BOYLE’S LAW – At constant temperature, the absolute pressure of a gas varies inversely as its volume.

BACK LOCKING – The steering gear is so constructed that it is easy to turn the vehicle by steering wheel, but it is difficult to turn the steering wheel by turning the front wheels. This back locking prevents the bumps and shocks experienced by the wheel on the road surface from being transmitted to the steering wheel.

BACKING PLATE – A mounting plate that holds the brake shoes, cam lever, pivot pins and springs inside the brake drum.

BALL JOINT – Flexible joint utilizing ball and socket type of construction, used in steering linkage set ups, steering knuckle pivot supports etc.

BALL JOINT ROCKER ARMS – Rocker arms that instead of being mounted on shaft, are mounted upon ball shaped devices on end of stud.

BALL JOINT STEERING KNUCKLE – Steering knuckle that pivots on ball joints instead on king pin.

BALL JOINT SUSPENSION – A type of front suspension, which does not use a steering knuckle. Instead, the wheel spindle is attached directly to the upper and lower suspension arms through ball joints. Allows movement up and down as well as rotation.

BALL STUD – Stud with a ball on end, commonly used in steering linkage to connect pitman arm to linkage, or to connect tie rods.

BALL AND TRUNNION JOINT – A type of universal joint which combines the universal joint and slip joint in one assembly.

BEAD (tyre) – Steel wire reinforced portion around a tyre opening that engages the wheel rim.

BELL HOUSING (clutch housing) – Metal (cast iron or aluminium) cover that surrounds flywheel and clutch, or torque converter assembly.

BELL MOUTH – The taper of a brake drum.

BELTED TYRE – A tyre that is reinforced with a build up of cord under the tread area.

BENCH BLEEDING – Process of removing air from the master cylinder pressure area before installing it in the vehicle.

BENDIX TYPE STARTER – A self engaging starter drive gear. Gear moves into engagement when starter armature shaft starts spinning and automatically disengages when starter stops and engine speed increases.

BIAS BELTED TYRE – A tyre in which plies are laid on the bias, criss crossing each other, with a circumferential belt on top of them. The rubber tread is vulcanized on top of the belt and plies.

BINDERS – Compounds that hold the friction materials together in brake linings.

BLEEDING – Removing air, pressure, fluid etc. from a closed system as in the brake system or air conditioning system.

BLEEDING (brakes) – Removal of air from hydraulic system. Bleeder screws are loosened at each wheel cylinder (one at a time) and brake fluid is forced from master cylinder through lines until all air is expelled.

BLEEDING (steering) – A process by which air is removed from a hydraulic system (power steering) by bleeding off part of the fluid or operating the system to work without the air.

BODY – The assembly of sheet metal sections together with windows, doors, seats and other parts, that provide an enclosure for the passengers, engine and so on.

BODY PANELS – Sheets or panels of steel which are fastened together by welding to form the vehicle body.

BODY ROLL – The vehicle body leaning sideways as the vehicle turns.

BOGIE – A small truck, of short wheel base running on rails, commonly used for the conveyance of coal, gold or other ores, concrete etc.

BONDED BRAKE LINING – Brake lining that is attached to the brake shoe by adhesive.

BONNET – British term for car hood.

BOOSTER – Device incorporated in a car system (such as brake and steering), to increase pressure output or decrease amount of effort required to operate or both.

BORG WARNER OVER DRIVE – A method of reducing engine rpm in relation to road speed. The unit is attached at the rear of the gear box and operates through epicyclic gears.

BRAKE – An energy conversion device that converts the energy of motion into heat energy and thereby slows down or stops a moving vehicle.

BRAKE (disc type) – Braking system which uses steel disc with calliper type lining application. When brakes are applied, section of lining on the calliper piston on each side of the spinning disc is forced against the disc thus imparting braking force. This type of brake is very resistance to brake fade. Also called disc brake system.

BRAKE ANCHOR – Steel stud upon which one end of brake shoes is either attached to or rests against. Anchor is firmly affixed to backing plate.

BRAKE ANTIROLL DEVICE – Unit installed in brake system to hold brake line pressure when car is stopped on upgrade, and brake pedal is released. Antiroll device will keep brakes applied until either clutch is released or, as in some models, accelerator is depressed.

BRAKE BACKING PLATE – Rigid steel plate upon which brake shoes are attached. Braking force applied to shoes is absorbed by backing plate.

BRAKE BAND – Band faced with brake lining, that encircles a brake drum. Used on several parking brake installations.

BRAKE BIAS – The stopping effort of the front wheels compared to that of the rear wheels.

BRAKE CALIPER – The hydraulic cylinder at the wheel used to apply the disc brake linings against the rotor.

BRAKE CLEARANCE – is the clearance provided between the lining and the drum or disc. Wear and tear of the lining increases this clearance and hence to be adjusted periodically.

BRAKE DRUM – Metal drum mounted to the vehicle wheel which forms  the outer shell of the brake. Brake shoes when moved out or moved apart press against the rotating drum to slow or stop drum and wheel rotation.

BRAKE EFFECTIVENESS – is how effectively the brakes perform their function. This depends on the area of the brake lining, amount of pressure applied to the brake shoes, radius of the brake drum, vehicle wheel radius, coefficient of friction of braking surfaces and coefficient of friction between the tyre and the road surface.

BRAKE FADE – A reduction or fading out of braking effectiveness due to loss of friction between brake shoes and drum. This is caused by overheating (heat build up) from excessively long and hard brake application for instance, when coming down a long hill or mountain.

