Mechanical Engineering MACHINES & DEVICES Terms and Definitions | Terminology | Meanings

Mechanical Engineering MACHINES & DEVICES Terms and Definitions :-

ACCURATE – Without error within tolerances allowed, precise, correct, confirming exactly to standard.

ACHME THREAD – A screw thread having an included angle of 29° and largely used for feed screws on machine tools.

ACUTE ANGLE – An angle which is less than a right angle i.e. 90°

ADDENDUM – The portion of the tooth of a gear that extends from the pitch line to the outside.

ALIGN – To bring two or more components of a unit into correct positions with respect to one another.

ALLOWANCE – The intentional or desired difference between the maximum limits of mating parts to provide a certain class of fit.

ANGLE – The amount of opening or divergence between two straight lines that meet at a vertex or that intersect each other.

ANGLE OF THREAD – The included angle between the sides forming the groove of the screw thread

ANNULUS – A figure bounded by concentric circles or cylinders (e.g., a washer, ring, sleeve etc.).

ARC – A circular section of the circumference of a circle bounded by two equal radii.

ASSEMBLY – A unit that contains the parts that make up a mechanism or a machine.

AXIS – The line real or imaginary, which passes through the center of a body and about which the body would rotate if set revolving.

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.

ACCELERATING PUMP – A small cylinder and piston fitted to some types of SI engine carburettor, and connected to the throttle so as to provide a momentarily enriched mixture when the engine is accelerated.

ACCUMULATOR – A device used for storing liquid under pressure (sometimes used to smooth out pressure surges in a hydraulic system).

ACTUATOR – A device which uses fluid power to produce mechanical force and motion.

AFTER COOLER – A device used on the turbocharged engines to cool the air which has undergone compression.

AIR COMPRESSOR – A device used to increase air pressure.

AIR COOLED ENGINE – An engine that is cooled by the passage of air around the cylinders, not by passage of a liquid through water jackets.

AIR CONDITIONER – A device used to control the temperature, humidity, cleanliness and movement of air inside a room or a car.

AIR HAMMER – Power hammer, used for roughening out heavy forgings in foundry work.

ALTERNATOR – A electrical generator that produces alternating current (flow of current is considered to change in direction with each half cycle).

ARBOR PRESS – A hand operated machine capable of applying high pressure for the purpose of pressing parts together or removing parts.

AUTOMATIC LATHE – Specialized development from capstan and turret lathes, with a full automatic cycle of turning, boring and drilling of the workpiece, the function of the operator consists of loading or taking finished work from the machine.

AUTOMATIC SCREW MACHINE – Fully automatic single spindle or multiple spindle bar stock turret lathe.

AUTOMATIC WELDING MACHINE – Machine designed to carry out high speed electric arc or resistance welding in mass production processes, combining rapid production with accurate control of temperature.

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.

CAM – A plate or cylinder which transmits variable motion to a part of a machine by means of a follower.

CAP SCREW – A finished screw 5mm or larger, used for fastening two pieces together by passing the screw through a clearance hole in one part and screwing in into a tapped hole in the other.

CENTER – A fixed point about which the radius of a circle or an arc moves.

CENTER LINE – A line used on drawings to show the centers of objects and holes. The center line consists of alternate long and short dashes.

CHAMFER – To bevel or remove the sharp edge of a machined part.

CHECK VALVE – A valve which permits flow in one direction only.

CIRCULAR PITCH – The distance from the center of one gear tooth to the center of the next gear tooth measured on the pitch line.

CIRCUMFERENCE – A curved line forming a circle and the length of this line.

COIL SPRING – A spring steel wire wound in a spiral pattern.

COMMUTATOR – A number of copper bars connected to the armature windings but insulated from each other and from the armature.

CONVOLUTION – One full turn of screw.

CORE – The central or innermost part of an object.

COUNTER BORING – The operation of enlarging a portion of a hole for part of its depth and to a given diameter, as for the head of a fillister head screw.

COUNTER SINK – To cut or shape a depression in an object so that the head of a screw may set flush or below the surface.

