Lesson Notes By Weeks and Term v3 - Senior Secondary 3
Construction of different items of furniture
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Construction of different items of furniture
Download the Lessonotes Mobile Nigeria 2025 app for faster lesson access on Android and iPhone.
Subject: Furniture Making
Class: Senior Secondary 3
Term: 2nd Term
Week: 4
Theme: Furniture Design
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Prepared materials for construction. Set-out joints and shapes. Cut joints and shapes. As semble – parts of the Joints. Carry out the finishing.
This section provides a detailed breakdown of the practical steps involved in furniture construction, covering each performance objective.
A. Preparation of Materials for Construction: This initial stage is critical for ensuring accuracy, efficiency, and quality in the final product.
1. Understanding the Design/Drawing: Before any physical work begins, the construction drawing or sketch of the furniture item (e.g., a simple stool, a small shelf, a bedside table) must be thoroughly understood. This includes dimensions, joint types, and material specifications.
2. Timber Selection and Preparation: Selection: Choose timber (e.g., Iroko, Mahogany, Obeche, Abura commonly used in Nigeria) that is free from major defects like large knots, shakes, twists, or fungal decay. Ensure the timber is well-seasoned to prevent warping or cracking after construction.
Dimensioning (Rough Sizing): Cut the timber to approximate lengths and widths slightly larger than the final required dimensions using a handsaw or circular saw. This allows for subsequent accurate planing.
Planing: Use a jack plane or surface planer to flatten one face (face side), then one edge (face edge) square to the face side. Mark these with a face side/edge mark (e.g., a pencil squiggle or triangle) for reference. Plane the remaining face and edge to the required thickness and width, ensuring they are parallel and square to the marked faces/edges.
Cross-cutting to Length: Cut the planed timber pieces to the exact final lengths specified in the cutting list, ensuring ends are square.
Cutting List Verification: Compare all prepared pieces against the cutting list to confirm correct dimensions and quantities.
3. Board Material Preparation (if applicable): For materials like plywood, MDF, or particle board, measure and mark out dimensions directly onto the board. Cut accurately using a handsaw, panel saw, or circular saw, ensuring straight edges and square corners. Edge banding may be applied later if needed.
B. Setting-out Joints and Shapes: Accuracy at this stage dictates the fit and strength of the joints.
1. Understanding the Joint: For effective instruction, focus on a common joint like the Mortise and Tenon joint (widely used in frame construction for chairs, tables) or a Dovetail joint (for drawers, boxes).
Mortise and Tenon Joint: This joint consists of a tenon (a projecting tongue) on one piece of timber that fits into a mortise (a rectangular hole) in another.
Dovetail Joint: A strong joint characterized by interlocking wedge-shaped 'tails' and 'pins'.
2. Tools for Setting Out: Steel rule, measuring tape, marking gauge, mortise gauge, try square, pencil (HB or H for fine lines), knife/marking knife.
3. Steps for Setting Out a Mortise and Tenon Joint (Example for a chair frame): Marking Shoulder Lines: On the piece to receive the tenon (e.g., the rail), use a try square and pencil/knife to mark the shoulder lines (where the tenon meets the rail) across the face and edges.
Marking Tenon Thickness (Cheek Lines): Set a marking gauge to half the thickness of the rail (assuming a centered tenon). From the face side, mark the cheek lines along both edges and ends of the tenon piece. Repeat from the opposite face side for a perfectly centered tenon.
Marking Tenon Length: Set the marking gauge to the desired tenon length (e.g., 20-30mm). Mark this distance from the end of the tenon piece, on both edges.
Marking Mortise Position and Width: On the piece to receive the mortise (e.g., the leg), measure and mark the exact position where the mortise will be. Set a mortise gauge to the tenon thickness (the distance between the cheek lines). Mark the mortise lines along the edges and ends of the mortise piece, ensuring they are centered and within the shoulder lines. Use a try square to mark the mortise end lines.
Waste Material Identification: Clearly mark the waste material areas with a cross or 'X' to avoid cutting the wrong part.
C. Cutting Joints and Shapes: This stage requires precision and control with hand tools or machinery.
1. Tools for Cutting Joints: Handsaws (tenon saw, dovetail saw), chisels (bevel-edge chisel, mortise chisel), mallet, coping saw (for curved shapes), bench vice or clamps. 2. *Steps for Cutting a Mortise and of the mortise piece, ensuring they are centered and within the shoulder lines. Use a try square to mark the mortise end lines.
Waste Material Identification: Clearly mark the waste material areas with a cross or 'X' to avoid cutting the wrong part.
C. Cutting Joints and Shapes: This stage requires precision and control with hand tools or machinery.
1. Tools for Cutting Joints: Handsaws (tenon saw, dovetail saw), chisels (bevel-edge chisel, mortise chisel), mallet, coping saw (for curved shapes), bench vice or clamps.
