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Common Mechanical Engineering Terms (n) A simple mechanical arrangement used to hold a moving part in a . (see above for individual definitions). Department of Aerospace and Mechanical Engineering. University of .. My personal definition of Mechanical Engineering is web version, not the pdf version), you can double click the table to open the Excel spreadsheet). Mech. Eng. Top ASME Survey. Automobile: High-power lightweight engines, efficient mass- Computer-aided engineering technology: Computer-aided.
Jazib Saeed Khan Basics of Mechanical Engineering Basics of mechanical engineering with introduction to all courses, subjects, topics and basic concepts - I have personally interviewed many mechanical engineers for jobs at various companies. During several interviews, I have observed that many job seekers give incomplete answers or wrong answers to some of the technical questions asked during interview. This gives a very bad impression and chances of losing the job opportunity increase. Here on this mechanical engineering website, I have compiled all the basic concepts of courses taught in mechanical engineering degree. Some important subjects have already been added and more mechanical engineering courses will be added soon. It is advisable for all mechanical engineers to keep on revising these concepts.
It has very good permeability and moderate binding qualities. Used in ground form in cores and moulds to increase hot compressive strength. Iron which contains little or no carbon. It is very soft and ductile and is known as alpha iron. A magnetic form of iron. In some cases the ferroalloys may serve as deoxidizers. A reinforced plastic manufacturing material with many applications. FILTER — In radiography a device, usually, a thin metallic layer inserted into a beam of radiation so as to modify the transmitted spectrum of radiation.
It may be used to enhance or reduce contrast or minimize undesirable scattered radiation. FIXER hypo — A photographic processing solution, the principle function of which is to dissolve the undeveloped silver halide grains from the developed film, thus making the image more prominent. It often serves also to harden the gelatine and halt the developing process. FLUX — A solid, liquid or gaseous material that is applied to solid or molten metal in order to clean and remove oxides.
Foam rubbers are formed by the inclusion of chemicals in rubber compounding which form gases during vulcanization. Often used in wire form for jewellery and decorative applications. GLASS — Transparent substance produced by the fusion of sand and certain metallic salts, of which soda compounds are most common. Glue laminated beam will support large loads and can span long distances with only end support.
GRIT SIZE — Nominal size of abrasive particles in a grinding wheel corresponding to the number of openings per linear inch in a screen through which the particles can just pass. It is useful in estimating radiographic exposure. HINDU MINIUM — A high strength aluminium alloy containing, in addition to aluminium, magnesium, iron, titanium, copper, nickel and silicon, which after heat treatment has a strength exceeding that of mild steel. INGOT — A large block of metal that is usually cast in a metal mould and forms the basic material for further rolling and processing.
ION — An atom, or group of atoms, that has gained or lost one or more outer electrons and thus carries an electric charge. Positive ions, or cations, are deficient in outer electrons. Negative ions or anions, have an excess of outer electrons, thus ion is electrostatically charged.
It is suitable as a gamma radiation source, mostly in radiography. Pure iron consists of homogenous crystal grains generally referred to as ferrite. IRON wrought — Malleable iron produced from molten pig iron by a working or puddling process which removes the impurities.
About 25 per cent Cr, 5 per cent Al, 3 per cent Co, and balance almost pure iron. KAOLIN — A fine white clay that is used in ceramics and refractories composed mostly of kaolinite, a hydrous silicate of aluminium. Impurities may cause various colours and tints. KILLED STEEL — Steel that has been deoxidized with agents such as silicon or aluminium to reduce the oxygen content to such a level that no reaction occurs between carbon and oxygen during solidification.
This prevents gases from evolving during solidification. 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. 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 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.
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. 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. Widely used for aircraft components, their weight is only two thirds that of aluminium, and a quarter of that of steel.
The graphite is in the form of temper carbon. This is less brittle than gray cast iron. Martensite is the hardest of the transformation products of austenite, having an acicular or needle like microstructure. The three forms of matter are solids, liquids and gases. Examples are sulphur, silicon, carbon, phosphorous and arsenic. It gives red hardness and increases the strength of steel at high temperatures. It increases the corrosion resistance of stainless steels at high temperatures, increases the machinability of carbon steels and reduces the temper brittleness of aluminium steels.
