Lesson Notes By Weeks and Term v4 - SHS 1
ENGINEERING MATERIALS, TOOLS AND MACHINES
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ENGINEERING MATERIALS, TOOLS AND MACHINES
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Applied Technology
Class: SHS 1
Term: 2nd Term
Week: 6
Grade code: 1.4.1.LI.2
Strand code: 4
Sub-strand code: 1
Content standard code: 1.4.1.CS.1
Indicator code: 1.4.1.LI.2
Theme: METAL TECHNOLOGY
Subtheme: ENGINEERING MATERIALS, TOOLS AND MACHINES
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This lesson introduces you to the fundamental hand tools used in metalwork. In Ghana, from the local welder in your community making burglar-proof windows to the mechanic at Abossey Okai fixing cars, these tools are used every day. Understanding the correct tool for each job is the first step to becoming a skilled technician. Using the wrong tool can damage your project, damage the tool itself, and most importantly, cause serious injury. This lesson will equip you with the foundational knowledge to identify, categorise, and explain the use of the most common tools in the workshop, ensuring you can work safely and efficiently.
In any metalwork project, we follow a sequence of operations. We first measure the material, then we mark where we need to work, hold it securely, and finally perform operations like cutting or shaping. Each step requires a specific category of tools. A. Measuring Tools These tools are used to determine the dimensions (length, width, thickness, diameter, angles) of a workpiece. Accuracy starts with correct measurement. Steel Rule: Description: A flat strip of steel with graduated markings (usually in millimetres and centimetres on one edge, and inches on the other). Use: For taking linear measurements (measuring straight lines). It is the most common measuring tool in the workshop. Ghanaian Context: A carpenter uses a steel rule to measure the length of a metal tube needed to frame a small 'container' shop. Try Square: Description: Consists of two parts at a fixed 90° angle: a thick wooden or metal stock and a thinner steel blade. Use: To check for "squareness" (perfect 90° angles) on corners of a workpiece. To mark lines at 90° to a straight edge. To check if a surface is flat. Ghanaian Context: A welder making a metal gate uses a try square to ensure the corners of the frame are perfectly square before welding them together. Vernier Caliper: Description: A more complex-looking tool with a fixed jaw and a sliding jaw, along with a main scale and a vernier scale. Use: For making very precise measurements (up to 0.02mm) of an object's external diameter, internal diameter, and depth. Ghanaian Context: An engineering student at KNUST might use a vernier caliper to measure the precise diameter of a bolt for a university project. B. Marking Out Tools After measuring, you need to mark the dimensions onto the metal surface. These marks guide your cutting, drilling, or bending. Pencils are not used on metal as the lines rub off easily and are too thick for accuracy. Scriber: Description: A pen-like tool with a hardened, sharp steel point. Use: To scratch thin, accurate lines onto a metal surface. It is the "pencil" of metalwork. Ghanaian Context: A tinsmith marking out the shape for a "kyen-kyen-a" (metal sponge) on a sheet of metal would use a scriber. Centre Punch: Description: A short steel rod with a conical (cone-shaped) point, typically ground to 60° or 90°. Use: To make a small indentation or "dot" on a metal surface. This dot serves as a starting point for a drill bit, preventing it from "wandering" or slipping when you start drilling. Ghanaian Context: Before drilling a hole in a metal sheet to install a new lock on a door, the artisan first uses a centre punch to mark the exact spot. C. Holding Tools (Vices and Clamps) These tools are used to hold a workpiece securely and safely while you perform operations like sawing, filing, or drilling. Never hold a workpiece with your bare hands while working on it. Bench Vice (or Engineer's Vice): Description: A large, heavy vice that is bolted firmly to a workbench. It has two jaws (one fixed, one movable) that are tightened with a screw handle. Use: For holding heavy or large pieces of metal securely while performing tasks like sawing, filing, or chiselling. Ghanaian Context: Almost every mechanic's shop has a bench vice for holding engine parts or other components that need to be worked on. G-Clamp (or C-Clamp): Description: A G-shaped tool with a threaded screw. Use: For clamping pieces of metal together (e.g., for gluing or welding) or for holding a workpiece down onto a workbench or drill press table. Ghanaian Context: A furniture maker might use a G-clamp to hold two pieces of a metal chair frame together while the weld cools and sets. D. Striking Tools These tools are used to apply force to an object, often to shape metal, drive in a punch, or knock parts together or apart. Ball-pein Hammer: Description: A hammer with a flat face on one end and a rounded, ball-shaped "pein" on the other. Use: The flat face is used for general striking work, like hitting a chisel or a centre punch. The ball pein is used for shaping metal, such as forming rivet heads or creating rounded shapes (peening). Ghanaian Context: A blacksmith uses a ball-pein hammer to shape hot metal into tools or decorative items. Mallet: Description: A hammer-like tool with a large head made from a softer material than steel, such as rubber, wood, or plastic. Use: For striking materials without damaging their surface. It is used to shape soft sheet metal or to tap components into place without leaving marks. Ghanaian Context: A worker installing aluminum window frames might use a rubber mallet to gently tap the frames into place without denting the aluminum. E. Cutting Tools These tools are designed to remove material from a workpiece by shearing, sawing or chipping. Hacksaw: Description: A C-shaped frame that holds a thin, replaceable blade with fine teeth. The blade teeth must always point away from the handle. Use: For cutting metal rods, bars, pipes, and thick sheets. The cutting action happens on the forward stroke. Ghanaian Context: A plumber cutting a metal pipe to the correct length for a water connection uses a hacksaw. Cold Chisel: Description: A hardened steel bar with a sharp cutting edge at one end and a flat striking surface at the other. Use: Used with a hammer to cut or shear thick metal sheets, cut off rivet heads, or chip away unwanted metal. Ghanaian Context: A mechanic might use a cold chisel and a hammer to split a rusted nut that cannot be removed with a spanner. Tin Snips (or Aviation Shears): Description: Look like a strong pair of scissors with short, powerful blades. Use: For cutting thin sheets of metal (sheet metal), like those used for roofing or making metal trunks ("chop boxes"). They are not suitable for thick metal. Ghanaian Context: A roofer uses tin snips to cut corrugated iron sheets to the correct size when roofing a house.
Guided Practice (With Solutions)
Question 1: Imagine you need to drill a hole in the exact centre of a small, flat metal plate. Which two marking out tools would you need, and in what order would you use them? Explain why. Solution: First Tool: Scriber. You would first use a scriber (along with a steel rule) to draw two diagonal lines from corner to corner on the plate. The point where the lines cross is the exact centre. Second Tool: Centre Punch. You would place the tip of the centre punch exactly on the intersection of the scribed lines and give it a firm tap with a ball-pein hammer. Commentary: This question tests your ability to select the right tools for a specific sequence. The scriber is needed for the accuracy of the line, and the centre punch is crucial to create a starting divot for the drill bit, ensuring the hole is drilled precisely at the centre.
Question 2: A welder wants to cut a 50cm length from a long, solid steel rod that is 15mm thick. Which measuring tool and which cutting tool should they use? Justify your choices. Solution: Measuring Tool: Steel Rule. A steel rule is perfect for measuring a 50cm linear distance on the rod accurately. Cutting Tool: Hacksaw. A hacksaw is the appropriate tool for cutting through a solid 15mm steel rod. A tool like tin snips would be completely ineffective as it is designed for thin sheets. A cold chisel could work but would leave a much rougher finish. Commentary: This question assesses your ability to match the tool's capability to the material's properties (thickness and type). It highlights the difference between cutting thin sheets and thick rods.