2. Steps for Cutting a Mortise and Tenon Joint: Cutting the Tenon: Shoulder Cuts: Place the tenon piece in a vice. Using a tenon saw, cut along the shoulder lines, ensuring the saw kerf is in the waste material. Cut from the face side first.
Cheek Cuts: Re-position the piece. Cut along the cheek lines down to the shoulder lines. The saw should be just outside the marked line (in the waste).
Waste Removal: Carefully remove the waste material, aiming for a clean, flat surface.
Cutting the Mortise: Boring (Optional): For deep mortises, bore out the bulk of the waste with an auger bit or drill bit, staying within the mortise lines.
Chiseling: Use a mortise chisel (or a bevel-edge chisel for shallower mortises) and a mallet. Start chiseling about 3mm inside one end line, working towards the center. Turn the chisel around and work from the other end. Gradually deepen the mortise, chopping out small amounts of waste material. Ensure the sides are straight and the bottom is flat. Periodically check the mortise size with the tenon.
3. Cutting Shapes: Curved Shapes: Use a coping saw for internal curves or a bow saw/band saw for external curves. Carefully follow the marked line, cutting just outside it. Refine the shape with rasps, files, and sandpaper.
Recesses/Rebates: Use a rebate plane or router for cutting rebates. For dadoes (grooves across the grain), use a dado plane or router.
D. Assembly – Parts of the Joints: This involves fitting the components together securely.
1. Dry Assembly: Before applying glue, always perform a dry assembly. This means fitting the joint together without glue to check for fit, squareness, and overall alignment of the furniture piece. Adjustments can be made at this stage (e.g., paring with a chisel for a snug fit). A well-fitting joint should go together with firm hand pressure or light tapping with a mallet.
2. Glue Application: Choose an appropriate wood adhesive (e.g., PVA wood glue, often called "Topbond" or similar brands in Nigeria, or contact adhesive for laminates). Apply a thin, even layer of glue to both mating surfaces of the joint (e.g., inside the mortise and on the tenon cheeks). Avoid excessive glue, which can squeeze out and create finishing problems.
3. Final Assembly: Carefully bring the glued components together. Use a mallet and a block of wood to gently tap the joints fully home.
Check for Squareness: Immediately after assembly, use a large try square or framing square to check all corners for squareness. Use clamps or sash cramps to hold the assembly firmly until the glue cures. For frames, apply clamps in both directions if necessary.
Clean Excess Glue: Wipe off any squeezed-out glue with a damp cloth before it dries hard.
4. Clamping and Drying: Leave the assembled item clamped until the glue has fully cured (refer to glue manufacturer's instructions, typically 2-6 hours, full strength in 24 hours).
E. Carry out the Finishing: Finishing enhances the appearance, protects the wood, and prolongs the life of the furniture.
1. Surface Preparation: Sanding: Begin sanding with a coarser grit sandpaper (e.g., P80 or P100) to remove tool marks and scratches. Work progressively through finer grits (e.g., P120, P150, P180, P220) until the surface is smooth to the touch. Always sand in the direction of the wood grain.
Dust Removal: Thoroughly remove all sanding dust using a brush, vacuum, or tack cloth before applying any finish.
Filling: Fill any small holes, cracks, or minor defects with wood filler matching the timber colour. Allow to dry, then sand the furniture.
1. Surface Preparation: Sanding: Begin sanding with a coarser grit sandpaper (e.g., P80 or P100) to remove tool marks and scratches. Work progressively through finer grits (e.g., P120, P150, P180, P220) until the surface is smooth to the touch. Always sand in the direction of the wood grain.
Dust Removal: Thoroughly remove all sanding dust using a brush, vacuum, or tack cloth before applying any finish.
Filling: Fill any small holes, cracks, or minor defects with wood filler matching the timber colour. Allow to dry, then sand smooth.
2. Types of Finishes (Common in Nigeria): Varnish: Provides a durable, protective, clear or tinted coating. Available in gloss, satin, or matt.
Lacquer: Dries quickly, offers a hard-wearing finish, often sprayed on.
Wood Stain: Changes the colour of the wood without obscuring the grain. Applied before a clear topcoat (varnish/lacquer). Wood Polish (Wax Polish, Spirit Polish/French Polish): Traditional finishes that enhance natural grain, offer less protection than varnish but give a classic feel.
Paint: Provides an opaque colour finish, used when the wood grain is not desired or for cheaper timber.
3. Application Methods: Brushing: Common for varnish, paint, and some stains. Apply thin, even coats, brushing in the direction of the grain. Allow adequate drying time between coats and light sand with fine grit paper (e.g., P220) between coats for better adhesion and smoothness.