CREST CLEARANCE – Defined on a screw form as the space between the top of a thread and the root of its mating thread.

CREST OF SCREW THREAD – The top surface joining the two sides of flanks of a thread.

CROWNED – A slight curve in a surface e.g., on a roller or race way.

CAPSTAN LATHE – Lathe designed to use a number of cutting tools mounted on a rotating turret or capstan, and arranged to perform turning operations successively.

CENTRE LATHE – Machine for carrying out turning, boring, and screw cutting operations on a work held between centers or in a chuck, but not for repetition work.

CENTRIFUGAL GOVERNOR – A governor which uses fly weight force to sense speed in order to control the fuel supplied to the combustion chambers.

CENTRIFUGAL PUMP – A pump using the centrifugal force produced by a rapidly rotating impeller to displace liquid.

CENTRIFUGE – A device with a rapidly rotating bowl which separates the impurities of a fluid by intense centrifugal force.

CIRCUIT BREAKER (lighting system) – A device that opens the circuit when the current draw becomes excessive and closes when the current flow is reduced.

CIRCULATING PUMP – The term applied to cooling water/ lubricating oil pumps which effect circulation of fluid.

COMPRESSOR – A mechanical device to pump air, and thereby increase the pressure.

CONDENSER (electrical) – An arrangement of insulated conductors and dielectrics for the accumulation of an electric charge.

CUPOLA – Special type of blast furnace, chiefly used for the melting of cast iron.

CYLINDRICAL GRINDER – Grinding machine designed to true up and bring to size cylindrical parts such as shafts, spindles, rollers etc.

DEDENDUM – The depth of a gear tooth space below the pitch line or circle. Also, the radial distance between the pitch circle and the root circle, which also includes the clearance.

DIAPHRAGM – A flexible dividing partition separating two compartments.

DOUBLE FLARE – A flared end of the tubing having two wall thicknesses.

DOWEL – A pin, usually of circular shape like a cylinder, used to pin or fasten something in position temporarily or permanently.

DRIFT PIN – A round tapered steel pin used to align rivet holes so that the rivet will pass through the holes easily.

DIESEL ENGINE – An internal combustion engine having fuel injected into the combustion chamber near the end of the compression stroke. The fuel is ignited by the heat of compression only.

DIODE – A device that allows current to pass but only in one direction.

DISC GRINDER – Grinding machine embodying one or more abrasive discs mounted horizontally on a vertical spindle, the work reposing on the surface of a flat rotating carrier or table.

DRAWCUT SHAPER – Type of machine with a traverse tool movement. In this, the work is fixed to the table which reciprocates under the tool, the tool moving across the table for the purpose of obtaining the feed.

DRILL GRINDER – Machine employed for the accurate grinding of the cutting points and lips of twist drills.

DRILL PRESS – A fixed machine to drive a tool in rotary motion.

DRILLING MACHINE – Machine tool used for the production of holes with a drill, fall under two classes—bench drilling machine and the pillar drilling or upright drilling machine.

DROP STAMP – Machine for producing drop stampings and forgings, may be free falling type or controlled falling type.

DRY CELL (dry battery) – A battery that uses no liquid electrolyte.

DUPLEX MILLER – Manufacturing type milling machine sometimes called a duplex head miller, has two head stocks supporting two opposed spindles. This enables two face mills or two horizontal cutters, to work simultaneously on opposite sides of the workpiece.

DYNAMOMETER – A device for absorbing the power output of an engine and measuring torque or horse power, so that it can be computed into brake horsepower.

ELECTRIC DRILL – Hand operated, portable drilling machine driven by electric power.

ENGINE – A machine that converts heat energy into mechanical energy. The assembly that burns fuel to produce power is sometimes called POWER PLANT.

ECCENTRIC – A circle or cylinder having a different center from another coinciding circle or cylinder. Also, a device for converting rotary motion to reciprocating motion.

END PLAY – As applied to a shaft, the amount that the shaft can move backward and forward.

EYE BOLT – A bolt threaded at one end and bent to a loop at the other end.