MU METAL — Special alloy of nickel and iron, also containing copper and manganese, requiring only a very small magnetizing force to produce a normal flux density i. MYCALEX — It is the trade name for a ceramic product made up of glass- bonded mica flakes that possess a combination of properties found in other insulating materials. Crude rubber is coagulated by heat or by addition of electrolytes.
Used for under-water fittings of marine craft. NICHROME — Alloy of nickel and chromium which is practically non- corrosive, can withstand high temperature without oxidation and is used for furnace components. Therefore, used in pure form for some applications, such as plating.
It is more usually alloyed with other metals. Class of alloys used in the manufacture of electrical resistance coils and elements, decorative articles for which its lustrous colour which increases in whiteness with nickel content make it very suitable, or for heavy duty works such as high pressure steam fittings. A typical composition is 30 Handbook of Mechanical Engineering Terms 1.
This has high carbon content, averaging between 2. It is somewhat brittle. In many plant cells, the cellulose wall is strengthened by the addition of lignin, forming lignocellulose. It is characterized by an orthorhombic crystal structure. When it occurs as a phase in steel, the chemical composition will be altered by the presence of manganese and other carbide forming elements.
CESIUM 13T — A radioisotope, recovered as a fission product from nuclear reactors, with a half-life of 33 years and a dominant characteristic gamma radiation of 0.
It is suitable as a gamma radiation source, especially in radiography and therapy. CHILL — 1 A metal insert embedded in the surface of a sand mould or core or placed in a mould cavity to increase cooling rate at that point. A similar microstructure is found in cast magnesium alloys containing silicon as Mg2Si.
The bonding may have been accomplished by rolling, welding, casting, heavy chemical deposition or heavy electroplating.
COAL TAR — Also called crude oil, when subjected to fractional distillation and purification, yields a variety of useful products-neutral, acidic, and base oils. It is used as a gamma radiation source in industrial radiography and therapy. An example is carbon fibres in an epoxy matrix.
Loads applied to the structure are carried by the fibres. COPPER — A reddish, soft, ductile metal with very good heat and electrical conductivity and is the basic element in brass and bronze.
CORE — 1 In a metal casting, the hollow parts which cannot be shaped as easily by the pattern that are made by using formed sand shapes, that are strengthened by baking or by using epoxy. Rock sand, river bed and sea shore sand, commonly known as sharp sand, used for making of cores in the foundry because they are capable of withstanding high temperatures, and resisting the penetrating action of the molten metal.
It has high electrical conductivity and high temperature resistance. This steel is used for tools, dies and better grades of cutlery. CUNIFE — Cunife is a copper-nickel iron alloy that is malleable, ductile and machinable, even in an age-hardened form. Magnets are formed from wire stock in round, square, or rectangular form. CURIE — The quantity of a radioactive nuclide in which the number of disintegrations per second is 3.
Dendrite generally grow inward from the surface of a mould. Used as a cutting tool, and a grinding tool and to dress grinding wheels. DROSS — The scum that forms on the surface of molten metals largely because of oxidation but sometimes because of the rising of impurities to the surface. This demands a sand that when dried or baked will give strength, porosity and permeability.
DURALUMIN — Aluminium alloy containing copper, manganese and magnesium, which can be cast, forged or stamped, and is widely used for sheets, tubes, forgings, rivets, nuts, bolts and similar parts.
EUTECTIC — Mixture an alloy in which the proportions of the constituents are such that the mixture has a lower melting point than any of the constituents. It has very good permeability and moderate binding qualities. Used in ground form in cores and moulds to increase hot compressive strength. Iron which contains little or no carbon. It is very soft and ductile and is known as alpha iron. A magnetic form of iron. In some cases the ferroalloys may serve as deoxidizers.
A reinforced plastic manufacturing material with many applications. FILTER — In radiography a device, usually, a thin metallic layer inserted into a beam of radiation so as to modify the transmitted spectrum of radiation. It may be used to enhance or reduce contrast or minimize undesirable scattered radiation. FIXER hypo — A photographic processing solution, the principle function of which is to dissolve the undeveloped silver halide grains from the developed film, thus making the image more prominent.
It often serves also to harden the gelatine and halt the developing process. FLUX — A solid, liquid or gaseous material that is applied to solid or molten metal in order to clean and remove oxides. Foam rubbers are formed by the inclusion of chemicals in rubber compounding which form gases during vulcanization.