BRAKE FEEL – The reaction of the brake pedal against the drivers foot, that tells him how heavily he is applying the brakes.

BRAKE FLUID – A special non -mineral oil fluid used in hydraulic braking system. Never use anything else in place of regular fluid.

BRAKE FLUSHING – Cleaning brake system by flushing with alcohol or brake fluid. Done to remove water, dirt or any other contaminant. Flushing fluid is placed in master cylinder and forced through lines and wheel cylinders where it exits at cylinder bleed screws.

BRAKE LINE – Special hydraulic tube made of steel, plastic or reinforced rubber suitably designed to withstand extreme pressure without deforming.

BRAKE LINING – A special high friction material made of asbestos and other materials bonded to brake shoes and brake pad plates. Brake lining produces friction and heat when it is forced against the brake drum or disc.

BRAKE PULL – A condition in which the vehicle turns each time the brakes are applied.

BRAKE ROTOR – The brake friction surface that rotates at wheel speed designed for contact with the brake pads on disc brake assemblies.

BRAKE SELF ADJUSTERS – A cable operated device used to adjust brake shoes automatically.

BRAKE SHOES (disc brakes) – Flat metal pieces lined with brake lining which are forced against the rotor face. Also called brake pads.

BRAKE SHOES (drum brakes) – Arc shaped metal pieces lined with heat resistant fibre. When forced against the brake drum, stops wheel rotation.

BRAKE SHOE HEEL – End of brake shoe adjacent to anchor bolt or pin.

BRAKE SHOE TOE – Free end of brake shoe, not attached to or resting against an anchor pin.

BRAKING SYSTEM EFFICIENCY – is measured in terms of the rate at which brake will bring the vehicle to a stationary position from a given speed. It is expressed as the ratio of the vehicle deceleration rate to the acceleration due to gravity.

BREAKE (tyre) – Rubber or fabric (or both) strip placed under the tread to provide additional protection for main tyre carcass.

BULK HEAD – The structural part of the vehicle connecting the front of the floor assembly to the roof structure.

BUMPER – which is attached to the vehicle frame takes the shock of impact or collision and transfer the same to the frame. By this means, damage to engine parts, radiator, lamps etc. is avoided.

BUMP STEER – The steering effect caused by the suspension moving through its travel.

BIFUEL ENGINE – has two injectors to inject two fuels. In this a small amount of a suitable auxiliary fuel is injected into the cylinder either during the intake stroke or early in the compression stroke. Slightly latter in the stroke, the primary fuel is injected.

BLUE SMOKE – The smoke that results from the burning of lubricating oil that reaches the combustion chamber.

BOSCH METERING SYSTEM – A fuel metering system in a diesel engine, with a helical groove in the plunger which covers and uncovers ports in the pump barrel and thereby varies the effective stroke of the fuel pump.

BACK DRAFT – Taper or draft which prevents removal of pattern from the mould.

BACKING SAND – Sand between the facing sand and the flask.

BAKED CORE – The core which has been subjected to heating or baking until it is thoroughly dry, as opposed to green sand core which is used in the moist state.

BASIN – A cavity on top of the cope into which molten metal is poured before it enters the sprue.

BEDDED IN MOULD – is the mould, the bottom half of which is made in the sand in the floor of the foundry. It may be covered with a cope, or cast open, according to the type of work.

BINDER – Material used to hold the grains of sand together in moulds or cores. May be cereal, oil, clay, resin, pitch etc.

BINDER, PLASTIC (resin) – Synthetic resin material used to hold grains of sand together in moulds or cores, may be phenol formaldehyde or urea formaldehyde thermosetting types.

BLACKING – Carbonaceous material for coating mould or core surfaces.

BLACK LEAD – Graphite for facing moulds and cores.

BLAST CLEANING – Removal of sand or oxide scale from castings by the impinging action of sand, metal shot or grit projected under air, water or centrifugal pressure.

BLEED – Molten metal oozing out of a casting stripped or removed from the mould before solidification.

BLENDED SAND – Mixture of sands of different grain sizes, clay content etc. to produce one, possessing characteristics more suitable for foundry use.

BLIND RISER – An internal riser which does not reach to the exterior of the mould.

BLISTER – Defect on the surface of a casting appearing as a shallow blow with a thin film of metal over it.

BLOWN CASTINGS – Castings in which bubbles, or blowholes, have been caused through gases, steam etc., generated when the mould is cast, finding their way into the metal.

BOND CLAY – Any clay suitable for use as a bonding material in the moulding sand.

BORIC ACID – Inhibitor used in facing sand for magnesium base and aluminium base alloys high in magnesium to prevent reaction with moisture in the sand.

BORON TRICHLORIDE – A product used for degasification of aluminium alloys.

BOSSES – Bosses are often located on a wall of a casting and should be so designed that a heavy section of metal leads to the riser.

BOT – Clay wedge used in a cupola to stop the hole through which the metal is run.

BUCKLE – Defect in a casting surface appearing as an indentation resulting from an expansion scab.

BURN ON – Adhesion of sand to the casting, usually due to the metal penetrating into the sand.

BURN OUT – Usually refers to the removal of the disposable wax or plastic pattern in the investment moulding process by heating the mould gradually to a sufficiently high temperature to consume any carbonaceous residues.

BUTT RAMMAR – The flat end of the moulders rammer.

BABBITT METAL – White metal bearing alloy, suitable for bearings subjected to moderate pressures, contains tin 59.5% min, copper 2.25- 3.75%, antimony 9.5-11.5%, lead 26% min, iron 0.08% max, bismuth 0.08% max.

