GEAR – A wheel with teeth that engage or mesh with teeth of another wheel.

GEAR BOX – A unit which has a series of gears and shafts to vary the speed of the gearbox output shaft compared to the engine speed. This in turn increases the torque and thereby improves acceleration of the vehicle.

GEAR CLASH – A condition in which the gears grind during shifting.

GEAR RATIO – The ratio of the number of teeth on two gears to mesh with each other.

GENERATOR – is the device which converts mechanical energy from the automobile engine into electrical energy. When the generator is sufficiently turned by the engine, it furnishes electrical energy for all the vehicles circuits and replenishes the battery to keep it fully charged.

GRAVITY BLEEDING – A process used to remove air from the brake system using the natural height of the fluid in the master cylinder above the wheel cylinder.

GRIP COEFFICIENT – is numerically equal to the ratio of the force causing uniform wheel slip to the normal road resistance.

GLOW PLUG – is an electrical heater, which is switched on for quick starting in cold weather. Its heating element protrudes directly into the combustion chamber in DI engines.

GOVERNOR – Mechanism connected to the control rack of the fuel injection pump and thus acts as an intermediate mechanism between the control rack and accelerator pedal.

GAS HOLES – Rounded cavities caused by generation or accumulation of gas or entrapped air in a casting, holes may be spherical, flattened or elongated.

GATE – The location where the molten metal enters the casting cavity.

GATED PATTERN – One or more patterns with gating systems attached.

GATING SYSTEM – Combination of channels, cavities and other elements of a casting mould which are intended ·to feed molten metal into a mould, fill in the latter, and feed up the casting with metal during solidification.

GRAVITY DIE CASTING – is one in which the fluid metal is poured by hand into the metal moulds and around metal cores. The only pressure applied is that exerted by the head of metal in the pouring gate.

GREEN SAND – Prepared moulding sand in the moist or as mixed condition.

GREEN SAND MOULD – Mould made and cast in damp sand.

GUIDE PIN – The pin used to locate the cope in the proper place on the drag.

GAMMA IRON – The face centered cubic form of pure iron, stable from 910-1230°C.

GANGUE – The worthless portion of an ore that is separated from the desired part before smelting is commenced.

GEL COAT – A thin coat of plastic resin covering fibreglass panels.

GILDING METAL – Alloy containing 80-90% copper, the reminder being zinc. Often used in wire form for jewellery and decorative applications.

GLACIER METAL – Tin base alloy used for lining bearings.

GLASS – Transparent substance produced by the fusion of sand and certain metallic salts, of which soda compounds are most common.

GLUE LAMINATED BEAM – A structural wood beam made by gluing thinner boards together until a desired dimension for beam thickness is reached. Glue laminated beam will support large loads and can span long distances with only end support.

GRAIN – Individual crystal in metals.

GRANITE – A rock composed of quartz, feldspar and mica from which dimensionally stable surface plates and angle plates are made.

GRANULAR PEARLITE – A structure formed from ordinary lamellar pearlite by long annealing at a temperature below but near to the critical point, causing the cementite to spherodize in a ferritic matrix.

GRAPHITE – Native carbon in hexagonal crystals, also foliated or granular massive, of black colour with metallic lusture, and soft.

GRAPHITE FIBRE – Strands of carbon in graphite form used in composite materials as the main load bearing constituent.

GRAPHITIZER – Any substance, such as silicon, titanium, aluminium etc. which promotes the formation of graphite in cast iron compositions.

GRAY CAST IRON – A cast iron that gives a gray fracture due to the presence of flake graphite. Often called GRAY IRON.

GRIT SIZE – Nominal size of abrasive particles in a grinding wheel corresponding to the number of openings per linear inch in a screen through which the particles can just pass. Sometimes called GRAIN SIZE.

GUN METAL – Bronze alloy containing 88-89% copper, 5-10% tin and 2-6% zinc, lead up to 20% may also be added, although the quantity seldom exceeds 5%.

GEAR OIL PUMP – An oil pump with gear type teeth to move oil.

GREASE – The term is applied to a mixture of mineral oil with fats that have been saponified with an alkali. To this mixture fillers may or may not be added.

