Mechanical Engineering Dictionary-Mechanical Processes

Important Terms and their Meaning of Mechanical Engineering-Mechanical Processes:

AGING OF A PERMANENT MAGNET – It is the process of normal or accelerated change, under continued normal or specified artificial conditions, in the strength of the magnetic field maintained.

ARC WELDING – Method of welding or uniting two metallic pieces in which the metal is melted by the heat of an electric arc.

ATOMIC HYDROGEN WELDING – Welding of metallic pieces in which heat is liberated by hydrogen atoms when combining into molecules, is used to fuse the metal.

AUTOMATIC ARC WELDING – Method of arc welding in which the arc moves along the joint to be welded, feeds the electrodes to the arc, and governs the arc length, by automatic means.

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.

CALENDERING – A process that involves rolling of the product into sheets to achieve the desired surface finishes and thickness.

CASTING – Process of producing a metal object by pouring molten metal into a mould.

COINING (embossing) – Shaping a piece of a metal in a mould or die often creating raised figures or numbers.

COLD DRAWING – Reducing the cross section of a metal bar or rod by drawing it through a die, at a temperature below the recrystallisation range, usually room temperature.

COLD ROLLING – Reducing the cross-section of a metal bar in a rolling mill below the recrystallisation temperature, usually room temperature.

COLD SAWING – Any sawing process in which the chips are not heated to the softened state.

COLD WORKING – Deforming a metal plastically at a temperature below its lowest recrystallisation temperature. Strain hardening occurs as a result of this permanent deformation.

CONFINED FLOW – Confined flow is the basis of drop forging and hot pressing. In this, the metal is ultimately confined in all directions, being forced to behave as pasty fluid in filling every portion of the confining cavity.

CENTERLESS GRINDING – Method of grinding metallic parts in which the piece to be ground (circular piece) is supported on a work rest, and passed between a grinding wheel running at a high speed and a controlling wheel running at a slow speed.

CENTRIFUGING – Casting of molten metals by using centrifugal force instead of gravity. The mould (or moulds) is rotated about a centre where molten metal is poured and allowed to follow sprues outward and get into the mould cavity.

CENTRIFUGAL CASTINGS – Castings of cylindrical design are made by the introduction of molten metal into revolving permanent moulds, known as centrifugal casting machines, where the centrifugal force is employed to bring pressure in filling of the mould.

CLADDING – The joining of one metal (usually sheet or plate) to another by using heat and pressure or by an explosive force. With this method, a thin sheet of more expensive metal or one less likely to corrode may be applied to a less expensive metal or one more likely to corrode.

CLIMB MILLING – Milling process in which the work is fed in the same direction as the path of the teeth on the cutter, below the arbor.

COUNTER SINKING – It is the opening out of the ends of a hole to form a conical hollow for receiving the head of a countersunk screw, rivet or bolt.

CRIMPING – Producing flutes or corrugations. Often used to gather metal as for stovepipe joints.

CROWNING – Shaping of the rim of a belt pulley so that the diameter at the centre of the face is greater than at the edges so as to keep the belt on the crown of the pulley.

CUPPING – Process in which a flat blank is converted into a cup like form.

CUT OFF – An operation that shears a stamping from a strip or bar.

DEFORMATION – Alteration of the form or shape as a result of the plastic behaviour of a metal under stress.

DIECASTING – Casting metal into a metallic mould by using pressure instead of gravity or centrifugal force.

DIFFUSION – The process of atoms or other particles intermingling within a solution. In solids, it is a slow movement of atoms from areas of high concentration towards areas of low concentration. The process may be (a) migration of interstitial atoms such as carbon, (b) movement of vacancies or (c) direct exchange of atoms to neighbouring sites.

DINKING – Cutting of non-metallic articles from the sheet, usually involving such operations as blanking and piercing.

DRAW FILING – Finishing operation in filing during which the file is moved in the direction of the greater length of the work, being held like a spoke shave.