BACKING SAND – Foundry sand placed next to the facing sand after the latter is in place. It forms the bulk of sand used to complete the mould.

BAINITE – A structure in steel named after E.G. Bain that forms between 481° C and the M’s temperature. At the higher temperatures, it is known as upper or feathery bainite. At the lower temperatures it is known as lower or a acicular bainite and resembles martensite.

BAKELITE – Trade name for one of the first used thermo-setting synthetic resins. It is derived from the name of the inventor Dr. L.H. Backeland, and its formation is the result of a chemical action between formaldehyde and phenol.

BAR – A piece of material thicker than sheet, long in proportions to its width or thickness, and whose width to thickness ratio is much smaller than sheet or plate, as low as unity for squares and rounds.

BARK – The decarburized layer just beneath the scale that results from heating steel in an oxidizing atmosphere.

BASE METAL – Metal present in the alloy in largest proportion.

BEARING METALS – Metals (alloys) used for that part of a bearing which is in contact with the journal e.g., bronze or white metal, used on account of their low coefficient of friction when used with a steel shaft.

BELFAST SAND – Red moulding sand of fine grain, and good bonding qualities with moderate refractoriness, suitable for use as facing sand.

BELL METAL – High tin bronze, used in the casting of bells, which is composed of up to 30% tin, together with some zinc and lead

BESSEMER STEEL – Steel manufactured in a Bessemer converter, and sometimes referred to as mild steel.

BILLET – A solid semi finished round or square product that has been hot worked by forging, rolling or extrusion.

BLUE VITRIOL – A chemical mixture of copper sulphate, water and sulphuric acid. Applied to polished metal for layout purposes, it turns to copper colour.

BOND – In grinding wheels and other relatively rigid abrasive products, the material that holds the abrasive grains together. In welding, the junction of joined parts.

BORON CARBIDE – An abrasive used in cutting tools, a compound whose chemical formula is B4 C and obtained from boron trioxide (B2O3) and coke at a temperature of 2500°C. Fine powder as hard as diamond.

BRASS – A range of copper zinc alloys, usually those containing 55-80% copper. Alloys containing not less than 63% of copper are called ALPHA BRASSES. When less than 63% of copper is present, the alloy is called ALPHA-BETA alloy.

BRAZING ALLOY – Copper zinc alloy, which sometimes includes small percentages of tin, and lead, used for brazing, the melting point of which is governed by the percentage of zinc.

BRINE – Water that has been saturated or nearly saturated with salt.

BRIQUETS – Compact cylindrical or other shaped blocks formed of finely divided materials by incorporation of a binder, by pressure, or both.

Materials may be ferroalloys, metal borings or chips, silicon carbide etc.

BRONZE – A copper rich, copper tin, copper lead or copper beryllium alloy to which often alloying elements (phosphorous, aluminium, zinc, silicon) may be added. Usually bronze is a copper tin alloy containing 90% copper and 10% tin.

BUILDING BRICK – These are made from clay. Generally, the clay is mixed with water to a plastic state and extruded in a column that is wire-cut crosswise to the desired size. Occasionally the dry pressing process is used.

BALL BEARING – An antifriction bearing where the rolling elements are spherically shaped. Bearing consists of an inner and outer hardened steel races separated by a series of hardened steel balls.

BATH LUBRICATION – Lubrication system in which the bearing contains a space filled with oil, which is in contact with a portion of the journal.

BEARING – The part which transmits the load to the support and in so doing, takes the friction caused by the moving parts in contact. Area of the unit in which the contacting surface of a revolving part rests.

BEARING CAPS – On an engine, caps held in place by bolts or nuts which, in turn, hold bearing halves in place.

BEARING CRUSH – The additional height over a full half which is purposely manufactured in each bearing half. This ensures complete contact of the bearing back with the housing bore when the unit is assembled.

BEARING FAILURE – Failure of a bearing due to continued flexing of the bearing surface from the applied load.

BEARING OIL CLEARANCE – The space purposely provided between the revolving shaft and the bearing in which it rotates. Through this space lubricating oil can flow.

BEARING PRELOAD – Amount of static pressure exerted on a bearing or a set of bearings. Preload is usually adjusted by a threaded collar or shims.

BEARING PRELUBRICATOR – A special tank attached to an airline which supplies oil at a predetermined and maintained pressure to the engine lubricating system when the engine is not operating.

BEARING SPACER – A piece of tubing used between the two wheel bearing inner races to prevent unwanted bearing preload as the axle is tightened.

BEARING SPIN – A type of bearing failure caused by lack of lubrication which overheats the bearing while the crankshaft is still in place.

BEARING SPREAD – A purposely manufactured small extra distance across the parting faces of the bearing half in excess of the actual diameter of the housing bore.

BYPASS FILTER – An oil filter that constantly only filters a portion of the oil flowing through the engine or machine.

BOUNDARY FRICTION – The resistance to relative motion when one solid surface is caused to move tangentially over another, the surfaces being covered only by an adsorbed contamination film.

BOUNDARY LUBRICATION – Type of lubrication in which the two surfaces have between them a more or less complete layer of oil which is only, at the most, a few molecules thick.

BUSHING – A member that takes up space and usually allows movement at the attachment point. A one piece replaceable sleeve placed in a bore to serve as a bearing surface. Bearing for shaft, spring shackle, piston pin etc. A metallic or synthetic lining for a hole.

BACKFIRE (exhaust system) – Passage of unburned air fuel mixture into

the exhaust system where it is ignited by some hot spot and causes a

loud explosion.

