LATERAL LOAD (tyre) – The force on the side of the tyre treads.
LEADING SHOE – A brake shoe that has the drum rotating from the toe toward heel.
LEADING TRAILING BRAKE – A drum brake assembly having one shoe energized in either forward or rearward wheel rotation.
LEAF SPRING – A spring made up of a series of flat steel plates of graduated length, assembled one on top of another.
LEVEL CONTROL (automatic) – A suspension system which compensates for variations in load in the rear of the car, positioning the rear at a predesigned level regardless of load.
LIMITED SLIP DIFFERENTIAL – A differential allowing unequal torques to be delivered to the axle shafts.
LINKAGE POWER STEERING – A type of power steering in which the power steering units (power cylinder and valve) are an integral part of the steering linkage.
LORD LEVELING SYSTEM – A system used to level a vehicle that is heavily loaded.
LORD RANGE (tyre) – The amount of weight that can be safely carried by a tyre. It indicates the number of plies at which a tyre is rated. Load range B equals 4 ply rating, C equals 6 ply rating, and D equals 8 ply rating.
LUG – The flange stud on an axle or hub on which the drum and wheel are fastened.
LADLE – Metal receptacle lined with refractory for transportation of molten metal.
LOAM – A course, strongly bonded moulding sand used for loam and dry sand moulding.
LOAM MOULDING – A system of moulding especially for large castings, wherein the supporting structure is constructed of brick. Coatings of loam are applied to form the mould face.
LACQUER – A quick drying automotive paint.
LAMELLAR – An alternating plate like structure in metals (as in pearlite).
LAMINATE – (1) A composite metal, usually in the form of sheet or bar, composed of two or more metal layers so bonded that the composite metal forms a structural member. (2) To form a metallic product of two or more bonded layers.
LAMINATIONS – Metal defects with separation or weakness generally aligned parallel to the worked surface of the metal.
LASER – Light Amplification by Simulated Emission of Radiation. A device in which heat is derived from the intense coherent beam of laser light energy. This intense, narrow beam of light is used in some welding and machining operations.
LEAD – Heavy, bluish grey, soft, ductile metal, which has a specific gravity of 11.3 and a melting point of 327°C, extensively used alone, and as the basis of many antifriction alloys.
LEAD SCREEN – In radiography, a screen is used (1) to filter out soft wave or scattered radiation and (2) to reduce the intensity of the remaining radiation so that the exposure time can be decreased.
LEDEBURITE – The eutectic of the iron carbon system, the constituents being austenite and cementite. The austenite decomposes into ferrite and cementite on cooling below the transformation temperature.
LIGNIN – A substance that is related to cellulose, that with cellulose forms the woody cell walls of plants and the material that cements them together. Methyl alcohol is derived from lignin in the destructive distillation of wood.
LOAM – Clayey sand mixture having the consistency of slime, and used in the making of moulds and cores for heavy castings.
LOW CARBON STEEL – Steel containing less than 0.3% carbon.
LUTE – Fine adhesive composition of substances such as clay, sharp sand, plumbago and horsedung tempered with water. Used for sealing joints in moulds and cores, for the purpose of making them air or metal tight.
LAWS OF FRICTION – The force of friction is (1) directly proportional to the pressure between the surfaces in contact, (2) independent of the extent of the surfaces in contact and (3) independent of the velocity of sliding.
LOAD MOTION – Rolling or sliding motion found at the bearing surfaces.
LUBRICANT – A fluid having two essential properties namely viscosity and oiliness, and used to reduce friction.
LUBRICATING FILM – A thin coating of lubricant (oil) which prevents contact between moving parts.
LUBRICATING SYSTEM – The system in the engine that supplies lubricating oil to the moving engine parts, to prevent actual contact between the moving surfaces.
LUBRICATION – Use of lubricant (oil or grease) to reduce friction.
LIGNITE – A coal of high moisture content and low calorific value, generally less than 8300 BTU/lb. May require predrying before being used as a fuel.
LIQUID ASH REMOVAL SYSTEM – An arrangement of piping by which molten ash is removed continuously or intermittently, as desired, from the bottom of a furnace. The operating medium is usually compressed air with pneumatic controls.