FEATHER – A sliding key, sometimes called splint. Used to prevent a pulley, gear or other part from turning on a shaft but allows it to move lengthwise. The feather is usually fastened to the sliding piece.

FILLET – A concave surface connecting the two surfaces meeting at an angle.

FLANGE – A metal part which is spread out like a rim, the action of working a piece or part to spread out.

FLANK (Side of thread) – The straight part of the thread which connects the crest with the root.

FLARE – To open or spread outwardly.

FULCRUM – The pivot point of a lever.

FLUSH – When the surfaces of different parts are on the same level, they are said to be flush.

FLUTE – A straight or helical groove of angular or radial form machined in a cutting tool to provide cutting edges and to permit chips to escape and the cutting fluid to reach the cutting edges.

FIXED DISPLACEMENT PUMP – A type of pump in which the volume of fluid handled per cycle cannot be varied.

FINE BORING MACHINE – Machine used for boring to very close limits, the holes in pistons, the bores in cylinder blocks, the bearings in motor car and aero engine connecting rods, valves as fitted to steam and other piping, may have a horizontal or vertical spindle.

FLY BALL GOVERNOR – Conventional type of centrifugal governor, commonly called a mechanical governor.

FORGING MACHINE – Machine designed to shape a metal article while the material is in the hot plastic state by applying the necessary force or pressure.

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.

HAND WHEEL – Any of the various wheels found on machine tools for moving or positioning parts of the machine by hand feed, as the tailstock handwheel on a lathe.

HALF MOON KEY – A fastening device in a shape somewhat similar to a semicircle.

HELICAL GEAR – A gear in which the teeth are cut at some angle other than a right angle across the gear face.

HELICOIL – A thread insert used to repair worn or damaged threads. It is installed in a retapped hole to bring the screw thread down to original size.

HELIX – The curve formed by a line drawn or wrapped around a cylinder which advances uniformly along the axis for each revolution, as the thread on a screw or the flute on a twist drill. A helix is often called a spiral in the shop.

HELIX ANGLE OF A THREAD – The angle made by the helix of the thread at the pitch diameter line with a line at right angle to the axis.

HEXAGONAL NUT – A nut having six sides and shaped like a hexagon.

HEAT EXCHANGER – A device used to cool a fluid by transferring heat.

HOIST – Appliance or machine for lifting heavy material, also called lifting tackle.

HYDRAULIC GOVERNOR – A governor using fluid to operate the fuel control.

INVOLUTE GEAR TOOTH – A curved tooth generated by unwinding a string from a cylinder to form the curve.

INTERCOOLER – Heat exchanger for cooling the air between the stages of compression.

INTERNAL COMBUSTION ENGINE – An engine that burns fuel within the cylinder itself as a means of developing power.

INTERNAL GRINDER – Machine used to finish internal surfaces such as engine cylinders, ball bearing races, and similar work that require excellent accuracy and high finish.

JOURNAL – The part of a shaft or axle that has been machined or finished to fit into a bearing.

JIG BORING MACHINE – An extremely accurate machine tool having a precession spindle and a table to hold the work. The table and spindle are movable with built in measuring devices. Used for spacing and producing precision holes in tools, dies, and small lot production where extreme accuracy is required.

KEYS – Metal pieces of various designs that fit into a slot in a shaft and project above the shaft to fit into a mating slot in the center hole of a gear or pulley to provide a positive drive between the shaft and the gear or pulley.

KEYSEAT – The slot or recessed groove either in the shaft or gear, which is made to receive the key. Also, it is called a KEYWAY.

KNURL – A uniform roughened or checked surface of either a diamond, a straight or other pattern.

KNUCKLE PRESS – Press designed to exert a great pressure. It is a strong, heavily built and a rather slow-moving machine, and the standard range varies from 60-100 tons per sq. inch.

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.

MACHINE – A mechanical device, mechanism, or apparatus which transmits power and motion to perform work.

MACHINE TOOL – Type of power driven machine for cutting metal as employed in machine shops, the term being usually restricted to those which use the tool that produces waste material in the form of chips or cuttings. Typical machine tools are lathes, planers, shapers, slotters, borers, drills, broaches, millers and saws.