BALANCED DRAFT – A boiler using both forced draft fan and induced

draft fan, can be regulated and balanced in the amount of air and flue

gases handled so that the furnace pressure is almost atmospheric.

BAGASSE – A fuel produced as a by product of the abstraction of juice

from sugar cane. The dried cane (fibrous residue) is usually fed into a

specially designed furnance by means of overfeed stokers.

BENCH – The name applied to a complete plant for the manufacture of

coal gas. Also called RETORT BENCH.

BENZOL – Crude benzene, used as a motor spirit, generally mixed with

petrol, and valued for its antiknock properties.

BIOGAS – Obtained by fermentation in the sewage disposal system, or by fermentation of cattle waste, farm waste etc.

BIOSPHERE – The portion of earth and its atmosphere that can support life.

BLAST FURNANCE GAS – A gas of low calorific value, a by product of iron smelting due to burning of coke in the furnace with limited air, used for preheating the blast, for steam raising etc. It may contain up to 30% carbon monoxide.

BLAST MAIN – The main blast air pipe supplying air to a furnace.

BLOW BY – Leakage of unburned air fuel mixture and some burned gases past the piston rings into the crankcase during the compression and

combustion strokes.

BLOW TORCH EFFECT – In gas or oil burning furnaces, when the flame impinges on any surface, such as a tube or refractory wall, that surface is burned as by a blow torch. This is a combustion condition to be avoided as destructive to the surface.

BLUE WATER GAS – A mixture of approximately equal proportions of carbon monoxide and hydrogen made by passing steam over incandescent coke in special generators.

BOILING POINT – The temperature at which a liquid begins to boil.

BOMB CALORIEMETER – An apparatus used for determining the calorific values of fuels. The bomb consists of a thick walled steel vessel in which a weighed quantity of fuel is ignited in an atmosphere of compressed oxygen. The bomb is immersed in a known volume of water; from the rise of temperature of water the calorific value is calculated.

BOTTLED GAS – LPG (liquefied petroleum gas) compressed into strong metal containers. Gas when confined in tank, under pressure, is in the liquid form.

BRIQUETS – Coherent masses of uniform size made by the application of pressure to any powdery material placed in a suitable mould with or without a binder.

BUTANE – A hydrocarbon gas formed synthetically, by the action of zinc or ethyl iodide. Petroleum gas, that is liquid, when under pressure. Often used as engine fuel in trucks.

BLADES or BUCKETS – The parts that form the rotor flow passages and serve to change the direction, and hence the momentum, of the fluid received from the stationary nozzles.

BLADE SPEED RATIO – Ratio of mean blade speed to the absolute velocity of the fluid stream at the blade inlet.

BOUNDARY LAYER – A thin layer of fluid adhering to a surface, when the fluid flows along the surface, in which there is a steep velocity gradient due to viscous friction, the velocity dropping to zero at the boundary surface.

BRAYTON CYCLE – Basic cycle for gas turbines. The cycle in which air is compressed isentropically, heated at constant pressure and expanded isentropically thus delivers work until the low pressure is reached and then heat is rejected. Also called JOULE CYCLE.

BLACK OXIDE COATING – Coating produced by converting the surface of iron or steel to black iron oxide having a thickness of about 0.0025 mm.

BACK PRESSURE – A pressure exerted by a fluid contrary to the pressure producing the main flow. For example, pressure in the exhaust manifold, the higher the back pressure, greater is the resistance to flow of exhaust gases through the exhaust system. This lowers volumetric efficiency.

BARREL – Refers to the cylinders in an engine or to the number of throttle bores in a carburettor.

BARREL TYPE CRANKCASE – A petrol engine crankcase so constructed that the crankshaft can be removed from one end, in more normal construction, the crankcase is split.

BASE CIRCLE – As applied to camshaft, lowest spot on the cam. Area of cam that is directly opposite lobe.

BELLOWS – A device, usually metal that can lengthen or shorten much like an accordion. Some cooling system thermostats are of bellows type.

BIMETAL – A thermostatic bimetal element made up of two different metals with different heat expansion rates. Temperature changes produce a bending or distortion movement of the element.

BLOCK (engine) – Basic part of the engine casting containing cylinders.

BLOWBY – Piston rings do not effectively seal compression pressure, and as such allows hot gases to blow between rings and cylinder wall into the crankcase. This causes overheating of piston and poor performance.

BLOWER – Supercharger or engine intake air compressor, a low pressure air pump, usually rotary or centrifugal type.

BLUE PRINTING (engine) – Dismantling the engine and reassembling it to exact specifications.

BOOST – The amount by which the induction pressure of a super charged internal combustion engine exceeds atmospheric pressure, expressed in kg/sq.cm.

BORE – A cylinder, hole, or the inside diameter of the cylinder or hole. May refer to cylinder itself or to diameter of the cylinder.

BORE DIAMETER – Diameter of a hole or a cylinder.

BORING – Renewing or enlarging cylinders by cutting and honing them to a specified size. Boring bar is used to make the cut.

BORING BAR – Tool used to cut engine cylinders to specific size. As used in garages, to cut worn cylinders to a new diameter.

BOTTOM DEAD CENTER (BDC) – Lowest position of the piston in the cylinder.

BOXED I ROD – Connecting rod in which I beam section has been stiffened by welding plates on each side of the rod.

BRAKE HORSE POWER (BHP) – Actual usable power delivered by an engine at the crankshaft for driving a vehicle or any other unit. Computed using the engine coupled to a dynamometer.

BRAKE MEAN EFFECTIVE PRESSURE (BMEP) – Mean effective pressure (imaginary) which when assumed to be acting on the piston during the power stroke would result in the given brake horse power output. Equal to mean indicated pressure times mechanical efficiency.