DRAWING – Process, in press work, which involves reducing the diameter or cross-sectional dimensions of a cup, shell, tube, bar or wire.
DRILLING – Power or hand operated method for the production of holes in metal or other solid materials with a drill.

DROP FORGING – Drop forging is the operation in which a metal part is formed by repeated hammer blows on a bar or billet placed between a pair of dies containing the impression of the finished shape desired.

EDGING – Edging is a gathering operation. Here the metal is displaced to the desired shape by striking it between two dies. As the dies strike, the stock, metal is gathered toward the center of the cavity and some sideways movement also takes place.

ELECTRON BEAM WELDING – The fusion of material by energy imparted from an intense beam of electrons.

ELECTROPLATING – Coating an object with a thin layer of metal through electrolytic deposition.

ELECTRIC RESISTANCE WELDING – Uniting the parts by heating them to welding temperatures and then forcing the ends together by mechanical pressure.

EMBOSSING – Operation of raising a design or form above the surface of a component by means of high pressure affected by pressing or squeezing action.

ETCHING – Process of marking a metal by eating into it with an acid or other chemical.

EXFOLIATION – Cracking of the outer skin of the metal.

EXTRUSION – Process in which metal (often heated) is caused to flow through a restricted orifice by using an extremely high force, so creating an extremely elongated strip of uniform, but comparatively small cross-section.

FELLOWS PROCESS – Method of generating involute gear teeth by the use of pinion shaped cutter.

FETTLING – Operation of removing any sand left on the casting from the mould and core, and also the removal of surplus metal that is always associated with castings direct from the foundry, such as runners, risers, feeders and so on.

FILAMENT WINDING – A composite manufacturing process where the end product is to have a hollow internal shape. A filament of the fibre is wound around a form, then bonded in place with the resin matrix.

FILE CUTTING – Incising the teeth on a file blank by means of a mechanically driven chisel of high speed steel.

FILING – Operation of smoothing a rough surface or reducing the thickness of a piece of material with a file.

FITTING – Finishing of mating parts to dimensions which will allow the desired tightness or freedom of movement on assembly.

FLANGING – any process producing a flange. A flange may draw on a shell or a tube.

FLASH WELDING – Method of electric resistance welding of sections of material by the formation of an electric arc between the edges of the pieces to be joined and then pressing together with a light pressure the molten edges.

FLATTING – Finishing operation carried out at the end of the work cycle to remove the various hammer marks on the surface left in by the previous shaping operations.

FLOAT GLASS – A glass manufacturing process that produces a continuous sheet or ribbon of glass.

FORGING – A method of metal working in which the metal is hammered into the desired shape, or is forced into a mould by pressure or hammering, usually after being heated to a more plastic state. Hot forging requires less force to form a shape than that of cold forging, which is usually done at room temperature.

FORM GRINDING – Grinding of tool designed for machining and other operations, in such a way that they are provided with the precise form required for their work, or regrinding them to restore the form after it has been lost as a result of service.

FORMING – Production of shaped part either by means of feeding in a tool ground to shape or form of the part or by what is known as spinning.

FOUNDRY – Place where metal is melted and poured into required shapes.

FULL AUTOMATIC – Process in which all phases, once started, are accomplished without the need of further manual input.

FULLERING – Similar to drawing and is a preliminary forging operation which results in an elongated section between two heavier sections.

FUSION – Merging of two materials while in a molten state.

FUSION SAWING – Sawing material in the cold state by means of friction discs, where a quick and rough cut is sufficient for the purpose.

FUSION WELDING – Welding process in which the metals are brought to the temperature at which they melt, and are joined without hammering.

GALVANIZING – The application of a layer of zinc to the surface of iron and steel for protection from corrosion.
GAS WELDING – Method of fusion welding in which a flame produced by the combustion of gases is employed to melt the metal.

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

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

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

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

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

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

HAMMER WELDING – Uniting by heating two pieces of mild steel or wrought iron to a soft malleable condition and hammering them together on an anvil.

