JCE Metalwork key terms

The ability of a metal to be stretched or drawn into thin wire without breaking. Copper and mild steel are ductile, which is why they can be bent or pulled into shape rather than snapping.

The ability of a metal to be hammered or rolled into thin flat sheets without cracking. Aluminium and copper are highly malleable, so they suit panel beating and press forming.

The maximum pulling force a material withstands before it fractures, usually given in newtons per square millimetre. High-tensile bolts use steel with a high value so joints do not fail under load.

A material's resistance to scratching, indentation or wear. Hardened tool steel keeps a sharp cutting edge, while soft metals like aluminium mark easily and are unsuitable for chisel tips.

A heat treatment that softens a metal by heating it and then cooling it slowly. It relieves work hardening so the metal can be bent or shaped further without cracking.

The increase in hardness and brittleness a metal gains when it is bent, hammered or rolled repeatedly. Metal that has work hardened must be annealed before further forming or it may crack.

A heat treatment applied after hardening that reduces brittleness while keeping useful hardness. Tool steel is tempered to a straw or blue colour to suit cutting or striking duties.

Any metal whose main constituent is iron, such as mild steel, cast iron and high-carbon steel. Ferrous metals are magnetic and will rust unless protected by paint, oil or plating.

A metal that contains little or no iron, for example aluminium, copper, brass and zinc. These resist rust, are generally lighter, and are chosen for electrical and decorative work.

A metal made by melting two or more elements together to gain better properties. Brass is copper plus zinc, and stainless steel adds chromium to iron to resist corrosion.

Coating steel with a thin layer of zinc, usually by hot dipping, to prevent rust. The zinc corrodes in preference to the steel, so the protection continues even where the coating is scratched.

A bench-mounted clamping device with two jaws, used to hold work securely while it is cut, filed or drilled. Soft jaw covers protect finished surfaces from being marked by the serrated jaws.

A hardened steel tool with many cut teeth used to smooth, shape or remove small amounts of metal. The grade, cut and shape of the file are chosen to suit the job.

A filing technique where the file is held across the work and pushed along its length to produce a smooth, flat finish. It is used to remove file marks before polishing or fitting.

A hand saw with a fine-toothed replaceable blade held under tension in a frame, used to cut metal bar and tube. Blades are fitted with teeth pointing forward and cut on the push stroke.

A hardened steel punch with a sharp point, struck with a hammer to make a small dimple that locates a drill bit. It is used after marking out so the drill does not wander on the surface.

A sharp-pointed steel tool used to scratch fine layout lines on metal. It is used with a steel rule and square, and should never be used to mark a cut line on a finished face.

A floor-standing drilling machine with a vertical column and a table that can be raised or lowered. The work is clamped to the table and the spindle is fed downwards by a hand lever.

A machine that rotates the workpiece against a stationary cutting tool to produce cylindrical or faced surfaces. It is used for turning shafts, boring holes and cutting screw threads.

The rate at which the cutting edge of a tool passes through the material, usually measured in metres per minute. It depends on the material and tool type, and is reduced for harder metals.

The distance a cutting tool advances into the work per revolution or per stroke. Too high a feed overloads the tool and machine, while too low a feed rubs and dulls the edge.

A permanent fastening method in which a soft metal pin is passed through aligned holes and its tail is spread to clamp the parts. It suits sheet metal where a welded or bolted joint is unsuitable.

A joining process where a filler metal with a lower melting point than the parts is melted into the joint gap. Unlike welding, the parent metal does not melt, so distortion is limited.

A permanent joining process that melts the edges of the parts, often with a filler rod, to form one continuous piece. It produces a strong joint but can distort thin sheet and needs eye protection.

A releasable fastening made with a threaded bolt, nut and often a washer through drilled holes. It allows parts to be dismantled for maintenance and is common in machine assembly.

A hardened threaded tool used to cut an internal screw thread in a drilled hole. The hole must first be drilled to the correct tapping size, slightly smaller than the thread diameter.

A hardened tool with a threaded hole used to cut an external screw thread on a rod or bolt blank. The rod is held in a vice and the die is turned slowly with cutting lubricant.

A measuring instrument with a sliding jaw and a vernier scale that reads to 0.02 mm or similar. It measures outside, inside and depth dimensions, making it a versatile workshop gauge.

A precision measuring instrument using a calibrated screw to measure small thicknesses and diameters, typically to 0.01 mm. It is read by combining the barrel and thimble scales.

The total amount by which a dimension may legally vary while still being acceptable. A dimension of 20 mm with a tolerance of plus or minus 0.1 mm may measure between 19.9 and 20.1 mm.

A reference point, line or surface from which measurements and positions are taken during marking out or machining. Using a consistent datum prevents errors accumulating across a component.

A drawing method showing a three-dimensional object as separate front, plan and side views, arranged in a standard layout. Each view is a true shape seen straight on, so dimensions can be read directly.

A three-dimensional pictorial drawing in which the three axes are drawn at 30 degrees to the horizontal, giving equal scale along each. It communicates shape clearly but does not show true sizes or angles.

The ratio between a drawing and the real object, such as 1:2 for a half-size drawing. The scale must be stated on the drawing so dimensions can be checked or measured by the maker.

A short written statement of the problem, the intended user and the main requirements a product must meet. It guides research and helps evaluate whether the finished outcome is successful.

A detailed list of measurable requirements such as size, material, finish, cost and safety limits that a product must satisfy. It turns the broad design brief into criteria that can be tested.

The process of judging a finished product against the specification to decide how well it meets the user's needs. It identifies strengths and improvements that would feed into a future design.

Items worn to protect the worker from hazards, such as safety glasses, gloves, ear defenders and an apron. It is the last line of defence and does not replace guards or safe working methods.

A careful examination of a task to identify hazards, judge how likely and severe any harm is, and decide on controls. The findings are recorded and controls are put in place before work begins.

A physical barrier fitted around rotating or cutting parts to prevent hands or clothing reaching danger points. Guards must be in position before a machine is started and must not be removed while running.

A material sourced and processed so that environmental impact is limited, for example recycled aluminium or timber from managed forests. Choosing it reduces waste and energy use over a product's life.

Collecting and reprocessing waste material into new usable stock, such as melting scrap aluminium into new billets. It saves raw material and energy, and should be considered when selecting materials.

A study of a product's environmental impact from raw material extraction through manufacture, use and disposal. It helps designers compare options and reduce harm at the most damaging stage.