FREE FERRITE — Ferrite that is structurally separate and distinct as may be formed without the simultaneous formation of carbide when cooling hypoeutectoid austenite into the critical temperature range. Often used in wire form for jewellery and decorative applications. GLASS — Transparent substance produced by the fusion of sand and certain metallic salts, of which soda compounds are most common.
Glue laminated beam will support large loads and can span long distances with only end support. GRIT SIZE — Nominal size of abrasive particles in a grinding wheel corresponding to the number of openings per linear inch in a screen through which the particles can just pass. It is useful in estimating radiographic exposure. HINDU MINIUM — A high strength aluminium alloy containing, in addition to aluminium, magnesium, iron, titanium, copper, nickel and silicon, which after heat treatment has a strength exceeding that of mild steel.
INGOT — A large block of metal that is usually cast in a metal mould and forms the basic material for further rolling and processing. ION — An atom, or group of atoms, that has gained or lost one or more outer electrons and thus carries an electric charge.
Positive ions, or cations, are deficient in outer electrons. Negative ions or anions, have an excess of outer electrons, thus ion is electrostatically charged. It is suitable as a gamma radiation source, mostly in radiography. Pure iron consists of homogenous crystal grains generally referred to as ferrite. IRON wrought — Malleable iron produced from molten pig iron by a working or puddling process which removes the impurities.
About 25 per cent Cr, 5 per cent Al, 3 per cent Co, and balance almost pure iron.
KAOLIN — A fine white clay that is used in ceramics and refractories composed mostly of kaolinite, a hydrous silicate of aluminium. Impurities may cause various colours and tints. KILLED STEEL — Steel that has been deoxidized with agents such as silicon or aluminium to reduce the oxygen content to such a level that no reaction occurs between carbon and oxygen during solidification. This prevents gases from evolving during solidification. 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.
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 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.
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. 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. Widely used for aircraft components, their weight is only two thirds that of aluminium, and a quarter of that of steel. The graphite is in the form of temper carbon. This is less brittle than gray cast iron.
Martensite is the hardest of the transformation products of austenite, having an acicular or needle like microstructure. The three forms of matter are solids, liquids and gases.
METAL — An opaque lustrous elemental chemical substance that is a good conductor of heat and electricity and when polished , a good reflector of light. Examples are sulphur, silicon, carbon, phosphorous and arsenic. It gives red hardness and increases the strength of steel at high temperatures. It increases the corrosion resistance of stainless steels at high temperatures, increases the machinability of carbon steels and reduces the temper brittleness of aluminium steels.
MU METAL — Special alloy of nickel and iron, also containing copper and manganese, requiring only a very small magnetizing force to produce a normal flux density i. MYCALEX — It is the trade name for a ceramic product made up of glass- bonded mica flakes that possess a combination of properties found in other insulating materials.
Crude rubber is coagulated by heat or by addition of electrolytes. Used for under-water fittings of marine craft. NICHROME — Alloy of nickel and chromium which is practically non- corrosive, can withstand high temperature without oxidation and is used for furnace components. Therefore, used in pure form for some applications, such as plating. It is more usually alloyed with other metals. Class of alloys used in the manufacture of electrical resistance coils and elements, decorative articles for which its lustrous colour which increases in whiteness with nickel content make it very suitable, or for heavy duty works such as high pressure steam fittings.
The commonly used grades contain 0. NOMAG — Non-magnetic cast iron, used for castings in electric motors and alternators and similar applications. NUCLEUS — 1 The first structurally stable particle capable of initiating recrystallization of a phase or the growth of a new phase and possessing an interface with the parent matrix. NYLON — A group of plastics of nitrogenous structure known as polyamides which are crystalline in nature and can be so processed as to orient the crystals axially thus making the tensile strength of fibres extremely high.
ORE — A natural mineral that may be mined and treated for the extraction of any of its components, metallic or otherwise. PHASE — It is a portion of matter which is homogeneous in the sence that its smallest adjacent parts are indistinguishable from one another. PHASE DIAGRAM — Phase diagram is also called equilibrium diagram or constitution diagram, indicates the relative amount and composition of phases present in an alloy at a given temperature and pressure, when the alloy is in equilibrium.
Its formula weight is Used as bearing material. PHOTON — The smallest possible quantity of an electromagnetic radiation that can be characterized by a definite frequency. PIG IRON — Iron produced from iron ore in the blast furnace, basic raw material from which all cast iron, wrought iron and steel are made.