GAS – A state of matter, neither solid nor liquid which has neither definite shape nor definite volume. Air is a mixture of several gases.

GASOLINE – A liquid blend of hydrocarbons, obtained from petroleum crude oil, used as the fuel for most automobile SI engines.

GRINDABILITY – A descriptive term of a characteristic of coal that is important to pulverized coal systems.

GAGING – Ratio of the net area of gas flow to the total free annular area in the blade ring.

GAS TURBINE – A rotary machine, which consists of a compressor, combustion chamber and a turbine. Air is compressed in the compressor, passed into the combustion chamber where fuel is burnt, products of combustion impinge over rings of turbine blades with high velocity and work is done.

GUIDE BLADES – Row of blades interposed between the blade rows comprising rotor passages, so as to reverse the direction of the fluid leaving the preceding moving blade row and make the general direction of the fluid entering all the moving blade rows to be similar.

GALVANIZING – Rust prevention treatment which consists of coating the metal (iron or steel) with a fairly thick film of zinc.

GASKET – A flat strip, usually of cork or other material, placed between two non-moving, machined surfaces to provide a tight seal between them and thereby prevent leakage.

GASKET CEMENT – A liquid adhesive material, or sealer applied on gaskets, in some applications, the liquid layer of gasket cement is used as the gasket itself.

GLAZE (cylinder) – The mirror like, very smooth finish that develops on engine cylinder walls during engine operation.

GAUGE – A tool or instrument for checking or measuring the sizes of metal parts to determine whether the dimensions are within the specified limits.

GAUGE BLOCKS – are used mostly for reference in setting gauges and for accurate measurement in tool, gauge, and die manufacture.

GIB – An angular or wedge like strip of metal placed between two machine parts, usually sliding bearings to ensure a proper fit and provide adjustment for wear.

GOGGLES – These are worn when tool grinding, to protect the eyes from the flying particles of grit.

GATE VALVE – A common type of manually operated valve in which a sliding gate is used to obstruct the flow of fluid.

GEAR – A general term applied to types of toothed wheels, valve motion, pump works, lifting tackle and ropes.

GEARING – A train of gears or an arrangement of gears for transmitting motion in a machinery.

GIB – An angular or wedge like strip of metal placed between two machine parts, usually sliding bearings, to ensure a proper fit and provide adjustment for wear.

GLAND – A device to prevent the leakage of gas or liquid past a joint.

GANG DRILLING MACHINE – A drill press in which two or more drilling spindles are mounted on a single table. This permits several drilling operations to be made by moving the workpiece from spindle to spindle in a planned sequence.

GAUGE SNUBBER – A device installed in the fuel line connected to the pressure gauge, used to dampen pressure surges and thus provide a steady reading. This helps protect the gauge.

GEAR TYPE PUMP – A pump which uses the space between the adjacent teeth of gears for moving the liquid.

GENERATOR – An electromagnetic device used to generate electricity.

GOVERNOR – A device for controlling the speed of a prime mover, which produces power.

GRINDING MACHINE – Machine designed for one or other or a combination of the following functions. Grinding excess material off parts previously machined by other methods; forming parts from blanks; parting off lengths of material from rods, bars, billets and so on.

GANTRY CRANE – Crane consisting of a bridge crane superimposed on two frames or legs operating on a rail track flush with the ground.

GENERAL MERCHANDISE WAREHOUSE – The most common type of public warehouse for storing manufactured or non-manufactured goods that require protection.

GONDALA – A car with low sides and no top.

GRAB – Device suspended from the crane hook which grasp and release the load (of given shape and size) at almost no time.

GRAVITY ROLLER CONVEYOR – A material handling installation in which the bed consists of rolls fitted to a frame. Suitable for handling of unit loads and containerized high volume materials.

GRAIN BOUNDARY – The outer perimeter of a single grain where it is in contact with adjacent grains.

GRAIN GROWTH OR RECRYSTALLIZATION – Metal grains begin to reform to larger and more regular size and shape at certain temperatures, depending to some extent on the amount of prior cold working.