MAJOR DIAMETER – On a straight thread, the diameter of the imaginary cylinder that just touches the crest of an external thread or the root of an internal thread.

MALE PART – The external part of any workpiece which fits into a hole, slot or groove of the mating part.
MANUAL VALVE – A valve which is opened or closed or adjusted by hand.

MESH – Engaging one part with another, as the teeth of one gear mesh with the teeth of a mating gear.

MICRON – One millionth of a meter or 0.039370 inch.

MINOR DIAMETER – On a straight thread, the diameter of the imaginary cylinder which just touches the root of an external thread or the crest of an internal thread.

MORSE TAPER – A self holding, standard taper largely used on drilling tools, drilling machine spindles, and some lathes.

MULTIPLE THREADED SCREW – A screw with two or more threads cut around the periphery of the workpiece to provide an increased lead with a specified pitch.

MANDREL PRESS – Press for the purpose of fitting mandrels to the bore of the work.

MICHIGAN GEAR SHAPER – Machine incorporating a number of shaped cutters, used to produce all the teeth on spur or helical gears simultaneously.

MILLING MACHINE – Machine tool designed to remove metal from the surface so as to size and shape it by means of a revolving multiple toothed cutter called milling cutter.

MOTOR – A rotating electromagnetic device used to convert electrical energy into mechanical energy.

MOTOR VEHICLE – Any type of self propelled vehicle mounted on wheels or tracks.

MOULDING MACHINE – Mechanical device for making moulds at a much faster rate.

MULTIPLE SPINDLE DRILLING MACHINE – Machine used for drilling a large number of holes in one operation, built purely for repetition work.

MULTIPLE SPINDLE LATHE – Machine, generally of the automatic type, with up to six spindles mounted in a drum, this indexes in sequence, so that a different operation is performed at each station, and one revolution of the drum completes a piece of work.

NUT – A metal fastener of square, hexagon or other shape, having an internal
thread which screws onto a bolt, stud or arbor.

NIBBLER – Machine designed to cut metals in sheet form to any required shape. The machine comprises a small punch moving up and down at high speed, and so taking a considerable number of small nibbles or cuts.

NUT TAPPING MACHINE – Device for tapping, that is providing the screw threads on nuts.

OIL COOLER – A heat exchanger for lowering the temperature of oil.

OIL PUMP – Mechanical device to pump oil (under pressure) into the various oil galleries.

OPTICAL COMPARATOR – A machine that enlarges the profile view of a part and compares it to a standard profile.

OSCILLOSCOPE – A device for recording wave forms on a fluorescent screen, proportional to the input voltage.

OVER RUNNING CLUTCH – A clutch mechanism that transmits power in one direction only.

OVER SPEED GOVERNOR – A governor that shuts off the fuel or stops the engine, only when excessive speed is reached.

OFF CENTER – Not on the true center line or axis, offset, eccentric or inaccurate.

PEEN – The end of the head of a hammer opposite the face, such as ball, straight or cross peen, and used for peening or riveting.

PILOT – A guide at the end of the counter bore which fits freely into the drilled hole and align the body of the counterbore while cutting takes place.

PILOT SHAFT – A shaft positioned in or through a hole of a component as a means of aligning the components.

PILOT VALVE – A valve used to control the operation of another valve.

PINION – The smaller of the pair of gears regardless of the size or type.

PIPE THREAD – A 60° thread having flattened crest and roots which are cut on a taper. Pipe thread is used on piping and tubing.

PITCH – In screw threads, the distance from a point on one thread to a corresponding point on the next thread measured parallel to the axis. In the case of spur gears, indicates the size of the gear teeth and is correctly called diametral pitch.

PITCH DIAMETER – For screw threads, the diameter of an imaginary cylinder, the surface of which would pass through the threads at such points that would make the width of the groove and width of the land equal to one half the pitch.

PLAY – The movement between two components.

PULLEY – A wheel having a plain or V groove rim over which a belt runs for the transmission of power from one shaft to another.

