.
Charts showing common market sizes of timber.

Rationale for the Lesson

Understanding timber conversion is important because it explains how raw logs are processed into usable materials for construction and furniture. This knowledge helps pupils appreciate the stages wood goes through before it is used and understand the different qualities of sawn timber available in the market.

Prerequisite/Previous Knowledge

Pupils are expected to have prior knowledge of different types of timber (hardwood and softwood) and the basic uses of wood.

Lesson Content/Board Summary

Timber Conversion

Definition of Timber Conversion

Timber conversion is the process of cutting logs (felled trees) into various usable sizes and shapes of sawn timber for different construction, carpentry, and joinery purposes.

Methods of Timber Conversion

There are several methods used to convert logs into sawn timber. These methods affect the stability, grain pattern, and amount of waste produced.

The following are common methods of timber conversion:

Plain Sawing (Through and Through Sawing): This is the simplest and most economical method. Logs are cut parallel to each other without turning. It produces wide boards but makes the timber more prone to warping and shrinking.
Quarter Sawing: This method involves cutting the log into quarters first, then sawing each quarter radially. It produces timber with stable dimensions and attractive grain patterns (medullary rays are visible), but it is more wasteful and expensive.
Tangential Sawing (Slash Sawing): In this method, the log is cut tangentially to the annual growth rings. It produces distinct “flame” grain patterns but the timber can be prone to cupping and twisting.
Radial Sawing: Similar to quarter sawing but involves more precise cuts directly from the center outwards. It yields very stable timber but is complex and results in significant waste.

Common Market Sizes of Timber

Sawn timber is available in various standard sizes in the market, typically measured in inches (imperial) or millimetres (metric). Lengths are also standardized.

The following are examples of common market sizes of timber:

1 inch x 1 inch (25mm x 25mm)
2 inches x 2 inches (50mm x 50mm)
2 inches x 3 inches (50mm x 75mm)
2 inches x 4 inches (50mm x 100mm)
3 inches x 4 inches (75mm x 100mm)
4 inches x 4 inches (100mm x 100mm)
Common lengths include 12 feet (3.6 metres), 16 feet (4.8 metres), and 18 feet (5.4 metres).

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 the previous lesson on types of timber. The teacher then displays a log and a piece of sawn timber, asking pupils how the log became the sawn timber.
Pupils’ Activity: Pupils respond to the teacher’s questions and observe the displayed materials.
Learning Point: Pupils connect previous knowledge to the new topic and are introduced to the concept of timber conversion.

Step 2: Definition of Timber Conversion

Time: 10 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines timber conversion, explaining that it is the process of cutting logs into usable sizes. The teacher writes the definition on the board.
Pupils’ Activity: Pupils listen attentively, ask questions for clarity, and copy the definition into their notebooks.
Learning Point: Pupils understand the meaning of timber conversion.

Step 3: Methods of Timber Conversion

Time: 10 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher explains and demonstrates the different methods of timber conversion (plain sawing, quarter sawing, tangential sawing) using charts and diagrams. The teacher highlights the characteristics and implications of each method.
Pupils’ Activity: Pupils observe the charts and diagrams, listen to the explanations, and ask questions about the methods.
Learning Point: Pupils identify and understand various methods of timber conversion.

Step 4: Common Market Sizes of Timber

Time: 7 minutes
Teaching Skill: Listing/Identification
Teacher’s Activity: The teacher presents samples of sawn timber and a chart showing common market sizes. The teacher names and describes the dimensions of various timber sizes and their typical lengths.
Pupils’ Activity: Pupils observe the timber samples and charts, identify the different sizes, and note them down.
Learning Point: Pupils recognize and list common market sizes of timber.

Step 5: Practical Identification and Sketching

Time: 5 minutes
Teaching Skill: Practical Application
Teacher’s Activity: The teacher guides pupils to sketch one of the timber conversion methods discussed. The teacher also asks pupils to pick up a timber sample and state its approximate size.
Pupils’ Activity: Pupils attempt to sketch a conversion method and identify the sizes of timber samples.
Learning Point: Pupils apply their knowledge by sketching and identifying timber sizes.

Step 6: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

Define timber conversion.
Mention two methods of timber conversion.
State one advantage of plain sawing.
List three common market sizes of timber.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 7: Conclusion

Time: 3 minutes
Teaching Skill: Summarization/Assignment
Teacher’s Activity: The teacher summarizes the key points of the lesson, emphasizing the importance of proper timber conversion for quality wood products. The teacher gives pupils an assignment to find out the uses of different timber sizes.
Pupils’ Activity: Pupils listen to the summary and copy the assignment.
Learning Point: Pupils consolidate their understanding and prepare for future learning.

Lesson Keywords

Timber Conversion – The process of cutting logs into usable sizes and shapes of sawn timber.
Plain Sawing – A method of timber conversion where logs are cut straight through without turning.
Quarter Sawing – A method where logs are first cut into quarters, then sawn radially.
Tangential Sawing – A method where logs are cut tangentially to the annual growth rings.
Sawn Timber – Wood that has been cut from logs into planks, boards, or beams.

Differentiation

For pupils who grasp concepts quickly, the teacher can challenge them to research the environmental impact of different conversion methods. For pupils needing more support, the teacher will provide simplified diagrams and offer one-on-one guidance during the sketching activity.

Note for teachers using this lesson plan

Ensure that the instructional materials, especially the timber samples and charts, are clear and visible to all pupils. Encourage active participation through questions and discussions. Emphasize the practical relevance of timber conversion in everyday life and industries.