Usually contains about 4. Plasma arcs are used in welding, cutting and machining processes. PLASTIC — A certain group of natural and synthetic resins and their compounds that can be moulded, cast, extruded or used for coatings and films. It is extensively used, either solid or clad, for chemical equipment. In combination with glass fibres they form a product which has an outstanding strength- weight ratio. POLYMER — A chemical compound or mixture of compounds formed by polymerization and consisting essentially of repeating structural units.
It is found in nature as radium , which has a half-life of years. These materials are usually silica, fire clay, diaspore, alumina and kaolin. They are used for furnace linings. RESIDUE — The material that remains after completion of a chemical or physical process, such as combustion, distillation, evaporation or filtration. When the mould top is not capped, a side and bottom rim of several centimeters forms.
The solidified ingot has got scattered blow holes and porosity in the center but a relatively thick skin free from blow holes. RUST — A corrosion product containing hydrated oxide of iron. Applied only to ferrous alloys. SAND moulding — Substance used in foundries for making the moulds. These contain a few electrons to give them conductivity intermediate between metals and insulators. SEMISTEEL — Cast iron to which a small proportion of mild steel or wrought iron scrap is added during the melting of the pig iron so that the product will have a lower carbon content than the average iron, from 2.
SILMANAL — It is the name given to a rather expensive alloy of silver, manganese, and aluminium that has unusual magnetic properties for special applications.
SLAG — The more or less completely fused and vitrified matter separated during the reduction of a metal from its ore. Also a mixture of fog and smoke. Particles suspended in air after incomplete combustion of materials containing carbon. The matter in the exhaust emission which obscures the transmission of light.
Soft solder is an alloy of lead and tin, in which the proportions of the two constituents may vary from almost pure lead to almost pure tin.
STEATITE — Steatite is the name given to a fired ceramic product which contains 80 per cent or more talc bonded with ceramic fluxes to a non- porous structure. The alloy steels contain substantial amounts of alloying elements such as chromium or nickel besides carbon. THERMIT — Powdered form of finely divided iron oxide and aluminium which burns intensely to produce superheated liquid steel at a temperature of about TIN — A silvery white, soft metal used in solders and as a plating material.
TOOL STEEL — A special group of steels that is designed to specific uses, such as heat resistant steels that can be heat treated to produce certain properties mainly hardness and wear resistance. Used as an alloying element in high speed steel.
Usually contains less than 0. It is tough, malleable, and relatively soft. Rolled steel is strongest in the direction of rolling. BEL — A unit denoting the ratio of power levels of signals or sound. The number of bels may be given as the common logarithm of the ratio of powers. A number is derived by measuring the indentation with a special microscope. Brittleness is opposite to plasticity. It is one type of crystalline fracture.
Material Properties COUPON — A piece of metal from which a test specimen is to be prepared, often an extra piece as on a casting or forging. CREEP — Slow plastic deformation in steel and most structural metals caused by prolonged stress under the yield point at elevated temperatures. More accurately defined as the amount of work dissipated into heat by a unit volume of material during a completely reverse cycle of unit stress. DUCTILITY — The property of a material to deform permanently or to exhibit plasticity, elongation or bending or twisting without rupture breaking or cracking while under tension.
In mild steel, the fatigue strength is about 50 per cent of the tensile strength. It forms a body centered cube lattice and may hold in solution considerable amounts of silicon, nickel or phosphorous. Usually refers to unnotched tensile specimens. GRAIN SIZE — For metals, a measure of the area or volume of grains in polycrystalline material, usually expressed as an average when the individual sizes are fairly uniform.
Reported in terms of number of grains per unit area or volume, average diameter, or as a grain size number derived from area measurements. GROWTH — With reference to cast iron, permanent increase in volume that results from continued or repeated cyclic heating and cooling at elevated temperatures.
This is divided into three categories, resistance to penetration, resistance to abrasion and elastic hardness. The presence of excess amounts of sulphur in steel causes hot shortness.
This test determines the notch toughness of a metal.
KISH — Graphite thrown out by liquid cast iron in cooling. 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. Ratio of stress, within proportional limit, to corresponding strain. In metals, over oxidation during heating under oxidizing conditions often results in permanent damage to metals.
