ITI/NCVT Tool & Die Maker (AITT Theory) key terms

A written authorisation that confirms hazards have been identified, isolation and precautions are in place, and the specified work may start. It is signed before maintenance or hot work begins and closed when the job ends.

A procedure in which energy sources are switched off, physically locked and tagged so machinery cannot be restarted while someone is working on or inside it. Each worker applies a personal lock.

A workplace method with five steps: sort, set in order, shine, standardise and sustain. It removes unneeded items, gives every tool a marked place and keeps benches and machines clean and inspection-ready.

A supplier document, typically in sixteen sections, describing a chemical's hazards, composition, first-aid, firefighting, spill and disposal measures, and required PPE. It must be available where the substance is stored or used.

A heat treatment that softens steel by heating it above its critical temperature, holding until the structure becomes austenite, then cooling very slowly, usually in a furnace. It relieves internal stress and improves machinability.

Rapid cooling of austenitised steel in water, oil, polymer or air to form hard martensite. Cooling speed must suit the steel grade: too slow gives a soft structure, too fast risks cracks and distortion.

Reheating hardened steel to a temperature below its critical range, holding, then cooling to reduce brittleness and relieve internal stress. The chosen temperature sets the trade-off between toughness and hardness.

Any process that hardens only the outer skin of low-carbon steel while the core stays tough. Carburising, nitriding and induction hardening are common; the case depth is specified on the drawing.

A tool steel alloyed with tungsten, molybdenum, vanadium and chromium that keeps its hardness at red heat. It is the standard material for drills, taps, milling cutters and single-point lathe tools.

A measuring instrument with a main scale and a sliding vernier scale, giving least counts of 0.02 mm or 0.05 mm. Inside, outside and depth jaws let one tool measure several features.

A precision instrument using a calibrated screw and thimble to measure small dimensions, commonly to 0.01 mm. The spindle and anvil contact the work, and a ratchet stops over-tightening.

A flat, rigid cast iron or granite plate used as a reference plane for marking out, setting and inspection. Its surface is scraped or lapped flat and must be kept clean and free from impacts.

The system of upper and lower permissible sizes for mating parts, plus the resulting clearance or interference. Hole-basis fits with letter and number codes tell the shop how tight a joint should be.

Cutting tools for making threads by hand. A tap cuts an internal thread in a drilled hole; a die cuts an external thread on a rod. Tapping needs the correct drill size and plenty of lubrication.

The movable assembly at the far end of a lathe bed. It supports long work on a centre, holds drills and reamers in its quill, and can be offset for turning long shallow tapers.

The rate at which the cutting edge travels past the work surface, expressed in metres per minute. It depends on work and tool material and sets spindle speed through the work diameter.

The included angle of the conical tip of a twist drill, normally 118 degrees for general steel work. Too large an angle makes the drill rub; too small makes the point fragile and slow.

The strength of the bond holding abrasive grains in a grinding wheel, lettered from soft to hard. Soft grades release blunt grains in hard work; hard grades suit soft materials and form grinding.

Producing a conical surface on a lathe, usually by swivelling the compound slide, offsetting the tailstock, or using a taper turning attachment. Included angle and taper ratio come from the drawing.

A work-holding device that also guides the cutting tool, typically through hardened bushes, so holes are drilled in the same place every cycle. It normally travels with the workpiece.

A device that holds and locates a workpiece securely during machining but does not guide the tool. It is clamped to the machine table and is justified when parts are made in quantity.

A rule for full location: three points stop movement along one axis and two rotations, two points stop a second rotation, one point stops the last. Extra points cause rocking and error.

The punch holder, die shoe and guide pillar-and-bush assembly that aligns a press tool. It carries the punch and die inserts, keeps their clearance constant and mounts in the press ram and bed.

A plate that holds the workpiece flat on the die while the punch withdraws, or pushes the part off the punch. Spring- or urethane-loaded types prevent the part lifting with the punch.

A press operation that cuts a closed contour from sheet metal where the cut-out piece is the wanted product. The surrounding sheet becomes scrap, so nesting directly affects material cost.

A press operation that cuts a hole in sheet metal while the sheet itself remains the product and the slug is scrap. Piercing uses the same cutting action as blanking but a different intent.

A press tool with several stations in which the strip advances one pitch per stroke, so each station performs a different operation. It suits high-volume parts but needs an accurate strip feed.

The force a press can deliver at the ram, and the force a tool needs to shear, bend or draw the material. Required tonnage rises with material thickness, shear strength and cut length.

The part-program words that tell a CNC machine what motion to make, for example G01 for linear feed and G02 for clockwise circular interpolation. Modal codes stay active until cancelled.

Programmable machine functions in a CNC program that are not axis movement, such as spindle on, coolant on, tool change and program stop. Each M-code number is defined by the particular control.

Software that converts CAM toolpath output into the G- and M-code dialect of a particular machine control, adding feeds, speeds, tool changes and cycle formats that the control accepts.

A single G-code block that performs a fixed sequence of machining moves, such as drilling, boring or tapping with automatic retract. It shortens programs and is cancelled by G80.

A drawing convention in which the object sits between the observer and the plane, so the view seen from the front is placed below the front view and the left view goes on the right.

A drawing view in which material is imagined cut away to show internal shapes. Cut surfaces are hatched; ribs and shafts cut lengthwise are left unhatched by convention.

A symbolic drawing language that controls form, orientation, location and runout of features using tolerance frames, datums and modifiers, allowing larger tolerances without losing function.

A precision bar with two rollers a known distance apart, used with slip gauges to set or measure angles. The angle comes from the sine of height difference over roller distance.

The length of the neutral axis in a bend, calculated from bend radius, bend angle and material thickness, then added to flat lengths when developing a bent sheet metal part.