Spraying: Used for lacquer and some paints, provides a very smooth, even finish. Requires special equipment and ventilation.
Wiping: Used for some oil finishes or wipe-on varnishes. Applied with a clean cloth, wiped on, and excess wiped off.
Rubbing: For wax polishes, applied with a cloth and buffed to a sheen.
4. Final Inspection: After the final coat has dried and cured, inspect the furniture for any imperfections, ensure all surfaces are smooth, and the finish is even.
Teacher Activities: Introduction & Review: Begin by reviewing previous knowledge on tools, materials, and joint types. Connect these to the current topic of furniture construction.
Safety Briefing: Emphasize workshop safety rules, especially concerning the use of hand tools (saws, chisels, planes) and power tools (if available). Proper handling, personal protective equipment (PPE) like safety glasses, and maintaining a clean workspace.
Demonstration: Material Preparation: Demonstrate proper timber selection, identifying defects. Show how to measure, mark, and dimension timber accurately (rough cutting, planing face side/edge, then thickness/width, cross-cutting). Explain the concept of a cutting list.
Demonstration: Setting Out Joints and Shapes: Choose a specific joint (e.g., Mortise and Tenon or Dovetail). Perform a step-by-step demonstration of marking out the chosen joint on actual timber pieces, explaining the use of each tool (marking gauge, try square, pencil/knife) and the rationale behind each line. Demonstrate marking out a simple curve or shaped edge.
Demonstration: Cutting Joints and Shapes: Demonstrate the correct and safe use of appropriate saws (tenon saw, dovetail saw) for cutting shoulders and cheeks for the tenon. Demonstrate the safe and effective use of chisels and mallet for cutting the mortise, emphasizing correct grip, striking, and waste removal. Show how to use a coping saw or bow saw to cut a curved shape.
Demonstration: Assembly: Perform a dry assembly of the prepared joint/components. Point out common fitting issues and how to rectify them (e.g., paring with a chisel). Demonstrate proper glue application. Demonstrate the final assembly process, checking for squareness, and the correct use of clamps/sash cramps. Show how to clean up excess glue.
Demonstration: Finishing: Demonstrate the sanding process using progressive grits, explaining the purpose of each grit. Show how to apply wood filler. Demonstrate the application of a common finish (e.g., varnish or wood stain + varnish) using a brush, emphasizing thin, even coats and grain direction.
Supervision and Guidance: Circulate among students during practical activities, providing individual feedback, correcting techniques, and ensuring safety adherence.
Q&A Session: Encourage questions throughout the demonstrations and practical work.
Student Activities: Active Observation: Closely observe teacher demonstrations, taking notes on procedures, tool usage, and safety precautions.
Practical Work: Material Preparation: Working individually or in small groups, select and prepare timber pieces according to a provided cutting list for a small project (e.g., a simple wooden box, a stool leg assembly). Practice measuring, marking, planing (if tools are available and supervised), and cross-cutting to dimensions.
Practical Work: Setting Out Joints and Shapes: On the prepared timber pieces, practice setting out the chosen joint (e.g., Mortise and Tenon) and a simple shape (e.g., a curved top edge for a stool). Students use marking gauges, try squares, and pencils to accurately mark all lines.
Practical Work: Cutting Joints and Shapes: Under strict supervision, students practice cutting the marked joints and shapes using appropriate hand tools (tenon saw, chisels, mallet, coping saw). Emphasis on precision, safety, and controlled movements.
Practical Work: Assembly: Students perform dry assembly of their cut components to check fit. Apply glue and assemble their components, using clamps to hold the joint securely while checking for squareness. Clean up excess glue.
Practical Work: Finishing: Students sand their assembled components or a pre-prepared sample piece through progressive grits. Apply wood filler if necessary. Practice applying a chosen finish (e.g., varnish) with a brush, ensuring even coverage and smooth finish.
Group Discussion: Discuss challenges faced during practical work and share best practices.
Entrepreneurship and Local Industry Development: The skills learned in constructing furniture are directly applicable to starting small-scale furniture businesses (e.g., making bespoke chairs, tables, cabinets for clients in communities, schools, or offices). Many successful furniture makers in Nigeria started by mastering these fundamental construction techniques. This reduces dependence on imported furniture, boosts local manufacturing, and creates employment opportunities for youth and artisans.
Home Improvement and Self-Sufficiency: Individuals with these skills can construct or repair their own household furniture, reducing expenses and fostering a sense of self-reliance. For example, a student can make a shoe rack, a bookshelf, or repair a broken chair leg at home, integrating woodworking into daily life and saving money that might have been spent on a carpenter or new item.
Community Development Projects: Skilled furniture makers can contribute to community projects, such as making desks and benches for local schools, pews for churches, or furniture for health centres. This provides practical skills that directly serve societal needs and build community infrastructure using local resources.