PH — The negative logarithm of the hydrogen ion activity. It denotes the degree of acidity or basicity of a solution. PERMANENT SET — When a metal remains deformed from its original dimensions after the forces applied to it have been reduced to zero, it is said to have undergone plastic deformation, and the amount of deformation is called the permanent set. The following phases occur in the iron carbon alloy, molten alloy; austenite, ferrite, cementite, and graphite.
The direction of the strain is dependant upon the polarity of the field. Clay is completely a plastic material. Metals exhibit plasticity in varying amounts. The proportional limit is high for steels and low for cast iron, copper, and aluminium.
Several scales are used to cover very soft to very hard materials. The Rockwell C scale is used mostly for steel. SHEARING — A concentration of forces in which the bending moment is virtually zero and the metal tends to tear or to be cut along a transversal axis at the point of applied pressure.
It is designated as cold, hot and red to indicate the temperature range in which the brittleness occurs. SLAG dross — A fused product that occurs in the melting of metals and is composed of oxidized impurities of a metal and a fluxing substance such as limestone.
The slag protects the metal from oxidation by the atmosphere since it floats on the surface of the molten metal. These are lines that appear on the polished surface of a plastically deformed metal.
The slip bands are the result of crystal displacement, defining planes in which shear has taken place. Some of the types of solid solutions are continuous, intermediate, interstitial, substitutional and terminal. SOLIDUS — Seen as a line in a two phase diagram, it represents the temperatures at which freezing ends when cooling, or melting begins when heating under equilibrium conditions.
The specific gravity for pure water is taken as 1. An aggregate of globular carbide is formed from other microstructures such as pearlite. For identical shapes, the stiffness is proportional to the modulus of elasticity. This is unit deformation of a metal when stress is applied. It is called tensile, compressive, or shear strength depending on the load. The force tends to cause the plane of the area involved to slide on the adjacent planes.
Stress raisers pose a particular problem and can cause early failure in members that are subjected to many cycles of stress reversals. This treatment is used to relieve stresses caused by welding, cold working, machinning, casting and quenching.
An alloy may be cold worked to the hard temper, fully softened to the anealed temper, or two intermediate tempers. All materials are in some measure conductors of heat. The difference of expansion and contraction between the interior and exterior surfaces of a metal that is being heated or cooled is an example.
Work per unit volume required to fracture a metal and is equal to the area under the stress strain curve. The highest strength that a metal exhibits after it begins to deform plastically under load.
Rupture of the material occurs either at the peak of its ultimate strength or at a point of further elongation and at a drop in stress load. The inert gases have zero valence, valence is determined by considering the positive and negative atoms as determined by the atoms gaining or losing of valence electrons. VISCOSITY — The property of the fluids, either liquid or gaseous, which causes them to resist instantaneous change of shape or instantaneous rearrangement of their parts, due to internal friction.
VOID — A cavity or hole in a substance. WEAR — A surface deterioration of contacting surfaces that destroys their operating relationship, or causes rupture if carried far enough. This phenomenon is not seen in non-ferrous metals and other alloy steels. 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.
The hole material is saved and used for further operation. 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.
Strain hardening occurs as a result of this permanent deformation. 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.
Processes 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. 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.
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. 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.
DRAWING — Process, in press work, which involves reducing the diameter or cross-sectional dimensions of a cup, shell, tube, bar or wire. 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. 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.
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. A filament of the fibre is wound around a form, then bonded in place with the resin matrix.
A flange may drawn 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. 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.
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.
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.
Bonding results from interlocking of the atoms of each piece with some additional interlocking introduced by diffusion. 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. 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.
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.
A millwright is a craftsman in the true sense of the word. Peening introduces compressive stresses on weld surfaces that tend to counteract unwanted tensile stresses. 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 planing machine.
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. The hole material is scrapped. It is a shearing operation carried out in a press. Also refers to the refining of the grain of a coarse grained metal or alloy. It may be either a hot or cold working process.
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.
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. 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 planing or shaping machine. 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. 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. 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. 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.
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. May be done manually or by machine.
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. 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. It is a group of electric cells connected together. Machines and Devices 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.
In one type, the spindle only rotates and in another type the spindle rotates and also has a horizontal movement. The chief feature is the provision of special hand operated rests. The machine comprises a fast and a loose head stock, and a base plate upon which the bed is mounted. The fuel is ignited by the heat of compression only.
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. This enables two face mills or two horizontal cutters, to work simultaneously on opposite sides of the workpiece. This permits several drilling operations to be made by moving the workpiece from spindle to spindle in a planned sequence. This helps protect the gauge.
