Lesson Notes By Weeks and Term v3 - Senior Secondary 1
Measuring Instruments, Marking out Tools and Cuttings tools
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Measuring Instruments, Marking out Tools and Cuttings tools
Download the Lessonotes Mobile Nigeria 2025 app for faster lesson access on Android and iPhone.
Subject: Welding & Fabrication
Class: Senior Secondary 1
Term: 2nd Term
Week: 1
Theme: Tools In Fabrication And Welding
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Students should be able to name: Measuring In struments, Marking out to ols Cutting to ols
Measuring instruments are used to determine dimensions such as length, width, thickness, and angles of workpieces. Accuracy is paramount in fabrication to ensure components fit together correctly.
Steel Rule (Metal Rule): Description: A straight, flat strip of steel, usually 150mm (6 inches), 300mm (12 inches), 600mm (24 inches), or 1000mm (39 inches/1 metre) long, with graduations in millimetres (mm) and sometimes inches.
Function: Used for taking linear measurements, marking short distances, and checking flatness.
Application in Nigeria: Measuring the length of angle bars for a metal stand, checking the dimensions of a fabricated bracket for a generator, or measuring the width of a metal sheet for a water tank.
Tape Measure: Description: A flexible, retractable strip of metal or fabric, typically 3m, 5m, 8m, or 30m long, marked in millimetres, centimetres, and metres.
Function: Used for taking longer linear measurements, measuring curved surfaces, and laying out large dimensions.
Application in Nigeria: Measuring the perimeter of a metal fence installation, determining the length of roofing sheets, or marking out dimensions on large workpieces like vehicle chassis or fabrication tables.
Try Square: Description: An L-shaped tool with a steel blade fixed at 90 degrees to a stock (or beam), typically made of metal or wood.
Function: Used for checking squareness (90-degree angles) of workpieces, marking lines at right angles to an edge, and testing flatness over short distances.
Application in Nigeria: Ensuring the corners of a fabricated window frame are perfectly square, checking the perpendicularity of a weld joint on a gate, or marking a line perpendicular to the edge of a steel plate before cutting. Vernier Caliper (Brief mention for precision): Description: A precision measuring instrument capable of taking internal, external, depth, and step measurements, usually with an accuracy of 0.02mm or 0.05mm.
Function: For highly accurate measurements of small dimensions.
Application in Nigeria: Measuring the diameter of a shaft for a machine part, checking the thickness of thin sheet metal, or ensuring precise dimensions in custom fabrication for industrial clients. Micrometre (Brief mention for high precision): Description: An even more precise instrument than the Vernier caliper, typically used for measuring very small distances with accuracy up to 0.01mm.
Function: For extremely accurate measurements of thickness, diameter, and length.
Application in Nigeria: Used in specialized workshops for engine repairs (e.g., measuring crankshaft journals), precision tool and die making, or quality control in manufacturing. Marking out tools are used to transfer design dimensions onto the workpiece before cutting, bending, or drilling. Accurate marking-out is crucial for achieving desired finished dimensions.
Scriber (Marking Awl): Description: A steel rod with a hardened, sharp point at one or both ends, often knurled for grip.
Function: Used to scratch fine lines on metal surfaces, indicating points or lines for cutting, drilling, or bending. It provides a more permanent mark than a pencil or chalk.
Application in Nigeria: Marking cut lines on a steel plate for a custom bracket, drawing circles on a metal sheet for a drum lid, or transferring measurements from a drawing onto a workpiece.
Centre Punch: Description: A hardened steel rod with a sharp, conical point, usually ground to an angle of 90 degrees. It is struck with a hammer.
Function: Used to make small indentations (punch marks) on a metal surface. These marks serve as starting points for drilling, preventing the drill bit from "walking" off centre.
Application in Nigeria: Marking the exact centre of where a hole needs to be drilled on a metal plate for a bolt, creating punch marks along a scribed line for bending accuracy, or marking reference points for assembly.
Ball Peen Hammer (Engineer's Hammer): Description: A hammer with a hardened steel head, one face flat and the other hemispherical (ball peen).
Function: The flat face is used for general striking tasks, while the ball peen end is used for riveting, shaping metal, and particularly for striking the centre punch to create indentations.
Application in Nigeria: Striking a centre punch, shaping rivets when fabricating metal components, or light metal forming in panel beating.
Surface Gauge: Description: A tool consisting of a heavy base, an upright spindle, and a scriber holder that can be adjusted to various heights.
Function: Used for marking parallel lines at a specific height from a surface plate, checking height, or scribing lines on workpieces mounted on a surface plate.
Application in Nigeria: Marking lines parallel to the base of a workpiece for precision machining, checking the height of a component, or setting up tools for specific operations.
