Lesson Notes By Weeks and Term v4 - SHS 1
WELDING TECHNOLOGY
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WELDING TECHNOLOGY
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Subject: Applied Technology
Class: SHS 1
Term: 2nd Term
Week: 8
Grade code: 1.4.1.LI.2
Strand code: 4
Sub-strand code: 2
Content standard code: 1.4.1.CS.1
Indicator code: 1.4.1.LI.2
Theme: METAL TECHNOLOGY
Subtheme: WELDING TECHNOLOGY
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This lesson introduces the foundational hand tools used in metalwork and welding technology. Before any welding can happen, a metalworker must be able to measure accurately, mark out designs precisely, hold the workpiece securely, cut it to the correct size, and sometimes shape it with striking tools. These skills are essential for creating strong, safe, and professional-looking metal products. In Ghana, from the gates and burglar proofs on our homes to the metal frames of market stalls and the repair of tro-tros, these fundamental tools are used every single day by skilled artisans. Mastering their use is the first step to becoming a competent welder or metal fabricator.
This section covers the five main categories of hand tools used in preparing metal for welding. Category 1: Measuring Tools These tools are used to determine the dimensions (length, width, thickness, angles) of a workpiece. Accuracy here is crucial; a small mistake in measurement can ruin the entire project. Tool 1: Steel Rule Description: A flat, rigid ruler made of steel, with markings for millimetres (mm), centimetres (cm), and sometimes inches. They are more durable and accurate than wooden or plastic rulers for metalwork. Use: For making short, precise linear measurements on flat metal surfaces. It is also used as a straight edge for marking lines with a scriber. Ghanaian Context: A welder making a window frame will use a steel rule to measure and re-check the lengths of the small metal bars before cutting and welding them together. Safety: The edges can be sharp. Handle with care to avoid cuts. Tool 2: Measuring Tape Description: A flexible, retractable tape made of metal or fibreglass, housed in a plastic or metal case. They come in various lengths (e.g., 3m, 5m, 30m). Use: For measuring longer lengths and curved surfaces where a rigid steel rule cannot be used. Ghanaian Context: Used by fabricators to measure the dimensions of a gate opening at a client's house or the total length of steel rod needed for a roofing truss project. Safety: Allow the tape to retract slowly; letting it fly back can cause injury or damage the hook at the end. Category 2: Marking Out Tools These tools are used to transfer dimensions from a plan onto the metal workpiece. They create clear lines or points to guide cutting, drilling, or bending. Tool 1: Scriber Description: A pen-like tool with a very sharp, hardened steel point. Use: To scratch or scribe fine, accurate lines onto a metal surface. It creates a much thinner and more precise line than a pencil or pen, which would rub off easily. It is used with a steel rule or try square as a guide. Ghanaian Context: After measuring a piece of sheet metal for a "chop box," a fabricator uses a scriber to mark the exact cutting lines. Safety: The point is extremely sharp. Always replace the protective cap when not in use and never carry it in your pocket with the point exposed. Tool 2: Centre Punch Description: A short steel rod with a conical (cone-shaped) point. Use: To make a small indentation or "dot" in a metal surface. This dot serves two purposes: (1) It marks the exact centre of a hole to be drilled, preventing the drill bit from "wandering." (2) It can be used for permanent marking points. It is struck with a hammer. Ghanaian Context: Before drilling holes in a metal post to attach hinges for a gate, a welder uses a centre punch to mark the hole locations. Safety: Hold the punch firmly and ensure your fingers are out of the hammer's path. Wear safety goggles to protect against flying metal fragments. Tool 3: Try Square Description: An L-shaped tool consisting of a thick, heavy stock and a thinner, longer blade, set at a perfect 90-degree angle. Use: Used for two main jobs: (1) Marking out lines that are perpendicular (at 90°) to an edge. (2) Checking if corners and edges are "square" (exactly 90°). Ghanaian Context: Essential for making rectangular frames for burglar proofs, ensuring