COREN Craftsman key terms

Established points, lines or faces from which dimensions and tolerances are measured during marking out, machining or inspection. Correct choice of datum prevents accumulated error when a workpiece passes through several operations.

The workshop process of transferring dimensions from a drawing onto a workpiece using scribers, dividers, surface plates and punches, producing layout lines that guide cutting and machining.

A hardened, pointed hand tool struck with a hammer to make a small conical indentation that locates a drill bit and stops it wandering on a metal surface.

The permitted maximum and minimum sizes of mating parts and the resulting clearance, interference or transition assembly, selected so parts function correctly without unnecessary precision cost.

The total permissible variation between the upper and lower size limits of a dimension; it defines how much inaccuracy a manufactured feature may have and still be accepted.

The intentional difference between the sizes of two mating parts before assembly, deliberately designed as clearance or interference; it differs from tolerance, which is unintentional manufacturing variation.

The fine-scale irregularities left by a cutting or forming process, expressed as an average deviation value and specified on drawings to control friction, wear and fatigue performance.

The arrangement of point angle, helix angle, lip clearance and chisel edge on a twist drill, which together determine cutting efficiency, chip flow and the tendency of the drill to wander.

Cutting speed is the rate at which the cutting edge passes through the material, usually in metres per minute; feed is the advance per revolution or per stroke. Both govern tool life and finish.

Progressive loss of cutting-edge material through abrasion, adhesion, diffusion or chipping, monitored by flank wear and cratering; excessive wear degrades dimensional accuracy and surface finish.

A drawing method in which parallel projectors meet the plane of projection at right angles, giving true shapes and sizes of features on views arranged according to first- or third-angle convention.

Two standard arrangements of orthographic views: in first angle the object sits between observer and plane, so the view appears on the far side; in third angle the plane sits between observer and object.

A pictorial drawing in which the three principal axes are inclined equally to the picture plane, so all three are drawn at 120 degrees and dimensions along them share a single scale.

A view produced by imagining a cutting plane passed through an object and removing the nearer part, revealing internal features; cut material is shown with hatching at a consistent angle.

Agreed rules for line types, dimensioning, hatching, symbols and lettering that make drawings unambiguous and internationally readable without accompanying explanatory text.

A symbolic system for specifying form, orientation, location and runout tolerances relative to datums, communicating functional requirements more precisely than simple linear dimensioning.

A drawing notation comprising a reference line, arrow, and supplementary symbols that specify weld type, size, length, spacing and any contouring or finishing requirements.

A structured list accompanying or embedded in a drawing that itemises components, part numbers, descriptions, quantities and material specifications needed to manufacture or assemble the product.

The broad classification of metals by iron content: ferrous alloys such as steel and cast iron are magnetic and iron-based, while non-ferrous metals such as aluminium, copper and zinc contain no significant iron.

An iron-carbon alloy containing small percentages of carbon and manganese, classified as low, medium or high carbon according to carbon content, which controls hardness, strength and weldability.

Controlled heating and cooling cycles such as annealing, normalising, hardening and tempering that alter microstructure and therefore hardness, toughness and machinability without changing chemical composition.

A surface treatment that enriches the outer layer of low-carbon steel with carbon or nitrogen, then hardens it, producing a wear-resistant skin over a tough, shock-resistant core.

An iron-carbon alloy with carbon content typically above two percent, valued for casting fluidity, damping capacity and compressive strength, though generally brittle in tension.

A document supplied with a batch of material recording its chemical composition and mechanical properties from mill testing, used to verify conformity with the specification before fabrication.

Precision measuring instruments: the micrometer uses a calibrated screw to measure small thicknesses to hundredths of a millimetre, while the vernier calliper measures internal, external and depth dimensions with a sliding scale.

Inspection methods such as dye penetrant, magnetic particle, ultrasonic and radiographic testing that reveal surface or internal defects without damaging the component, usually applied to welds and castings.

Physical barriers and sensing devices fitted to machinery that prevent access to dangerous moving parts and stop or disable the machine when a guard is opened or defeated.

A procedure for isolating energy sources, applying personal locks and warning tags, and verifying zero energy before maintenance, so equipment cannot be restarted while someone is working on it.

A formal written authorisation controlling high-risk tasks such as hot work, confined-space entry or work on live systems, recording hazards, precautions, isolations and the responsible signatories.

Clothing and equipment worn to reduce exposure to workplace hazards, such as helmets, eye protection, gloves, hearing protection and respiratory devices; it is the last line of defence.

The systematic process of recognising sources of potential harm in a task or workplace, forming the first step of risk assessment before controls are chosen.

The structured evaluation of identified hazards to estimate likelihood and severity of harm, rank risks and select proportionate controls, with the assessment reviewed and recorded.

The order of preference for managing risk: eliminate the hazard, substitute it, use engineering controls, apply administrative controls, and finally rely on personal protective equipment.

The statutory process by which the Council for the Regulation of Engineering in Nigeria registers qualified engineers, technologists and technicians, authorising them to practise and use protected titles.

The published ethical standards binding registered practitioners, covering competence, honesty, confidentiality, avoidance of conflicts of interest and duties to the public, employers and the profession.

Failure to exercise the reasonable skill and care expected of a competent practitioner in the same field, resulting in loss or harm to a client or third party.

Insurance covering a practitioner or firm against claims of financial loss arising from errors, omissions or negligent professional advice and design work.

A situation where a practitioner's personal, financial or other interest could improperly influence professional judgement; it must be disclosed and managed or the engagement declined.