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.
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. It is a strong, heavily built and a rather slow-moving machine, and the standard range varies from tons per sq.
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. The tool to be ground is secured in a chuck having a range of adjustments such that any desired angle can be ground.
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. The machine comprises a small punch moving up and down at high speed, and so taking a considerable number of small nibbles or cuts.
It comprises a bed, a travelling worktable on which the parts to be planed are carried, standards, a cross slide, tool box and gearing. 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. It may be of the crank or eccentric variety; the frame of the C or double sided type.
In this the drill spindle could be moved to the positions required instead of moving the work for each hole to be drilled. 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.
RELAY — An electromagnetic switch which utilizes variation in the strength of an electric circuit to effect the operation of another circuit. Excessive pressure opens the valve and releases some of the gas or liquid. May be classified according to the method of operation hydraulic, pneumatic, or steam and the manner in which the rivet head is formed.
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. Cams control the movement of the cutting tools, attachments and stock feeding devices to complete workpieces automatically at high production rates.
In this the ram which carries the tool reciprocates while the worktable which carries the workpiece moves perpendicular to the ram movement. It comprises a fixed blade and a shearing tool or blade. There are two types—horizontal and vertical.
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. The main difference between them is that the turret saddle has longitudinal movement on the guides of the bed.
Provided with a swivel table and headstock and a wheel head that can be rotated on its base. APRON — The function of a lathe apron is to carry the mechanism for sliding and surfacing motions and screw cutting. 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. 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.
The large crank gear of a shaper is often called a bull wheel. CAP SCREW — A finished screw, used for fastening two pieces together by passing the screw through a clearance hole in one part and screwing it into a tapped hole in the other. Heads may be hexagon, round, flat, fillister or socket type. The carriage carries the cutting tool and moves along the ways of the lathe. It contains the saddle, compound slide, and apron. Change gears on a lathe make it possible to cut threads of different pitches and obtain different feeds per revolution.
On milling machines they are used to obtain different leads when milling spirals and helices. A clapper block is hinged into the clapper box to permit the cutting tool to swing upward on the return stroke. COLLET — Means of gripping a bar to give quicker chucking, particularly in capstan work for rapid and accurate setting.
The lower part or base is graduated in degrees and can be swivelled to any angle for turning short tapers and angles.
The upper slide carries the tool post and tool holder. Also the exact or precise center of an object. The die head consists of a cylindrical body with a shank to enable it to be clamped in the turret.
DIVIDING HEAD — Indexing or dividing head is an attachment used on the milling machine table, for accurately dividing the circumferences of components for grooving or fluting, gear cutting, cutting of splines, squares or hexagons. DOG — A tool or accessory which can be clamped on a workpiece to drive it while held between centers, as a lathe dog. Also, the name given to a projecting part on a machine tool which strikes and moves another part, such as the reversing dogs on a grinding machine or planer.
DRILLING JIG — Device, usually of hardened steel plate, for holding a piece of work in a definite position, provided with guide bushes through which drills can pass so as to locate holes in exact positions in the work. One end is tapered outside to fit the drilling machine spindle hole while the opposite end has a larger taper hole to receive the cutting tool shank.
It is similar in principle to a spring collet. Three jaws are arranged to expand outward and clamp the work, as a tapered pin is forced inward. FEATHER — A sliding key sometimes called a spline, used to prevent a pulley, gear, or other part from turning on a shaft, but allows it to move lengthwise. The rest is attached to the carriage and set close to the cutting tool.
It travels along with the cutting tool to prevent the work from springing away from the cutting tool. Machine Components and Attachments It contains a center for supporting the workpiece, the same as the tailstock does for a lathe.
FOUR JAW CHUCK — A chuck that provides a more powerful grip on the work by means of four jaws which may be adjusted independently, so that irregular shapes may be gripped, and the fact that the jaws can be reversed enables the work to be gripped inside as well as from the outside. 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.
The lever opens and closes a nut that has been split lengthwise so that the two halves of the nut can be closed upon the lead screw when threads are being cut. These gears have no effect on the speed or ratio between the driver and driven gears. A pin on the crank fits into the holes of the index plate. It is attached to the index head and used for obtaining fractional parts of a turn of the index crank.