HEADING – A metal gathering or upsetting operation. Originally used for production of screw and rivet heads in cold working process.

HONING – Process whereby a mirror finish is given to important bearing surfaces by using hones or abrasive tools that normally employ both rotary and longitudinal motion.

HOOKER PROCESS – It is usually a cold extrusion process and is commonly employed for the production of small, thin walled copper and aluminium seamless tubes and small cartridge cases.

HOT PRESSING – Forming or forging tough metals such as alloy steel at high temperatures.

HOT PRESSURE WELDING – In this, bonding of two materials is brought about by application of high pressure and production of mutual deformation at temperatures below the melting range of either. Bonding results from interlocking of the atoms of each piece with some additional interlocking introduced by diffusion.

HOT ROLLING – A process of forming metals between rolls in which the metals are heated to temperatures above the transformation range.

HYDROJET – A manufacturing process in which a material is cut by a high pressure jet of water often containing an abrasive material to enhance cutting action.

IMPACT EXTRUSION – In this process, a slug of metal is placed on a solid bottom die, and the impact of the punch causes the metal to flow back over the punch, which has a uniform section, slightly relieved.

INDEXING – Rotation of a workpiece by small uniform amounts, with or without the aid of change wheels, mainly in connection with milling operation.

INTERNAL GRINDING – Mechanical grinding of the internal bores of gears, bushes and wide variety of machine parts and articles of specialized character.

JOGGLING – Bending operation necessary for making a lap joint, yet keeping the top surface flush.

KNURLING – A cold working process in which a series of sharp serrations on a hardened steel roller are pressed into the material being knurled.

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.

MAAG PROCESS – The process combines precision grinding of the flanks of the gear teeth with a generating action which ensures that a correct involute form will be maintained, or restored if distortion has taken place as a result of hardening and heat treatment.

MACHINING – Machining is the art of using machine tools and cutting tools in combination to reduce a piece of material to some specified shape and dimensions.

METALLIZING – Process of spraying metal on to a metallic or non-metallic surface, for building up of worn parts and for the protection of components against corrosion.

MILLING – Operation in which a workpiece is given a specific shape or form by means of a rotating cutter having many cutting teeth.

MILL WRIGHTING – General maintenance, repair and the making of parts for machinery in a factory. A millwright is a craftsman in the true sense of the word.

MOULDING – Practise of making moulds in which to pour molten metal to form castings.

NOTCHING – Operation of cutting gaps on the edge of an article.

OPEN DIE FORGING or SMITH FORGING – A forging process in which a drop hammer delivers blows of great force to a heated metal that is shaped by manipulating it under the hammer.

OXY ACETYLENE CUTTING – A method of cutting heavy iron or steel plates with the aid of an oxyacetylene torch.

PEENING – Work hardening the surface of metal by hammering or blasting with shot (small steel balls). Peening introduces compressive stresses on weld surfaces that tend to counteract unwanted tensile stresses.

PERFORATING – Piercing many small holes close together.

PICKLING – Process of cleaning (that is removing oxide film from) castings by dipping them into an acid bath prior to plating, painting or further cold working.

PIERCING – Producing holes in a blank by driving a punching tool into the mass of the metal, while at the same time forcing the displaced material into the particular form required by the part, this is known as deep piercing.

PINNING – Scratching of the work surface during a filing operation caused by small particles of metal getting wedged in front of the teeth of the file.

PLANING – Producing flat or plane surface on a moving or other part by removing metal from them by means of a cutting tool used in a planning machine.

PLANISHING – Hammering operation by which the surface of a metal component is brought to a first class condition for such operations as polishing, plating and spraying.

PLATE MOULDING – Specialized form of moulding which consists of one or more patterns mounted on a plate with the runner and ingates being allowed for in the pattern.

PLATE EDGE PLANING – Smoothing and generally making true and accurate the edges of large plates.

PLATING – The process of depositing a layer of one metal on another, often done electrically, for the purpose of corrosion protection, appearance, improved electrical conductivity, and other engineering requirements.