PLAIN MILLER – Milling machine in which milling can be carried out in a direction parallel with the axis of the arbor or at right angles to it , but no swivelling of the worktable is possible.

PLANING MACHINE – Machine for removing material from plane surfaces by means of cutting tools fixed in the machine. It comprises a bed, a travelling worktable on which the parts to be planed are carried, standards, a cross slide, tool box and gearing. Also called PLANER.

PLANOMILLER – Milling machine, sometimes called a slab miller, similar in shape and appearance to a planing machine, but having cutter hands instead of clapper type tool boxes.

PLUNGER PUMP – A pump which operates and displaces fluid by means of a plunger.

PNEUMATIC TOOL – Design of hand tool operated by air pressure e.g., pneumatic drill, pneumatic hammer or riveter.

POWER HAMMER – Machine for shaping metal while hot, grouped into three classes, according to the power supplied: compressed air, steam or hydraulic pressure.

POWER PLANT – The engine or power producing mechanism.

PRESS – Machine designed to manipulate sheet and strip metal so as to produce a given shape or form.

PROFILING MACHINE – Form of milling machine designed to produce delicate parts whose form or contour is irregular, particularly for mass production by the use of jigs and so on, of small machine and other parts, or where the production of interchangeable parts is desired.

PRONY BRAKE – A friction brake used for engine testing.

PUMP – Mechanical device in which a fluid, gas or liquid, is lifted or forced against an external pressure, main types are reciprocating or piston pumps, centrifugal pumps and rotary displacement pumps.

PUNCHING MACHINE – Machine designed to cut metal blanks from the sheet. It may be of the crank or eccentric variety; the frame of the C or double sided type. Also called PUNCH PRESS.

QUILL – A hollow shaft that revolves on a solid shaft carrying pulleys, gears or clutches. When the clutch is closed, the quill and shaft revolve together.

RACK – A straight metal strip having teeth that mesh with those of a gear to convert rotary into reciprocating motion or just the opposite.

RATCHET – A gear with triangular shaped teeth to be engaged by a pawl which gives it intermittent motion or locks it against backward movement.

RECESS – A groove cut below the normal surface of a workpiece.

RIGHT HAND THREAD – A screw thread which advances into the mating part when turned clockwise or to the right.

RIVET – A one piece fastener consisting of a head and a body and used for fastening two or more pieces together by passing the body through a hole in each piece and then forming a second head on the body end. It cannot be removed except by taking off the head.

RADIAL DRILLING MACHINE – Machine with the drill head working on an arm which has a rotary movement in the horizontal plane. In this the drill spindle could be moved to the positions required instead of moving the work for each hole to be drilled.

RADIATOR – A heat exchanger in which cooling water gives up heat without coming into direct contact with air.

RAM (pump) – Hydraulic ram, also termed a water ram, by which water is raised by its own momentum from a lower to a higher level.

RECTIFIER – A device, made of a diode or series of diodes, used in a welding machine, for converting alternating current to direct current.

RELAY – An electromagnetic switch which utilizes variation in the strength of an electric circuit to effect the operation of another circuit.

RELIEF VALVE – An automatic valve which is held shut by a spring of correct strength. Excessive pressure opens the valve and releases some of the gas or liquid.

RELIEVING LATHE – Machine for backing off the teeth of milling cutters to facilitate machining of metals.

REVERBERATORY FURNACE – Furnace in which ore or metal is melted by contact with the flame, but is not in contact with the fuel.

RHEOSTAT – A device to regulate current flow by varying the resistance in the circuit.

RIGBY HAMMER – Steam hammer used for a wide range of forging work.

RIVETING MACHINE – Power operated machine used to form rivet heads. May be classified according to the method of operation hydraulic, pneumatic, or steam and the manner in which the rivet head is formed.

ROLLING MILL – Mill in which ingots, bars, blooms, billets etc., of steel or other metals, are rolled to reduce or alter their sections.

ROLL TURNERS LATHE – Special design of lathe adapted for machining rolls employed for printing machines, calendars or rolling mills.

ROOTS BLOWER – An air pump or blower similar in principle to a gear type pump.