BRAKE THERMAL EFFICIENCY – Ratio of heat equivalent of power output in the form of brake horse power to the corresponding heat input from fuel.

BREAKIN – Period of operation between installation of new or rebuilt parts and when the parts are worn to the correct fit. Driving at reduced and varying speed for a specified distance or duration permits parts to wear out to the correct fit.

BREATHER PIPE – A pipe opening into the interior of an engine i.e., crankcase. Used to assist ventilation.

BTDC – Before top dead center, also called BUDC-before upper dead center.

BORING BAR MICROMETER – On boring operations, it is often necessary to adjust the cutter setting by a few thousandths of an inch. With this, it is possible to determine exactly the depth of cut taken.

BACK GEARS – Gears applied to machine tools to increase the number of speed changes obtainable with a cone or step pulley belt drive.

BASTERED THREAD – A screw thread which does not confirm to any recognized standard dimensions.

BED – One of the principal parts of a machine tool having accurately machined ways or bearing surfaces for supporting and aligning other movable parts of the machine.

BELLCHUCK – Hollow cylindrical chuck bolted to the main chuck for the purpose of giving additional support to work of awkward shape.

BELT SHIFTER – A flat hardwood strip of suitable length having shifter fingers attached at one end and used to shift a belt from one pulley to another or to replace a belt which has run off a pulley on an overhead drive shaft.

BOLSTER – Support for dies and tools in forging presses and drop stamps.

BOX ANGLE PLATE – An angle plate made of cast iron, usually with slots cast in it and accurately machined on the outside.

BOX JIG – A jig made in the form of a box into which the job to be drilled is inserted.

BULL WHEEL – The large gear wheel of a planer which meshes with the rack under the table and drives it. The large crank gear of a shaper is often called a bull wheel.

BAFFLE – A device which slows down or diverts the flow of gases, liquid, sound etc.

BASIC SIZE – The theoretical or nominal standard size from which all variations are made.

BASTARD – Not standard, irregular. A bastard cut file is a rough cut file having coarse teeth than a second cut file.

BELL MOUTHED HOLE – A hole which is rounded or tapered slightly larger at one end or both ends and is not exactly cylindrical throughout its entire length.

BEVEL – Any surface not at right angle to the rest of the work-piece. If a bevel is at a 45° angle, it is frequently called a MITER.

BIMETALLIC STRIP – A strip of metal consisting of one metal (or alloy) in the top portion bonded to a different metal in the bottom portion. A straight strip becomes curved when heated.

BLIND HOLE – A hole which is made to a certain depth of a work-piece but does not pass through it.

BISECTING AN ANGLE – Dividing an angle into two equal parts.

BOND – Holding together of different parts.

BORE – The inside diameter of a cylinder, or a hole for a shaft. Also the operation of machining a circular hole in a metal work-piece

BRUSH – Pieces of carbon or copper that make a sliding contact against the commutator or slip rings.

BACKLASH – The clearance or amount of movement between the tooth profiles of a pair or train of gears in mesh. Also refers to the looseness or lost motion between screw threads which have been badly worn.

BABCOCK AND WILCOX MILL – Dry grinding mill using rotary steel balls.

BALANCE BOX – A box, filled with heavy material used to counter balance the weight of the job and load of a crane of the cantilever type.

BALANCE CRANE – A crane with two arms, one having counterpoise arrangements to balance the load taken by the other.

BALANCING MACHINE – A machine for testing the extent to which a revolving part is out of balance, and to determine the weight and position of the masses to be added or removed, to obtain balance.

BAND SAW – A narrow endless strip of saw blading running over and driven by pulleys, as a belt used for cutting wood or metal to intricate shapes.

BAR LATHE – A small lathe of which the bed consists of a single bar of circular, triangular or rectangular section.

BATTERY – An electrochemical device for storing energy in chemical form so that it can be released as electricity. It is a group of electric cells connected together.

BED PLATE – A cast iron or fabricated steel base, to which the frame of an engine or other machine is attached.

BENCH LATHE – A lathe of small dimensions that can be mounted on a bench or stand.

BENDING MACHINE – Machine designed to bend and fold sheet metal.

BLOWER – A low pressure air pump, usually of one rotary or centrifugal type.

BOARD DROP STAMP – A stamping machine in which the frictional grip of opposed rollers on either side of a vertical board lifts a tap, which falls when the roller pressure is released.

BOLT MAKING MACHINE – A machine which forges bolt by forming a

head on a round bar.

BOOST FAN – A fan for restoring the pressure drop of air or gas, used for restoring the pressure drop in transmission pipes, and for supplying air to furnaces.

BORING AND TURNING MILL (vertical) – Machine designed for boring and turning castings and forgings.

BORING MACHINE (horizontal) – Machine used for boring, the spindle being horizontal. In one type, the spindle only rotates and in another type the spindle rotates and also has a horizontal movement.

BORING MACHINE (vertical) – Machine used for boring, the spindle being vertical, very similar to a radial driller. Also called BORING MILL.

BRASS FINISHERS LATHE – Lathe specially designed with attachments to machine brass work in quantities. The chief feature is the provision of special hand operated rests.

BREAK LATHE – Heavy lathe with sliding bed to accommodate large work. The machine comprises a fast and a loose head stock, and a base plate upon which the bed is mounted.

BROACHING MACHINE – Machine designed to drive a tapered tool of special form, known as a broach, through a hole or over a piece of work, which bring the hole or the surface to the desired finished size.

