NSSCO Metalwork and Welding 6188 key terms

Equipment worn or held by a worker to reduce exposure to hazards, such as goggles, gloves, ear defenders, respirators, safety boots and welding helmets. It supplements, but does not replace, engineering controls and safe working procedures.

A careful process of identifying hazards in a task, judging how likely and how severe harm could be, and deciding controls to remove or reduce that risk before work starts.

The three conditions needed for ordinary combustion: fuel, oxygen and enough heat to start and sustain burning. Removing any one side prevents or stops a fire.

A ventilation system that captures welding smoke, solder flux fumes, dust or solvent vapour near its source and carries it away from the worker's breathing zone.

A document supplied with a hazardous chemical that summarises hazards, safe handling, storage, first aid, spill response and disposal. Workers should read it before using an unfamiliar product.

A metal whose main constituent is iron, often with carbon and alloying elements. Mild steel, cast iron and many tool steels are ferrous; most are magnetic and can rust.

A metal that contains no significant iron content. Aluminium, copper, brass, lead and zinc are examples; they are generally non-magnetic and resist rust, though they may corrode.

The ability of a metal to be stretched or drawn into thin wire or long shapes without breaking. Ductile metals deform permanently under tension, which helps in forming and bending.

A metal's resistance to scratching, indentation or wear. Hardness often increases with carbon content or heat treatment, but very hard metals may become brittle.

The ability of a metal to absorb energy and deform without fracturing, especially under impact. Toughness differs from hardness and is important for tools and structures subjected to shock.

A reference point, line or surface from which measurements and dimensions are taken. Using a clear datum reduces accumulated error when marking out or machining a part.

A measuring tool with a fixed main scale and a sliding vernier scale. It measures outside, inside and depth dimensions, commonly to 0.02 mm or 0.001 inch.

A thin blue coating applied to a metal surface so scribed lines show clearly. It helps the worker mark out accurately and see fine layout lines against the shiny metal.

A sharp-pointed hand tool used to scratch fine layout lines on metal. It should be used with a straightedge or template and handled carefully because its point is sharp.

A pointed punch struck with a hammer to make a small indentation. The dent guides a twist drill so it starts without wandering, especially on smooth or curved surfaces.

A hand saw with a fine-toothed replaceable blade held under tension in a frame. It cuts metal bar, tube and sheet; blade pitch and cutting pressure must suit the material thickness.

A rotating cutting tool with helical flutes and a pointed tip, used to produce round holes in metal. Correct speed, feed and coolant improve hole quality and tool life.

A cutting tool that enlarges the top of a hole into a conical seat. It lets a countersunk screw or rivet sit flush with, or slightly below, the workpiece surface.

Hand shears with short, hardened cutting blades for cutting thin sheet metal. Straight, left-cutting and right-cutting patterns allow curves and notches to be cut accurately.

A folded edge on sheet metal that stiffens the sheet and removes a sharp raw edge. The fold is usually made over a straight edge or in a folding machine.

A heat treatment that softens metal by heating it to a suitable temperature, holding it, then cooling slowly. It relieves internal stress and restores workability after cold forming or welding.

A heat treatment that heats steel above its critical range, holds it, then cools it in still air. It refines grain structure and produces a more uniform, stress-reduced condition.

Rapid cooling of heated metal by plunging it into water, oil or polymer. In hardenable steels it produces a hard but often brittle structure that usually needs tempering.

Shaping heated metal by controlled hammering, pressing or rolling. Forging refines the grain flow, improves strength and allows large changes in shape without cutting away material.

A permanent fastener with a shank and a formed head. It is inserted through aligned holes and the plain end is deformed to clamp parts together; common in sheet metalwork.

A joining process that melts a low-melting filler metal, usually tin-lead or lead-free alloy, which wets and bonds the parts without melting them. Flux cleans the surfaces.

A joining process using a filler metal that melts above about 450 degrees Celsius but below the melting point of the parent metals. Capillary action draws filler into the joint.

Manual metal arc welding uses a consumable coated electrode and an electric arc to melt parent metal and electrode. The coating shields the weld and forms slag.

Metal inert gas welding feeds a continuous consumable wire electrode through a torch while shielding gas protects the molten weld pool. It suits thin sheet and production work.

The first weld run deposited at the bottom of a joint preparation. It must fuse both root faces and control penetration, because later passes build on this foundation.

Unwanted changes in shape or size caused by uneven heating, cooling or shrinkage during welding. It can be controlled by balanced sequences, clamping, tacking and suitable joint design.

A drawing method showing an object from different directions on separate views, usually front, top and side, arranged to a standard. Dimensions define the part without perspective.

A pictorial drawing with three axes spaced 120 degrees apart, showing length, width and height without perspective. It gives a clear 3D impression but is not usually dimensioned for manufacture.

A table listing each piece required for a job, with material, size, quantity and any notes. It helps plan material use, avoid waste and check parts before assembly.

The permitted variation between a stated nominal dimension and the actual acceptable size. Tolerances tell the maker how accurately a feature must be produced for fit and function.