Class: Senior Secondary School 1 (SSS 1)
Term: 2nd Term
Week: 4
Age: 15 years
Duration: 45 minutes
Subject: Carpentry And Joinery
Curriculum Theme: Entrepreneurship Trade Subjects
Previous Lesson: Growth and Structure of Timber.
Topic: TIMBER – Timber Conversion
Subject Matter: methods of timber conversion, plain sawing, quarter sawing, rift sawing

Specific Objectives

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

Cognitive Domain:

Define timber conversion.
State three methods of timber conversion.
Explain the process of plain sawing, quarter sawing, and rift sawing.

Affective Domain:

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

Psychomotor Domain:

Sketch the different types of timber conversion methods.

Participate actively in class discussions regarding timber conversion.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Carpentry and Joinery
State Unified Scheme of Work for Senior Secondary Schools
Carpentry and Joinery for Senior Secondary Schools by A.O. Ojo

Instructional Materials

The teacher will teach this lesson with the aid of:

Charts illustrating timber conversion methods
Small pieces of timber (logs and sawn planks)
Whiteboard/Blackboard
Markers/Chalk

Rationale for the Lesson

This lesson helps pupils understand how raw timber logs are processed into usable forms for construction and furniture making. Knowing different conversion methods enables them to choose appropriate timber based on its properties and intended use, which is important for quality workmanship in carpentry and joinery.

Prerequisite/Previous Knowledge

Pupils are assumed to have basic knowledge of timber as a material and its general uses in carpentry.

Lesson Content/Board Summary

TIMBER CONVERSION

Definition of Timber Conversion

Timber conversion is the process of sawing logs into usable sizes and shapes of lumber (planks, boards, scantlings) for various construction and carpentry purposes.

Methods of Timber Conversion

There are different methods of converting logs into lumber, each with its advantages and disadvantages regarding yield, stability, and grain pattern. The common methods include:

Plain Sawing (also known as Through and Through Sawing or Flat Sawing)
Quarter Sawing
Rift Sawing

Plain Sawing (Through and Through Sawing/Flat Sawing)

Plain sawing is the simplest and most economical method of timber conversion. The log is cut into parallel planks along its length without turning. This method produces the highest yield of timber from a log.

Characteristics of plain sawn timber:

Produces wider planks.
Displays a pronounced growth ring pattern (cathedral pattern) on the face.
Is more susceptible to warping, twisting, and cupping due to tangential shrinkage.
Is generally less stable than quarter-sawn timber.

Quarter Sawing

Quarter sawing involves first cutting the log into quarters lengthwise, then sawing each quarter radially. The saw cuts are made roughly perpendicular to the growth rings.

Characteristics of quarter sawn timber:

Produces narrower planks.
Shows a straight, uniform grain pattern (medullary rays may be visible).
Is more stable and resistant to warping, twisting, and cupping.
Exhibits less shrinkage and swelling across the width.
Has a higher cost due to more waste and labor involved.

Rift Sawing

Rift sawing is a specialized method that produces timber with a very straight and consistent grain pattern. The log is cut at an angle of 30 to 60 degrees to the growth rings, often requiring multiple turns of the log.

Characteristics of rift sawn timber:

Possesses an extremely straight grain pattern.
Offers the highest stability and resistance to warping, twisting, and cupping.
Is the most expensive method due to significant waste and complex cutting.
Is often used for high-quality furniture, flooring, and architectural millwork where stability and appearance are paramount.

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 reminds them of the previous lesson on timber. The teacher then asks questions like, “What happens to a log after it is felled from a tree before it can be used for furniture?” and “How do we get planks from a log?”. This leads to the topic of timber conversion.
Pupils’ Activity: Pupils respond to questions and listen attentively.
Learning Point: Pupils recall previous knowledge and are introduced to the lesson topic.

Step 2: Explanation of Timber Conversion

Time: 10 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher explains the meaning of timber conversion, using the chart to show a log being cut into planks. The teacher also introduces the main methods of timber conversion.
Pupils’ Activity: Pupils listen, observe the chart, and take notes.
Learning Point: Pupils understand the definition and purpose of timber conversion.

Step 3: Plain Sawing

Time: 7 minutes
Teaching Skill: Demonstration/Explanation
Teacher’s Activity: The teacher explains plain sawing, demonstrating with a small log or drawing on the board how cuts are made parallel to each other. The teacher highlights the characteristics of plain sawn timber.
Pupils’ Activity: Pupils observe the demonstration, ask questions, and take notes.
Learning Point: Pupils understand the process and characteristics of plain sawing.

Step 4: Quarter Sawing

Time: 7 minutes
Teaching Skill: Demonstration/Explanation
Teacher’s Activity: The teacher explains quarter sawing, demonstrating how the log is first quartered and then sawn radially. The teacher discusses the unique characteristics of quarter sawn timber.
Pupils’ Activity: Pupils observe the demonstration, participate in discussions, and take notes.
Learning Point: Pupils understand the process and characteristics of quarter sawing.

Step 5: Rift Sawing

Time: 7 minutes
Teaching Skill: Demonstration/Explanation
Teacher’s Activity: The teacher explains rift sawing, illustrating the complex cutting angles involved to achieve a straight grain. The teacher emphasizes the high stability and cost of rift sawn timber.
Pupils’ Activity: Pupils observe the demonstration, ask clarifying questions, and take notes.
Learning Point: Pupils understand the process and characteristics of rift sawing.

Step 6: Class Activity/Sketching

Time: 4 minutes
Teaching Skill: Practical Application
Teacher’s Activity: The teacher instructs pupils to sketch the different methods of timber conversion in their notebooks, using the charts as a guide.
Pupils’ Activity: Pupils sketch the various timber conversion methods.
Learning Point: Pupils practice drawing and visualize 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:

Define timber conversion.
List three common methods of timber conversion.
Explain the process of plain sawing.
State two characteristics of quarter sawn timber.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 5 minutes
Teaching Skill: Summarization/Consolidation
Teacher’s Activity: The teacher summarizes the key points of the lesson, reiterating the importance of understanding different timber conversion methods. The teacher then gives pupils homework to research other factors affecting timber quality after conversion.
Pupils’ Activity: Pupils listen to the summary and copy down the homework assignment.
Learning Point: Pupils consolidate their learning and prepare for further study.

Lesson Keywords

Timber Conversion – The process of sawing logs into usable forms like planks and boards.
Plain Sawing – A method where logs are cut into parallel planks without turning.
Quarter Sawing – A method where logs are first quartered, then sawn radially.
Rift Sawing – A specialized method involving cutting logs at angles to the growth rings for straight grain.
Lumber – Timber that has been sawn into planks or boards.

Differentiation

For pupils who grasp concepts quickly, the teacher can provide additional examples of specific timber applications for each conversion method. For those who need more support, the teacher can offer individual guidance during the sketching activity and provide simplified diagrams.

Note for teachers using this lesson plan

Ensure that the charts used are clear and visually represent the cutting patterns for each conversion method. Hands-on demonstration with actual timber pieces, even small ones, can significantly enhance pupil understanding. Encourage pupils to ask questions and discuss the practical implications of each method.