BAND or BELT CONVEYOR – An endless band passing over, and driven by horizontal pulleys, thus forming a moving track which is used to convey loose material or small articles.

BALANCED LUFFING – Luffing mechanism, in which the moment due to the weight of the jib is at balance with the moment produced by the counterweight.

BARGES AND LIGHTERS – Shallow draft, box like vessels used for cargo transport in protected waters such as bays, rivers and canals.

BARREL ELEVATOR – This comprises parallel travelling chains, with curved arms projecting. The chains pass over sprocket wheels at the top and bottom of the elevator, and lift barrels from a loading platform to a runway.

BARREL HOPPER – A machine for unscrambling, orientating and feeding small components during a manufacturing process, in which a revolving barrel tumbles the components onto a sloping, vibrating feeding blade.

BAY – An area used for the open storage of heavy items.

BELT CONVEYOR – A conveyor which consists of a belt of suitable material such as rubber, canvas, balata etc., running over a pair of end drums or pulleys and supported at intervals by a series of rollers called idlers, these in turn being supported on a conveyor frame.

BELT CONVEYOR IDLERS – Number of idler rolls provided between the terminal pulleys to prevent the belt from sagging due to gravity and under the load.

BELT CONVEYOR PULLEYS – Wheels used to support and drive the belt. They include drive, terminal or bend, take up and snub pulleys.

BIN – An enclosed space for storing certain types of goods.

BIN TICKET – Tickets attached to storage places to provide information on the quantity of goods received, issued and on hand.

BRACING – Securing the contents of a shipment to prevent shifting and damage.

BRAKE – Arrangement in the hoisting machinery to stop the load and hold it when applied to the hoisting motion or bring the relevant mechanisms at rest within specified braking distances. May be a band brake, disc brake or a cone brake.

BUCKET ELEVATOR – Conveyor equipped with buckets which carry bulk material in the vertical or near vertical direction, loading is at the bottom and discharging is at the top.

BULK COMMODITY TRUCK – Trucks used to transport loose bulk materials, such as sand and gravel.

BUCKET OR SKIP HOISTS – Hoisting equipment for handling of bulk materials in self dumping buckets or skips.

BULLDOZER – A pendant attachment mounted on crawler and wheel tractors, that strips off soil surface and transports it to the required spot.

BANDED STRUCTURE – A segregated structure of nearly parallel bands aligned in the direction of working.

BEL – A unit denoting the ratio of power levels of signals or sound. The number of bells may be given as the common logarithm of the ratio of powers.

BETA RAY – A ray of electrons emitted during the spontaneous disintegration of certain atomic nuclei.

BOILING POINT – The temperature at which a liquid begins to boil.

BOUND ELECTRONS – The inner orbit of electrons around the nucleus of the atom.

BREAKING POINT – The final rupture of a material which is being pulled in tension, after it has reached its ultimate strength.

BRINELL HARDNESS – The hardness of metal or alloy measured by pressing a hard ball (usually 10 mm diameter) with a standard load into the specimen. A number is derived by measuring the indentation with a special microscope.

BRITTLE METAL – A metal which exhibits only a very small change in dimensions before it fractures.

BRITTLENESS – The property of materials to not deform under load, but to break suddenly, for example, cast iron and glass are brittle. Brittleness is opposite to plasticity.

BULK MODULUS OF ELASTICITY – Ratio of a uniform, triaxial (equal in all directions) tensile or compressive stress to the change in volume it produces.

BEADING – Process of forming a bead or lapped edge on a sheet metal article.

BENDING (by forging) – In bending there is a thinning of the material, accompanied by a spreading of the metal on the inside of the bend and a narrowing at the outside.

BLANKING – Cutting or shearing a shape (called blank) with a die from sheet metal stock. The whole material is saved and used for further operation.

BLAST CLEANING – Blast cleaning involves the forcing of a stream or spray of sand or other abrasive material against the surface of metal, stone, and other materials by means of compressed air.

BORING – Opening out or increasing the diameter of an existing drilled or cored hole by means of a boring tool.

BRAZING – Joining two pieces of metal without melting either one by using a brazing alloy (copper zinc alloy i.e., brass) that melts at a lower temperature than the materials being joined.

BROACHING – Consecutive shearing of a hole or contour by a series of stepped cutting edges similar to a saw used in low acting presses for accurate sizing of holes or contours, such as gear teeth, and keyways.

BURNISHING – Bright, polished finish produced on the surface of a metal by rubbing it with another metallic harder surface, which smoothes out small scratch marks.

BUTT-WELDING – Form of electrical resistance welding, the passage of current between the ends of the sections to be joined causing a rise in temperature sufficient to fuse the metal.

BEVEL GEARING – Gearing arrangement in which the axes of the shafts connected by gears intersect.

BASIC REFRIGERATION CONTROL – Device that starts, stops, regulates and/ or protects the refrigeration system and its components.

BAUDELOT EVAPORATOR – An open type of cooler in which the liquid to be cooled flows from distributing troughs or headers over a cooling surface consisting of sets of grids or a pair of stamped corrugated metal sheets forming channels.

BLEEDER – A pipe sometimes attached to a condenser to lead off liquid refrigerant, parallel to the main flow.

BRINE – Any liquid cooled by the refrigerating system and used for the transmission of heat.

BRINE SYSTEM COOLING – Any system whereby brine, cooled by a refrigerating system, is circulated through pipes to the point where the refrigeration is needed.

BUTANE – A hydrocarbon, flammable refrigerant used to a limited extent in small units.