Chalk and Marking Pen: Description: Chalk (like tailor's chalk or industrial chalk) and permanent markers.
Function: Used for making temporary, visible marks on rougher metal surfaces, especially for larger layouts or where precision is not extremely critical.
Application in Nigeria: Marking large cut lines on rusted or uncleaned metal sheets, indicating sections for removal during demolition or repair, or for quick general layout on structural components like roof trusses. Cutting tools are used to remove material from a workpiece to achieve the desired shape and size. Different tools are suited for different materials and types of cuts.
Hacksaw: Description: A hand tool consisting of a frame that holds a thin, replaceable blade with fine teeth. Blades come in various teeth per inch (TPI) counts for different materials.
Function: Used for manually cutting metal bars, pipes, angles, and sheets. It's effective for straight cuts and some curved cuts on thinner materials.
Application in Nigeria: Cutting mild steel pipes for gate frames, trimming excess length from angle irons, or cutting small diameter rods for various fabrication needs in local workshops.
Cold Chisel: Description: A hand tool made of hardened steel with a sharpened cutting edge, typically used with a hammer. It comes in various shapes (flat, cape, round-nose, diamond point).
Function: Used for cutting or shaping cold metal, shearing off rivet heads, removing excess weld material, or cutting thin sheet metal by hand.
Application in Nigeria: Cutting off seized bolts, splitting nuts, removing rusted rivets from old vehicle bodies, or roughly shaping metal components where precision is not the main concern.
Files: Description: Hand tools with hardened steel surfaces covered in sharp teeth (cuts). They come in various shapes (flat, half-round, round, square, triangular) and degrees of coarseness (rough, bastard, second cut, smooth).
Function: Used for removing small amounts of material, smoothing rough edges, deburring, and shaping metal.
Application in Nigeria: Smoothing the edges of a freshly cut metal plate, deburring holes after drilling, shaping small components for intricate repairs, or preparing surfaces for welding.
Angle Grinder: Description: A power tool that uses a rotating abrasive disc for cutting, grinding, and polishing metal. It is highly versatile but requires strict safety precautions.
Function: Used for fast cutting of metal, grinding welds smooth, removing rust, and preparing metal surfaces. Different discs are used for cutting, grinding, or sanding.
Application in Nigeria: Rapidly cutting thick steel plates for structural fabrication, grinding down rough weld beads on gates and railings, shaping metal, or preparing rusted surfaces for painting in almost any metalworking shop. (Safety is paramount: eye protection, ear protection, gloves, proper handling). Plasma Cutter (Brief mention for advanced work): Description: A power tool that cuts through electrically conductive materials by means of an accelerated jet of hot plasma.
Function: For very fast and precise cutting of various metals, especially thicker plates, and for intricate shapes.
Application in Nigeria: Used in larger fabrication shops or industrial settings for high-volume cutting, creating complex metal designs for decorative gates, or cutting heavy-gauge steel for machinery parts. --- This section details the various measuring instruments, marking out tools, and cutting tools used in welding and fabrication, providing their descriptions, functions, and typical applications.
This section highlights how the knowledge of these tools is directly applied in various aspects of Nigerian life and economy. Fabrication of Domestic and Commercial Metalwork: Application: Artisans and welders across Nigeria use these tools daily to fabricate metal gates, window grilles, security doors, stair railings, and furniture for homes and businesses. For example, a welder in Onitsha uses a tape measure to get the overall dimensions of a gate, a scriber to mark cutting lines on square pipes, and an angle grinder to cut and smooth the steel sections before welding.
Integration: This knowledge empowers students to pursue careers in local fabrication shops, contribute to community infrastructure development, or even start their own small-scale metalworking businesses.
Automotive Repair and Panel Beating: Application: In mechanic villages across Nigeria, panel beaters and automotive technicians rely heavily on these tools. A Vernier caliper might be used to measure specific engine parts, a centre punch to mark drill points on a rusted chassis for repair, or chisels to remove old rivets from a vehicle body. Files are indispensable for smoothing out repaired panels before painting.
Integration: Understanding these tools is fundamental for aspiring automotive technicians, enabling them to perform accurate repairs, maintain vehicles, and contribute to the transport sector.
Agriculture and Rural Technology: Application: Farmers and rural blacksmiths in Nigeria use these tools for fabricating and repairing farm implements such as hoes, ploughs, irrigation pipes, and animal enclosures. A steel rule might measure pipe lengths for an irrigation system, chalk might mark cutting lines on worn-out farm equipment for repair, and a hacksaw or grinder might cut metal for new parts.
Integration: This knowledge aids in improving agricultural productivity through better maintenance of tools and machinery, fostering local innovation in tool design, and supporting rural livelihoods. ---