LIQUEFIED PETROLEUM GAS (LPG) – A gas fuel that is stored in liquid form and is converted into gas as it leaves the storage tank by a pressure regulator that steps down the storage pressure on the liquid at the tank outlet and thereby permits the liquid to assume its normal gaseous state at the existing temperature and reduced pressure.
LONG FLAME BURNER – An oil or gas burner in which the mixture of fuel and air is delayed long enough to produce a long flame from the burner nozzle. Can be a source of trouble if the flame impinges on either refractory or tube surfaces.
LOWER HEATING VALUE – Net heat liberated per kg of fuel after the heat necessary to vaporize and superheat the steam formed from the hydrogen (and from the fuel) has been liberated.
LOW LEAD FUEL – Gasoline which is low in tetraethyl lead (approximately 0.5 gm per gallon).
LACING WIRES – Wires called lacing wires or lashing wires are used to keep long blades in alignment and to add stiffness.
LEAKAGE LOSSES – Energy loss due to leakage of the working fluid in turbines, between stages, past the shaft and around the balance piston.
LACQUERING – A protective coat given to an article to prevent the polished surface from tarnishing, to prevent oxidation or to improve the general appearance and make the article more pleasing to the eye, and hence more saleable.
L HEAD ENGINE – A type of engine with valves located in the cylinder block, the combustion chamber is L shaped.
LIGHT LOAD TEST – The test applied to storage batteries during which the voltage is measured while the battery is subjected to a light load, such as the car head lights.
LIQUID COOLED ENGINE – An engine that is cooled by the circulation of the liquid coolant around the cylinders.
LOAD TEST – A cranking motor test to measure the current drawn under normal cranking load.
LEVEL, HYDROSTATIC – U tube device employed during the levelling and setting of work too long for the use of a spirit level.
LEVEL, SPIRIT – Instrument consisting essentially of a small sealed glass tube containing spirit (alcohol or ether) so mounted that the enclosed bubble of air occupies a central position only when the instrument is placed horizontally.
LIMIT GAUGE – A gauge that represents a limiting (maximum and minimum) size within which the work will be acceptable.
LADLE – Receptacle used for transporting molten metal.
LATHE CARRIER– It is clamped on a bar and engaged with a projecting dog on the catch plate fitted to the lathe head stock. This enables the bar to revolve between the centres.
LATHE CENTERS – Solid steel pieces which have a tapered shank and 60° pointed end. A live center fits into the headstock spindle and a dead center fits into the tailstock spindle to support and provide bearing points for the work turned between centers.
LAYOUT PLATE – A smooth finished flat steel plate on which work and tools may be placed and used while laying out a job.
LEAD SCREW – Master screw used for cutting a screw thread in a lathe.
LIVE CENTER – A lathe center that fits into the headstock spindle and so named because it revolves.
LEVER – A simple machine for obtaining mechanical advantage. The lever consists of a rigid arm or bar pivoted or bearing on a point called the fulcrum and has a weight arm and a power arm.
LOCK NUT – A type of nut that is prevented from loosening under vibration. The locking action is accomplished by squeezing, gripping or jamming against the bolt threads.
LOOSE PULLEY – A pulley which turns freely on a shaft so that a belt can be shifted from the driving pulley to the loose pulley in order to stop a machine driven by an overhead belt drive.
LAND – The top surface of a tooth of cutting tools, such as taps, reamers and milling cutters.
LEAD ANGLE – The angle of the helix of a screw thread or worm thread. It is the measure of the inclination of a screw thread from a plane perpendicular to the axis of the screw.
LEAD HOLE – A small hole drilled in a workpiece to reduce the feed pressure, aid in obtaining greater accuracy, and guide a large drill. Sometimes called PILOT HOLE.
LEAD OF THREAD – On a single threaded screw, the distance the screw or nut advances in one complete revolution.
LEFT HAND SCREW – One that screws into the mating part or advances when turned to the left or counter clockwise.
LIMITS OF SIZE – The minimum and maximum sizes permissible for specific dimensions.