BACKFIRE – (1) Premature ignition during starting of an internal combustion engine, resulting in an explosion before the end of compression stroke, and consequent reversal in the direction of rotation. (2) An explosion of live gases accumulated in the exhaust system due to incomplete combustion in the cylinder.

BACKFIRE (intake system) – Pre-explosion of air fuel mixture so that the explosion passes the open intake valve and flashes back through the intake manifold. May be caused by faulty timing, crossed plug wires, leaky intake valve etc.

BACK KICK – Violent reversal of an internal combustion engine crankshaft rotation, during starting due to backfire.

BALANCED CARBURETTOR – Carburettor in which the float bowl is vented into the air horn, below the air cleaner, to compensate for the effects of a clogged air filter.

BATTERY COIL IGNITION – High tension supply for sparking plugs, in automobiles, in which the interruption of a primary current from a battery induces a high secondary emf in another winding on the same magnetic circuit, the high potential being distributed in synchronism with the contact breaker in the primary circuit and the engine firing order.

BERNOULLIS PRINCIPLE – Given a fluid flowing through a tube, any constriction or narrowing of the tube will create an increase in the fluid velocity and a decrease in pressure. This principle is used in the venturi tube of the carburettor.

BOOST VENTURI – also called secondary venturi is a smaller venturi or restriction, incorporated in some carburettors in the middle of the primary venturi. It increases air speed, vacuum created and hence fuel flow.

BOWL VENT – is an opening in the carburettor float chamber. This hole prevents pressure or vacuum from building up in the bowl.

BREAKER ARM – The movable arm upon which one of the breaker points of the ignition system is affixed.

BREAKER POINTS (ignition) – Pair of points, one fixed and another movable, that are opened and closed to break and make the primary circuit. When the circuit is broken by opening the points, the spark plug fires.

BUTTERFLY VALVE – A type of valve used for choke and throttle valve in a carburettor that is so named due to its resemblance to the insect of same name. This valve controls charge flow.

BABCOCK and WILCOX BOILER – A water tube boiler consisting in its simplest form of a horizontal drum from which is suspended a pair of headers carrying between them an inclined bank of straight tubes.

BAG – A bulged out section of a portion of the shell, extending through the full thickness of the shell, caused by overheating and pressure.

BALANCED DRAUGHT – A system of air supply to a boiler furnace, in which one fan forces air through the grate, while a second, situated in the uptake, exhausts the flue gases. The pressure in the furnace is thus at atmospheric i.e., is balanced.

BANKING LOSS – The fuel used in maintaining a floating bank or to maintain a dead bank and then raise the steam pressure to normal.

BANKING UP – Reducing the rate of combustion in a boiler furnace by covering the fire with slack or fine coal.

BENSON BOILER – A high pressure boiler of the once through type in which water is pumped through the successive elements of the heating surface, firing being by gas, oil, or pulverized coal.

BLISTER – A separation of the metal from the shell plate, caused by impurities rolled into the shell plate when formed.

BLOWDOWN OF SAFETY VALVE – The difference between the pressure at which the safety valve pops and that at which it closes.

BLOWING OFF – Act of letting out water and steam from a boiler to carry off accumulated mud and scale.

BLOW OFF VALVE – The valve which empties the boiler for cleaning, inspection, or repair. It blows out mud, scale, or sediment when the boiler is in operation and prevents excessive concentration of soluble impurities in the boiler. Also used for rapid lowering of boiler water level if it is too high.

BOILER – A closed pressure vessel in which a fluid is heated and converted to vapour for use external to itself, by the direct application of heat resulting from the combustion of fuel (solid, liquid or gaseous) or by the use of electricity or nuclear energy.

BOILER CAPACITY –The weight of steam, usually expressed in kg/hour, which a boiler can evaporate, when steaming at full load output.

BOILER COMPOSITION – Chemicals introduced into the boiler feed water to inhibit scale formation and corrosion, or to prevent priming or foaming.

BOILER CROWN –The upper rounded plates of the boiler of shell type.

BOILER EFFICIENCY – The ratio of heat supplied by a boiler in heating and evaporating the feed water to the heat supplied to the boiler in the fuel. It may vary from 60 to 90 per cent.

BOILER PATCH – A small piece of metal used to cover and strengthen a weak spot. A soft patch is a covering over a leak or defect which is fastened with bolts, as distinguished from a hard patch which is riveted.

BOILER PLATE – Mild steel plate, generally produced by the open hearth process, used mainly for the shells and drums of steam boilers.

BOILER PRESSURE – The pressure at which steam is generated in a boiler.

BOILER SETTING – The supporting structure on which a boiler rests, usually of brick for land boilers and steel for marine boilers.

BOILER TEST – (1) A hydraulic pressure test applied to check water tightness under pressure greater than the working pressure. (2) An efficiency test carried out to determine evaporative capacity and magnitude of losses.

BOILER TRIAL – An efficiency test of a steam boiler, in which the weight of feed water and of fuel burnt are measured and various sources of losses are assessed.

BOILER TUBES – Steel tubes forming part of the heating surface in a boiler. In water tube boilers, the hot gases surround the tubes. In locomotive and some marine boilers (fire tube boilers) the gases pass through the tubes.

BREECHING – The metal duct that carries the smoke and gases of combustion from a furnace to the stack or chimney for ultimate discharge to the atmosphere.

BACK PRESSURE TURBINE – A steam turbine from which the whole of the exhaust steam, at a suitable pressure, is taken for heating purposes.

BAROMETRIC CONDENSER – A high level jet condenser.

BASTERED CONDENSER – It is an atmospheric keel condenser, which are sometimes fitted to canal boats or other sea vessels.