ROTARY BLOWER – Pump or compressor used to supply air or gas to a furnace, forge, internal combustion engine or similar application. This may be a vane, geared rotor, centrifugal or turbine type depending on the particular application and the volume of air or gas or the pressure required.

ROTARY PUMP – Pump used for liquid or gas, in which a rotating impeller is used, may be vane type, gear type centrifugal and turbine type.

SALT BATH FURNACE – Liquid bath furnace used for case hardening and heat treating of metals and alloys.

SAWING MACHINE – Machine tool for cutting metal by the use of a blade band, or disc provided with cutting teeth.

SCAVENGING PUMP – A piston type of pump delivering scavenging air to an engine.

SCRAP CUTTER – A type of double action press having a side ram whose purpose is to cut the scrap metal into short lengths in order to facilitate handling.

SCREW MACHINE – A power driven automatically controlled machine tool designed to produce finished parts from bar stock. Cams control the movement of the cutting tools, attachments and stock feeding devices to complete work pieces automatically at high production rates.

SENSITIVE DRILLING MACHINE – Type of machine in which drills are used with a sensitive hand pressure action.

SHAPING MACHINE – Type of machine used for the production of flat or curved surfaces. In this the ram which carries the tool reciprocates while the worktable which carries the workpiece moves perpendicular to the ram movement. Also called SHAPER.

SHEARING MACHINE – Machine designed for cutting sheet metal. It comprises a fixed blade and a shearing tool or blade.

SILENCER – A device for reducing the noise of intake or exhaust in an engine.

SLOTTING MACHINE – Machine whose mechanical principles are much the same as those of the shaping machine, but with the difference that the ram on which the slotting tool is mounted moves vertically, as in a vertical shaping machine. Also called SLOTTER.

SOLENOID – An electrically operated magnetic device used to do work.

SPOT WELDING MACHINE – Fixture in which sheets of metal to be welded together are clamped between two electrodes through which an electric current is passed.

SUPERCHARGER – An air pump driven by an engine, which fills the cylinders with air at a higher pressure than atmospheric pressure.

SURFACE GRINDER – It is a general purpose machine tool used to finish machine a plane surface. There are two types—horizontal and vertical.

SCREW – A helix formed or cut on a cylindrical surface which may advance along the axis to the right or left. The helix may be single or multiple.

SCREW THREAD – A ridge of uniform section or shape in the form of a helix on the external or internal surface of a cylinder, or in the form of a conical spiral on the external or internal surface of a cone.

SET SCREW – Usually a hardened steel screw having either no head or a square head and with various degrees of points or ends to lock or tighten adjustable machine parts in position on a shaft.

SHOULDER SCREW – A screw having two or more diameters or shoulders and commonly used for supporting levers and other machine parts that have to operate freely.

SINGLE THREAD – A screw thread cut around a cylinder having a single start in which the lead is equal to the pitch.

SOCKET HEAD – Screw head having a hexagonal or other form of recessed socket in the head so that the screw can be turned with a wrench or key, as a hexagon key.

SPLINE – Slot or groove cut in a shaft or bore, a splined shaft onto which a hub, wheel, gear etc. with matching splines in its bore is assembled so that the two must turn together.

SPOOL VALVE – A hydraulic directional control valve in which the direction of the fluid is controlled by the means of a grooved cylindrical shaft (spool).

SPRING – An elastic device which yields under stress or pressure but returns to its original state or position when the stress or pressure is removed.

SPUR GEAR – A toothed wheel having external radial teeth.

SQUARE THREAD – A form of screw thread in which the cross–section of the thread forms a square, making the width of the thread equal to the space between the threads.

STEP BLOCK – A block of steel or cast iron having a series of steps and used for supporting the ends of machine clamps when clamping work to the table.

STOPS – Devices attached to the movable parts of a machine tool to limit the amount of travel.

STUD – A rod having thread on both ends.

STUFFING BOX – A chamber having manual adjustment device for sealing.

TAPER – A shaft or hole that gets gradually smaller toward one end.