LINE – A tube, pipe or hose which is used as a conductor of fluid.
LINKAGE – A movable connection between two units.
LOBE – The projecting part such as rotor lobe or the cam lobe.
LOCK NUT – A type of nut that is prevented from loosening under vibration.
The locking action is accomplished by squeezing, gripping or jamming against the bolt threads.
LOOSE PULLEY – A pulley which turns freely on a shaft so that a belt can be shifted from the driving pulley to the loose pulley in order to stop a machine driven by an overhead belt drive.
LEVER – A simple machine for obtaining mechanical advantage. The lever consists of a rigid arm or bar pivoted or bearing on a point called the fulcrum and has a weight arm and a power arm.
LINCOLN MILLER – One of the manufacturing type milling machines, all of which are characterized by the fixed table height with vertical adjustment of the spindle, in contrast with the column and knee type in which the work table is vertically adjustable.
LINISHING MACHINE – Automatic mirror polishing machine capable of polishing one or more parts at a time on the same polishing band or disc.
LIQUID COOLED ENGINE – An engine that is cooled by the circulation of liquid coolant around the cylinders.
LUMSDEN GRINDER – Oscillating type of grinding machine. The tool to be ground is secured in a chuck having a range of adjustments such that any desired angle can be ground.
LANG LAY ROPE – A rope in which the wires are twisted in the same direction as the strands are.
LEFT HAND LAY ROPES – Ropes in which the strands bend round to the left.
LEVEL LUFFING – Luffing mechanism which ensures that the crane hook travels along an almost horizontal path when luffing is in progress.
LIFT – Hoisting equipment adapted to lift loads vertically.
LIFTING CAPACITY – The maximum safe load the machine is designed to handle.
LIFTING MAGNET – Handling device, operating on direct current. Widely used in handling steel and cast iron loads.
LIFTING TACKLE – A system of stationary and movable sheaves interlinked by a pliable member in the form of a wire rope to obtain a gain in either force (power lifting tackle) or speed (speed lifting tackle).
LUFFING or DERRICKING – It is the pivoting of the crane jib in a vertical plane so as to change the reach.
LATTICE, SPACE – The term that is used to denote a regular array of points in space. For example, the sites of atoms in a crystal. The points of the three dimensional space lattice are constructed by the repeated application of the basic translations that carry a unit cell into its neighbour.
LIQUIDUS – The temperature at which freezing begins during cooling and ends during heating under equilibrium conditions, represented by a line on a two phase diagram.
LANCING – A special form of piercing in which the entire contour is not cut, the blanked material remaining as a tab.
LAPPING – Finishing process following grinding, and designed to produce an exceptionally high degree of surface finish as well as a perfectly true surface accurate to size within extremely close limits, by using very fine abrasives.
LIMITS OF ACCURACY – Under a limit system, the workman aims at producing a component, the acceptable size of which may fall between two limits of size.
LINEAR ACCELERATION – The time rate of change of liner velocity.
LINEAR VELOCITY – The time rate of change of linear displacement of a point or body.
LINK – Name given to anybody which has relative motion to another. Also called ELEMENT. A RIGID LINK is one whose deformations are so small that they can be neglected in determining the motions of various other links in a machine. A belt or chain is a FLEXIBLE LINK.
LOWER PAIRS – Types of kinematic pairs, namely two elements have surface contact and when relative motion takes place, the surface of one element slides over the surface of the other element.
LATENT HEAT – Heat energy which causes a change of state without any change of temperature.
LIMITING CONTROLS – Safety controls.
LIQUID LINE CHARGING VALVE – Used for high side charging.
LIQUID LINE SHUT OFF VALVE – Manual valve installed in liquid line near condenser well to shut off flow of refrigerant between the condenser and the liquid line.
LIQUID NITROGEN SHIELD – At room temperature, it can absorb any heat leakage from outside and reduce temperature between itself and cryogenic refrigerant surrounding the cable.
LIQUID NITROGEN SYSTEM – A non-mechanical refrigeration system for transport use.
LITHIUM BROMIDE – Used in combination with water in absorption cooling systems.