BINARY VAPOUR ENGINE – A heat engine using two separate working fluids, generally mercury vapour and steam, for the high and low temperature portions of the cycle respectively, thus enabling a large temperature range to be used, with improved thermal efficiency.

BLADE – Part attached to the rotating element of the machine or rotor, in which the stream of steam particles has its direction and hence its momentum changed. Also called DEFLECTOR.

BLADE VELOCITY COEFFICIENT – The ratio of the relative velocity of steam at outlet to the relative velocity at inlet of the blade.

BLANK FLANGE – A disc, or solid flange, used to blank off the end of a pipe.

BLAST PIPE – The exhaust steam pipe in the smoke box of a locomotive, which terminates in a nozzle to provide draft by entraining the flue gases in the steam jet and exhausting them through the chimney.

BLEEDING – A method of improving the thermal efficiency of steam plant by withdrawing a small part of the steam from the higher pressure stages of a turbine to heat the boiler feed water.

BLEEDER TURBINE – A steam turbine in which the steam is extracted at one or more intermediate stages for industrial use, often at comparatively high pressure.

BYPASS GOVERNING – Governing arrangement in which part of the steam that enters the turbine is bypassed depending upon the extent of load reduction.

BASIC UNITS – are length, mass, time, temperature and angle.

BLACK BODY – A body which absorbs all the radiation falling on it i.e., has a non-reflecting surface. A black body emits the maximum amount of radiation possible at a given temperature, and the amount is proportional to the fourth power of the absolute temperature.

BOILING POINT – The temperature at which a liquid boils for any given surrounding atmospheric pressure. Now the saturation pressure of the vapour equals that of the atmosphere.

BOUNDARY – is a real physical surface or an imaginary surface enclosing some matter. The boundary may be a fixed one or a varying one.

BOYLE’S LAW – The absolute pressure of a gas will vary inversely as the volume, if the temperature remains constant. Or conversely, the volume will vary inversely as the absolute pressure, if the temperature remains constant.

BRAKE HORSE POWER – Useful power available from an engine. Also called SHAFT HORSE POWER.

BACK BONE FRAME – Frame which uses the engine as a structural member for load carrying.

BEAD – The portion of the tyre which holds it onto the rim.

BEZEL – Piece of metal surrounding head lights, gauges or similar components, sometimes used to hold the glass face of a gauge in the dashboard.

BOOSTER PORT – In a two stroke engine, the port that allows an extra amount of air fuel mixture from the intake port into the combustion chamber.

BRAKE ACTUATOR CAM – Small cam that pivots in brake backing plate and forces brake shoes into brake drum.

BRAKE CALIPER – Part of a disc brake which holds friction pads and encloses disc. As the brake is applied, hydraulic fluid forces a piston in caliper towards disc, causing disc to be pinched between brake pads.

BRAKE DISC – A round, flat disc made of steel or cast iron. It is mounted on outside of wheel hub.

BACK BONE FRAME – Frame which uses the engine as a structural member for load carrying.

BEAD – The portion of the tyre which holds it onto the rim.

BEZEL – Piece of metal surrounding head lights, gauges or similar components, sometimes used to hold the glass face of a gauge in the dashboard.

BOOSTER PORT – In a two stroke engine, the port that allows an extra amount of air fuel mixture from the intake port into the combustion chamber.

BRAKE ACTUATOR CAM – Small cam that pivots in brake backing plate and forces brake shoes into brake drum.

BRAKE CALIPER – Part of a disc brake which holds friction pads and encloses disc. As the brake is applied, hydraulic fluid forces a piston in caliper towards disc, causing disc to be pinched between brake pads.

BRAKE DISC – A round, flat disc made of steel or cast iron. It is mounted on outside of wheel hub.

BRAKE DRUM – A circular ring of cast iron that is part of wheel hub. It provides a place for brake lining to be applied.

BRAKE FADE – Loss of braking power, usually caused by excessive heat after repeated brake applications.

BRAKE LINE – Special hydraulic tubing made of steel, plastic or reinforced rubber. Hydraulic lines must be capable of withstanding extreme pressure without deforming.

BRAKE LINING – A special high friction material made of asbestos and other materials bonded to brake shoes and brake pad plates. Brake lining produces friction and heat when it is forced against brake drum.

BRAKE PAD – The friction pad on a disc brake system.

BRAKE SHOE – The friction lining on a drum brake system.

BRAKE WEAR INDICATOR – Index grooves, tabs, or reference lines to indicate amount of brake lining or pad wear.

BRIDGED PORTS – A vertical port division in a two stroke cycle engine cylinder which allows use of a large port without the danger of ring or piston catching.

BACKHAND WELDING – A welding technique in which the welding torch or gun is directed opposite to the progress of welding.

BACK WELD – A weld deposited at the back of a single groove weld.

BARE ELECTRODE – A filler metal electrode of a single metal or alloy, produced into a wire, strip or bar form and without any coating or covering on it.

BARE METAL ARC WELDING – Process which produces coalescence of metals by heating them with an electric arc between a bare or lightly coated metal electrode and the work piece.

BASE METAL – The metal to be welded, brazed, soldered or cut.

BLIND JOINT – A joint, no portion of which is visible.

BORAX – is the old standard flux for brazing, exists in two forms—ordinary borax and amorphous or fused borax.

BRAZING – A group of welding processes that produces coalescence of materials by heating them to the brazing temperature, using a filler metal having a liquidus above 450°C and below the solidus of the base metal.

BUTT JOINT – A joint between two members aligned approximately in the same plane.