A set of three or more index plates may be furnished for an index head. JIG — A device that locates and holds a workpiece and guides the cutting tool. KEYS — Metal pieces of various designs which 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. KNEE — A principal part of a column and knee type milling machine which slides vertically on the column and carries the saddle and table.
This enables the bar to revolve between the centres. 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.
MANDREL — A turned, hardened and accurately ground cylindrical bar or shaft or spindle, incorporating a slight taper, used for holding bored parts in a lathe while the outside surface is being turned. A vertical attachment makes it possible to do vertical milling on a horizontal machine. NUT — A metal fastener of square, hexagon or other shape having an internal thread which screws onto a bolt, stud, or arbor.
This comprises a pair of half-nuts capable of sliding in vertical slides in or out of mesh with the lead screw. PILOT — A guide at the end of a counterbore which fits freely into the drilled hole to hold and align the body of the counterbore while cutting takes place. These are operated with auxiliary power such as compressed air or oil pressure.
Where simplicity of chucking is the first consider- ation, magnetic chucks are used. RACK — A straight metal strip having teeth that mesh with those of a gear to convert rotary motion into reciprocating motion or just the opposite. A scale graduated in degrees permits the work to be moved any number of degrees for spacing holes or milling radii.
SET SCREW — Usually a hardened steel screw having either no head or a square head and with various designs of points or ends to lock or tighten adjustable machine parts in position on a shaft. The screw body is slightly longer than the thickness of the piece pivoted on the screw so as to allow the piece to move freely when the screw is set up tightly against the bottom of the shoulder. SLEEVE — A round piece of metal having a straight or tapered hole which fits over or into another piece to adapt parts to fit, as a taper sleeve for a lathe center.
It is usually adjustable for holding and guiding cutting tools. The compound slide or rest used on an engine lathe is an example. The compound slide permits the tool to be fed at any angle. SNAP FLASK — Strongly constructed wooden moulding box, split diagonally with hinges on one corner and locking latches on the opposite corner, so that the box may be removed from the mould prior to casting.
SPLINES — Multiple keys cut in either a shaft or a hole of parts that are made to slide or move lengthwise on a shaft, as a sliding gear transmission. Used to prevent slender work from springing away from the cutting tools or to permit machining operations to be performed on the end of the workpiece. STOPS — Devices attached to the movable table or ram or parts of a machine tool, such as a milling machine table, to limit the amount of travel.
STUD — A plain cylindrical piece having a threaded portion of suitable length at each end or a continuous thread over the entire length. One end is screwed into a machine or workpiece after which a second part is placed over the stud and held in place by a nut.
May be moved along the ways and clamped in different positions and offset from the true axis of the lathe for turning tapers. THREAD CHASING DIAL — A device consisting of a short shaft with a dial at the top and a worm gear at the bottom to mesh with the lead screw on an engine lathe which is attached to the lathe carriage, so that the operator can engage the split nut lever at the correct position when cutting screw threads.
TOOL HEAD — The part of machine tool that carries the cutting tool and is adjustable for moving and setting the cutting tool into the workpiece being machined. 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 workpieces.
Used to reverse the direction of rotation of the lead screw for thread cutting or the feed rod for turning. U-CLAMP — A flat or square piece of metal bent or formed into the shape of the letter U and used for clamping workpieces on a machine table.
Also called concentric chuck or self centering chuck. VICE — A mechanical device of many designs and sizes in which workpieces are clamped for hand and machine operations.
V-WAYS — The top part of the bed of a lathe, planer or other machine bed which acts as a bearing surface for aligning and guiding the moving parts, such as the carriage of a lathe. The term angle cutter covers three types of milling cutters, the single or half-angle, the double angle and the equal or combined angle.
This hand-drill has double ratio drive. BROACH — A long tool with number of cutting teeth which is pushed or pulled through a hole or across a surface to form the desired shape and size.
Tools and Cutters The end of the chisel is shaped to the required form and finished by grinding. It consists of a series of blades arranged to cut on the ends only, and a smooth pilot slightly smaller than the drilled hole.
DIE drawing — Tool of angular form through which a shell is pushed, tubes, sections, bar and wire are pulled so as to give the required size and cross-sectional shape.
DIE NUT — Tool, shaped like a square or hexagonal nut, and provided with cutting edges, employed for cutting or sizing external threads. DIE PLATE — Tool in the form of a flat plate of good quality cast steel having a number of drilled and tapped holes, employed in hand cutting screw threads on rods of about 5 mm in diameter or smaller. DOT PUNCH — Light type of sharply pointed centre punch used for light centre dotting along a scribed line to make it more easily visible or to ensure a permanent record of its location.