POWDER METALLURGY – Forming parts out of powdered metal by compacting the powder into a mould under great pressure and heating it.

PRESSING (hot) – Process of shaping a metal article by pressure and while the metal is hot, and without any interstate forging.

PRESSURE WELDING – Method of uniting two sheets of metal by squeezing them between heated dies.

PROFILING – Method of milling irregular forms by reproducing the form of a master template, form or pattern.

PULTRUSION – A process that is opposite to extrusion and is used in composite part manufacturing.

PUNCHING – The operation of cutting a hole in sheet metal using a die. The whole material is scrapped. It is a shearing operation carried out in a press.

PUSH FIT – Class of fit which allows two parts to be assembled under hand pressure.

REFINING OF METAL – Process of removal of impurities from metals or alloys, resulting in improved properties or a different product. Also refers to the refining of the grain of a coarse grained metal or alloy.

REFLEX PROCESS – Photo printing process enabling copies to be made from opaque originals.

RESISTANCE WELDING – Uniting two pieces of metal by the passage of a heavy electrical current (high amperage current) while the surfaces are pressed together.

RIVETING – A hammering operation in which the end of a metal pin (i.e., a rod or rivet) is pressed over or spread out. It may be either a hot or cold working process.

ROLL FORMING – Process of passing strip stock between driven rollers that form the strip to the shape desired.

ROLL GRINDING – The operation of grinding large rolls of steel mills or calendars.

ROLL THREADING – A method of threading a part by pressing and rolling between serrated dies.

RUBBER METAL BONDING – Bonding of natural rubber or synthetic rubber to metal surfaces.

RUNNING FIT – Term used of parts which are assembled so that they are free to rotate a type of clearance fit.

SAND BLASTING – Process used for cleaning metal surfaces, consists of directing a stream of air under pressure, into which quartz sand is introduced as an abrasive, on to the work.

SCREW CUTTING – Process of cutting a screw thread, usually in a lathe, which involves copying a master screw called the leading or lead screw in the nature of its pitch, but not its profile.

SEAMING – A bending and flattening of an interlocking fold, e.g., a stove pipe seam.

SEAM WELDING – Process of closing a seam by a continuous resistance weld.

SEASONING – Process by which the internal stresses existing in a piece of material (which have been subjected to sudden changes of temperature, as in casting or hardening or have been acted upon by heavy forces in some machining operations) are removed.

SEMI AUTOMATIC – A process in manufacturing that requires some degree of manual input, but acts without this input for at least part of the cycle.

SERRATING – Method of forming by the use of a knurling tool a series of straight serrations on the outer surface of a part, and parallel with it along the axis of a part.

SHAPING – Operations performed on shaping machines.

SHAVING – A finishing operation that cuts a small amount of material from the edge of a stamping to gain finish, accuracy and / or a square edge.

SHEARING – Cutting in a line by two opposed blades somewhat in a manner of the ordinary household shears.

SHELL MOULDING – A form of gravity casting process metal (usually a high melting temperature metal) in which the mould is made of a thin shell of refractory material.

SHIELDED ARC WELDING – Process in which the molten weld metal is protected from deterioration by an envelope of chemically reducing or inert gas such as helium or argon.

SHRINKAGE FIT – Method of fitting a shaft or other part into an undersized hole by heating the outer member until has expanded sufficiently.

SHOT PEENING – A cold working process in which the surface of a finished part is pelted with finely ground steel shots or glass beads to form a compression layer.

SILVER BRAZING – Brazing similar or dissimilar materials by using an alloy of silver or other metals.

SINTERING – The process of fusing compacted material such as metal powders into a solid or porous piece by applying heat sufficient to bond, but not melt, the particles.

SLOTTING – Machine tool operation designed for finishing slots or other enclosed parts not capable of being machined by normal planning or shaping machine.

SLUSH DIE CASTING – Casting process which involves the filling of a metallic mould with liquid metal or alloy, then inverting the mould and pouring out the unfrozen metal from the center.