all four corners are perfect right angles for a professional fit. Safety: Avoid dropping it, as this can knock it out of square and make it useless for accurate work. Category 3: Holding Tools These tools are used to grip and hold the workpiece securely while it is being worked on. This is vital for both safety and accuracy. Tool 1: Bench Vice Description: A large, heavy mechanical device bolted to a workbench. It has two jaws—one fixed and one that moves by turning a handle—to clamp a workpiece tightly. Use: To hold metal firmly in place for operations like sawing, filing, or drilling. Ghanaian Context: Almost every metalwork shop in Kokompe or Suame Magazine has a bench vice. It's used to hold a metal rod while it's being cut with a hacksaw. Safety: Do not overtighten, as this can damage the workpiece or the vice. Ensure the vice is securely bolted to the bench before use. Tool 2: G-Clamp (or C-Clamp) Description: A portable clamp shaped like the letter 'G' or 'C'. It has a screw thread that tightens a jaw against a fixed frame. Use: To hold pieces of metal together for welding or to clamp a workpiece onto a bench or drill press table when a vice is not suitable. Ghanaian Context: A welder might use two G-clamps to hold two metal plates together in the correct position while they perform the initial "tack" welds. Safety: Use a piece of scrap wood between the clamp and the workpiece to prevent the clamp from leaving marks. Category 4: Striking Tools These tools are used to deliver impact force for tasks like shaping metal, driving punches, or riveting. Tool 1: Ball Pein Hammer Description: A hammer with two heads. One face is flat for general striking, and the other is a round, ball shape (the "peen") for shaping metal. Use: The flat face is used for striking punches and chisels. The ball peen is used for shaping metal, such as rounding the ends of rivets or creating decorative textures (peening). Ghanaian Context: A blacksmith uses the ball peen side to shape hot metal, and a mechanic uses the flat face to strike a centre punch. Safety: Ensure the hammer head is securely fixed to the handle. Always wear safety goggles. Grip the handle near the end for maximum control and power. Tool 2: Mallet Description: A hammer-like tool with a large head made from a softer material like wood, rubber, or plastic. Use: Used for striking materials when you do not want to leave a mark or damage the surface. It is used to shape soft sheet metal or to tap pieces into place without denting them. Ghanaian Context: An artisan making aluminium cooking pots or utensils would use a mallet to shape the sheet metal without cracking or marking it. Safety: Use the correct type of mallet for the job (e.g., don't use a wooden mallet on a sharp metal edge as it will splinter). Category 5: Cutting Tools These tools are used to remove material and cut the workpiece to the desired size and shape. Tool 1: Hacksaw Description: A fine-toothed saw with a C-shaped frame that holds a thin, replaceable blade under tension. Use: For cutting metals like steel rods, pipes, and bars. The blade's teeth should point away from the handle, as it cuts on the forward stroke. Ghanaian Context: This is the most common hand tool for cutting metal rods to size for making everything from burglar proofs to metal stands for coal pots. Safety: Ensure the blade is tensioned correctly (it should make a "ping" sound when plucked). A loose blade can buckle and break. Always wear safety goggles. Tool 2: Tin Snips (Aviation Snips) Description: A pair of scissors designed for cutting thin sheet metal. They have short blades and long handles to provide leverage. Some come with colour-coded handles for cutting straight, left, or right curves. Use: For cutting sheet metal (e.g., roofing sheets, metal for car body repairs). They are not suitable for thick metal rods or bars. Ghanaian Context: Roofers use tin snips to cut corrugated iron sheets to fit around vents or at the edge of a roof. Safety: Very sharp. Keep fingers clear of the blades. Wear gloves to protect against the sharp edges of the cut metal.
Guided Practice (With Solutions)
Instructions: Work in your groups to answer the following questions. We will discuss the answers as a class.
Question 1: You are given the following tools: Hacksaw, Steel Rule, Bench Vice, Centre Punch, Mallet. Place each tool into its correct category in the table below.