LOW PRESSURE CONTROL – An electric switch responsive to pressure, connected into the low pressure part of a refrigeration system. Usually closes at high and opens at low pressure.
LOW PRESSURE CUTOFF SWITCH – Senses system pressure only, wired in series with the magnetic clutch.
LOW SIDE FLOAT – Metering system which locates a float in the low pressure side of the refrigeration system.
LOW TEMPERATURE TRANSPORT – Refrigerated trucks that maintain temperatures in the range of 0°C and below.
LEAN MIXTURE – An air fuel mixture that has a relatively high proportion of air and a low proportion of fuel.
LOW SPEED CIRCUIT – The circuit in the carburettor that supplies fuel to the air passing through the air horn during low speed, part throttle operation.
LIGAMENT – The metal between tube holes in boiler practise. Section of the metal not cut away between two adjacent tube holes.
LOCOMOTIVE BOILER – A specially designed boiler, specifically meant for self propelled traction vehicles on rails.
LOG SHEET – A forced reminder to check certain components of a boiler to prevent trouble from developing later and to note if proper operation is taking place. A data sheet.
LOW WATER CUT OFF – A device that shuts down the boiler immediately if the water drops to a dangerously low level.
LAP OF D SLIDE VALVE – It is that portion of the valve face which overlaps the ports when the valve is in its central or neutral position. The distance overlapping on the outside is called OUTSIDE LAP or
STEAM LAP, and the distance overlapping on the inside is called INSIDE LAP or EXHAUST LAP.
LAYBRINTH GLAND – A type of gland consisting of a series of intricate passages, labyrinths, which are designed to destroy the kinetic energy developed by the steam leaving through the small clearance space. In the clearance space, this energy is converted to thermal energy.
LEAD OF D SLIDE VALVE – The amount by which the steam port is opened by the valve when the piston in a steam engine cylinder is at the begining of its stroke.
LOW PRESSURE TURBINE – A turbine operating at approximately atmospheric pressure and expanding to condenser pressure.
LATENT HEAT – The quantity of heat required to change the state or condition under which a substance exists without changing its temperature.
LATENT HEAT OF FUSION – The amount of heat which must be added to one kilogram of material to change its state from a solid to a liquid or which must be subtracted from one kilogram of a liquid to change it to a solid.
LATENT HEAT (internal) – The amount of heat that the water will absorb (latent heat minus heat equivalent of work of evaporation), at the boiling point without a change in temperature.
LATENT HEAT OF VAPOURIZATION – Amount of heat to be added to (or subtracted from) one kilogram of the refrigerant to cause it to vaporize (or condense). Also, the amount of heat energy in a gas which is in addition to that found in the liquid at the same temperature.
LAW OF CONSERVATION OF ENERGY – States that energy can neither be created nor destroyed. However, it can be stored in various forms and can be transferred from one form to another. In other words, the total energy of a body or substance always remains constant.
LIQUIDS – are substances in which the molecules are loosely bounded. A definite volume is maintained by the bond forces, but can change the shape according to the shape of the container.
LACING – The positioning of spokes in the hub and rim of a wheel.
LATERAL RUNOUT – Side to side movement (wobble) of a wheel rim.
LAY SHAFT – Second shaft in a direct drive gearbox. It transmits power from input shaft to high gear pinion.
LOAD RANGE – Indicates the number of plies at which a tyre is rated, load range B equals 4 ply rating, C equals 6 ply rating, and D equals 8 ply rating.
LONG TRAVEL SUSPENSION – Suspension used on current competition dirt bikes to provide more than 150 mm of travel.
LAP JOINT – A joint formed between two overlapping members in parallel planes.
LASER BEAM CUTTING – Process that severs materials by melting or vaporizing them with the heat obtained from a laser beam, with or without the application of gas jets to augment the removal of material.
LASER BEAM WELDING – Process that produces coalescence of materials with the heat obtained from the application of a concentrated coherent light beam impinging upon the joint.
LIGHTLY COATED ELECTRODE – A filler metal electrode consisting of a metal wire with light coating applied subsequent to the drawing operation, primarily for stabilizing the arc.