SMELTING – The process of heating ores to a high temperature in the presence of a reducing agent such as carbon (coke) and of a fluxing agent to remove the gangue.

SOLDERING – Operation of joining two or more parts together by molten metal.

SPINNING – Cold drawing ductile sheet metal blanks into cylinders and other shapes having rotational symmetry in a spinning lathe.

SPOT WELDING – Method of uniting sheet material by a series of localized welds, produced by overlapping the edges of two sheets of metal and fusing them together between copper electrode tips at suitably spaced intervals, by means of a heavy electrical current. It is a form of resistance welding.

STAMPING – Process of shaping metal under a falling weight.

STUD WELDING – Method of attachment of studs, screws, pins and similar parts to plates and components by projection welding or arc welding.

SUNDERLAND PROCESS – Method of generating gears by the use of a rack shaped cutter.

SURFACE GRINDING – Method of grinding designed to carry out the removal of metal from the surface of a part or parts less expensively, and with greater precision than could be achieved by machining processes with cutting tools of steel or by hand or machine filing.

SURFACING – Movement of a lathe tool at right angles to the bed, to work on the face or end surface of the work.

SWAGING – Compacting or necking down metal bars or tubes by hammering or rotary forming.

SWEDGING – A cold die forging operation in which the metal is confined and made to flow plastically into the punch and/or die impressions.

TAPER FIT – Type of fit in which a taper on the mating surfaces is combined with an interference fit between the parts when assembled.

TAPER TURNING – Method of turning a taper on a work in the lathe.

TAP GRINDING – Sharpening of a tapping tool by grinding a taper on the end and a clearance behind the cutting edge along this taper.

TAPPING – Operation of producing an internal thread by means of a tap.

TEMPER ROLLING – Process used in the production of tin -plate, in which the annealed coils or strips are subjected to a small amount of cold reduction in a four high mill in order to increase the stiffness of the dead soft material without unduly reducing its ductility.

THERMIT WELDING – Method of uniting iron or steel parts by surrounding the joint with thermit mixture at a sufficiently high temperature to fuse the adjacent surfaces of the parts together.

THREAD GRINDING – Grinding of screw threads so as to remedy such main variations in form or size as may have occurred as a result of the hardening treatment of a part or tool.

THREAD MILLING – Operation of producing threads, both external and internal, by means of thread milling cutters, either single or multi-ribbed, according to the type of thread required and the design of the thread milling machine employed.

THREAD ROLLING – Method of producing threads on screws, bolts, screw caps etc. by rolling under pressure so as to make contact with the rollers, to which the required pitch and form of screw threads have previously been given.

TONGUE SHAPING – Forming a narrow projection (called a tongue) from solid metal on a shaping machine.

TREPANNING – Removal of a circular piece of material from inside a steel bar, plate or billet.

TRIMMING – Cutting away excess material left from previous operations.

TUMBLING – Process of cleaning, polishing, or crushing in which the articles to be treated are mixed with balls, pieces of hard material or abrasive and rotated in a more or less horizontal container.

TURNING – Process of reducing the diameter of materials held in a lathe and the general name given to the process whereby material which is turned by means of a driven spindle to which it is attached, is brought into contact with a stationary tool having cutting edges.

UPSETTING – Process of increasing the cross-sectional dimensions when forging, with consequent reduction in length. May be done manually or by machine.

UPSET FORGING – The process of increasing the cross-section of stock at the expense of its length.

VULCANIZATION – The process of treating crude or synthetic rubber or similar plastic material chemically to give it useful properties, such as elasticity, strength and stability.

WELDING – Joining of metals by the application of heat, without the use of solder or any other metal or alloy having a lower melting point than the metals being joined.

WHEEL TRUING – Cutting off irregularities on a rotating grinding wheel with a diamond dresser.

WORM GRINDING – Grinding the threads of worm gear wheels as a means of finishing them after the hardening operation.

WIRE DRAWING – Reduction in diameter of metal rods by drawing them through conical openings in the blocks.

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