GRAIN REFINER – A material added to a molten metal to attain finer grains in the final structure.

GRAIN SIZE – For metals, a measure of the area or volume of grains in polycrystalline material, usually expressed as an average when the individual sizes are fairly uniform. Reported in terms of number of grains per unit area or volume, average diameter, or as a grain size number derived from area measurements.

GRANULAR PEARLITE – A structure formed from ordinary lamellar pearlite by long annealing at a temperature below but near to the critical point, causing the cementite to spherodize in a ferrite matrix.

GROWTH – With reference to cast iron, permanent increase in volume that results from continued or repeated cyclic heating and cooling at elevated temperatures.

GALVANIZING – The application of a layer of zinc to the surface of iron and steel for protection from corrosion.

GAS WELDING – Method of fusion welding in which a flame produced by the combustion of gases is employed to melt the metal.

GEAR CUTTING – Production of gear wheels by the various forms of shaping tools or rotary cutters.

GEAR HOBBING – Method of generating gear teeth by the use of a rotating worm shaped cutter.

GEAR PLANING – Production of gear wheels by the use of cutters having a sliding instead of a rotary action.

GENERATING GEAR TEETH – Production of correctly formed gear teeth automatically, without the use of cutter of intricate shape.

GRAVITY DIE CASTING – Production of casting by pouring molten metal into metallic moulds under the force of gravity only.

GRINDING – Finishing operation designed to give to parts already machined the necessary precision of form and accuracy of dimensions by the removal of excess material due to the cutting action of grains of abrasive in a wheel or disc.

GEAR CLEARANCE – The radial distance from the top of the tooth to the bottom of the tooth space in a mating gear unit.

GEAR TRAIN – Unit composed of two or more gears in mesh for the purpose of transmitting motion from one shaft to another.

GOVERNOR – Device that controls the mean speed of an engine over a period of time, as distinct from the flywheel, which limits the fluctuation of speed during one cycle but is not able to prevent a change in mean speed from cycle to cycle.

GOVERNOR EFFORT – Mean force exerted at a sleeve due to a 1% change in speed of governor.

GOVERNOR POWER – Work done at the sleeve for a 1% change in speed, equal to the governor effort times the sleeve displacement.

GYROSCOPIC ACCELERATION – The rate of change of angular velocity of precision of a rotating disc.

GAS VOLUME CONTROL – Used to regulate the amount of gas needed to produce certain desired temperatures and conditions in domestic absorption automatic control refrigerators.

GROUNDING – Protection against static charges which sometimes build upon operating equipment.

GALLOWAY TUBES – Transverse tubes placed in a flue tube and attached to the openings in the side of the flue to increase the heating surface.

GAUGE COCK – A device for determining the water level in the boiler.

GIRDER STAY – A cast steel or built up girder with its ends resting on the side or end sheets of the fire box or combustion chamber, and supporting the flat crown sheet or top sheet of the combustion chamber by means of bolts.

GOOSE NECK – A short length of pipe having one complete turn to which the steam gauge is attached.

GRATE SURFACE – The area of the grate upon which fire rests in a coal or wood fired boiler.

GROOVING – Surface cracking of boiler plates. Expansion and contraction of parts too rigidly connected cause grooving.

GROSS FEED WATER – The net feed water plus the quantity of water provided for that blown out.

GUSSET STAY – Pieces of plate iron secured to the boiler front or back near the top or bottom by means of angle irons.

GLAND – Device provided to minimise the leakage of steam, or in the case of the low pressure end of the turbine the leakage of air through the clearance space which separates the rotor from the casing.

GAUGE PRESSURE – Pressure above or below atmospheric pressure.

GAY LUSSAC LAW – The volume of a gas will vary directly as the absolute temperature, if the pressure remains constant.

GASES – are substances in which the molecules move freely and exist in an unbound state. Gases can be compressed easily because of the large empty space available between the molecules.

GAS CHARGED SHOCK ABSORBER – A shock absorber using a pressurized gas such as nitrogen to help prevent changes in damping as shock absorber heats up.

GUSSET – A reinforcing plate or boxed section used to prevent flexing of frame or swing arm.