TAPER PINS – Steel pins used for locating and holding the machine parts in position on a shaft.

T-BOLT – A threaded bolt having a square or rectangular end which fits into the T slot of a machine table for clamping workpieces.

TEMPLATE – A flat pattern or guide plate usually made from sheet metal and used as a gauge or guide when laying out, drilling, forming in a machine or filing irregular shapes on metal pieces.

THUMB SCREW – A type of screw having a winged or knurled head for turning by hand when a quick and light clamping effect is desired.

TOLERANCE – A fractional allowance for variation from the specifications.

T-SLOT – A recessed or undercut slot made with a special T shaped cutter in the tables of machine tools to receive the square head of a T bolt for clamping workpiece.

TAPE CONTROLLED MACHINES – Machines which have partial automation in which the movements of a machine tool and cutters are automatically controlled by a magnetic tape or cards which have been punched to indicate data previously planned for the sequence of each operation to be performed.

TAPPING MACHINE – Machine designed to cut threads in holes in nuts and other parts.

TESTING MACHINE – Machine designed to apply accurately measured loads to a test piece and, in many cases, to measure the resulting extension, compression or deflection, in order to ascertain the physical properties of materials.

THYRISTOR – A type of semiconductor device that acts as a switch. It turns on when a certain voltage is applied to the gate, and it turns off when the current flowing between the other two terminals stops or reverses.

TOOL GRINDER – Special machine for the grinding of turning, planing and other tools.

THREAD MILLER – A machine that cuts threads by using a rotating milling cutter.

TROCHOID PUMP – An oil pump consisting primarily of a pair of rotors of special shape.

TURBO CHARGER – An exhaust gas driven turbine directly coupled to a compressor wheel.

TURRET LATHE – Machine generally larger than a capstan lathe, but using similar tools. The main difference between them is that the turret saddle has longitudinal movement on the guides of the bed.

UNIVERSAL GRINDER – Type of grinding machine having a wide range of application and specially suited to work that has to be ground at an unusual angle. Provided with a swivel table and headstock and a wheel head that can be rotated on its base.

UNIVERSAL MILLING MACHINE – Design of milling machine of the column and knee type, roughly similar in general design to plain milling machine (column and knee type), but usually of less robust construction and having additional features that widen its field of usefulness e.g., a worktable that swivels in a horizontal plane so that it is not restricted to two right angled motions.

U-BOLT – An externally threaded fastener bent in the shape of the letter U and with both ends threaded.

VALVE – Any device or arrangement used to open or close an opening to permit or restrict the flow of a liquid, gas or vapour.
V-BLOCKS – Square or rectangular shaped blocks of steel that are usually hardened and accurately ground. These have 90° V groove through the center and are provided with clamps for holding round workpiece for laying out, drilling, milling etc.

VISE – A mechanical device of many designs and sizes in which work pieces are clamped for hand or machine operations.

V-WAYS – The top of the bed of a lathe, planer or other machine tool which acts as bearing surface for aligning and guiding the moving parts such as the carriage of a lathe.

VERTICAL MILLING MACHINE – Milling machine in which the cutter spindle rotates about a vertical axis (as on most drilling machines), but which in certain other respects has much in common with a plain miller.

VERTICAL TURRET LATHE – A lathe with a vertical spindle and ways that carries the work in a chuck and has cutting tools mounted in a five position turret and side heads.

VIBRATION DAMPER – A specially designed device mounted to the front of an engine crank-shaft to reduce torsional vibration.

WANKEL ENGINE – A rotary type engine in which a three lobe rotor turns eccentrically in an oval chamber and thus performs cycle of operations.

WATER BRAKE – A device for engine testing in which the power is dissipated by churning water.

WELDING MACHINE – Equipment used to perform the welding (joining) operation, for example, spot welding machine, arc welding machine, seam welding machine etc.

WORM – A threaded cylinder which meshes with and drives a worm gear, the thread being specially designed to mate with the teeth in the worm gear.

WORM GEARS – Gears with teeth cut at an angle to be driven by a worm.

The teeth are usually cut out with a hob to fit the worm.