The cutting portion has teeth on the end as well as on the circumference. A hole is drilled into or through the portion of the stud remaining in the hole. Then the exy out is screwed into the hole and when the tool is turned counter clockwise, the broken portion is removed from the hole. FILE — Steel tool used for smoothing rough surfaces, and for reducing the thickness of material by abrasion. The teeth may be single cut or double cut.
FLAT DRILL — Type of drill in general use before the introduction of the twist drill, having flat sides and, therefore, no true cutting action, the flat drill is inclined to have a scraping action rather than cutting. FLAT FILE — General utility file having a rectangular section, parallel in both width and thickness for about two thirds its length and slightly tapered off in both width and thickness towards the point for the rest of its length.
They are double cut on their wide working faces, but are single cut on both their narrow edges. Intended for removing a small amount of metal and for finishing a hole accurately and smoothly. The cutting tool is ground to the shape desired and reproduces this shape on the workpiece. FULLER — Tool used by the smith for making rivetted joints or shaped work on the anvil, or working under the power hammer. The elements that make up the wheel are 1 abrasive, 2 grain size, 3 bond, 4 grade and 5 structure.
There are nine standard shapes and many sizes and grades for grinding practically all kinds of materials. HAMMER sledge — Tool with a steel head and a wooden handle, a larger type of hammer which may have the head weighing from, say 2 to 7 kg with the handle varying from, say 60 to 90cm in length.
These are used only for small threads on brass, or for rounding off the tops and bottoms of threads previously formed by the vee tool in the screw cutting lathe. HAND FILE — Commonly used file parallel in width from the tang to the tip, but slightly thinned off in thickness for about one third of its length towards the point. It has a thread cut on it, and is fluted to provide cutting edges.
A square at the shank end makes it possible to attach a wrench for turning by hand. HAND TOOL — A general term that applies to wide variety of small tools used by hand instead of being power driven, as layout tools, wrenches and hammers. HOB — Fluted rotary cutter used to produce spur, helical, and worm gears, a worm shaped cutting tool having a number of flutes or gashes running across the threads so that a series of cutting edges is formed.
Mating sections are similar to half side cutters or staggered tooth side cutters with uniform or alternate helical teeth so designed that the paths of teeth overlap when in proper assembly. LAP — A tool for finishing internal and external surfaces of the workpiece by charging the lap with a fine abrasive. Always made from metals which are softer than the metal being lapped. For milling cutters, when viewed from the spindle or shank end, the cutter would turn counter- clockwise.
PIN PUNCH — Type of punch, sometimes called a drive pin punch, employed in removing dowel pins, cotter pins, rivets and similar light objects used as temporary fastenings, also for punching small holes in sheet metal. REAMER — Multiedged cutting tool having cutting edges arranged down the length of the tool, the teeth and the flutes being either straight and parallel to the axis or alternatively helical with a lead opposite to the direction of rotation.
RIFFLER — File with a curved working surface specially made for filing concave surfaces, such as the insides of oddly shaped holes in castings. A cutter that rotates clockwise when viewed from the spindle end is said to have right hand rotation. A cutter has a right hand helix when the flutes slant downward to the right when viewed from the front or twist clockwise when viewed from the end.
With no side rake it may be used to cut either right or left hand. SCRAPER — Tool used to reduce the high spots on a surface which has previously been smoothed as far as possible by machining or filing. Scraping is hand operation. SCRIBER — Metal tool, shaped something like a thin pencil, having a sharply pointed end for marking lines on metal surfaces so as to locate the positions of holes, angles, machining boundaries.
SCRIBING BLOCK — Tool comprising a heavy base, a rigid vertical spindle and a sleeve device capable of travelling up and down the spindle and holding a scriber, used primarily on surface plates for the purpose of scribing lines parallel to a level surface or to another line.
SET — The bend to one side of the teeth of a saw. Also, any deformation of metal or other material stressed beyond its elastic limit. SHANK — The non-cutting end of a tool which fits into the holding device for driving, as the taper shank on a drill. The body of the cutter is slightly less in length than its diameter, and is made with a hole through the centre to fit a standard arbor.
The term shell is used to differentiate this type of reamer from the solid reamer. It is more of a milling cutter than a drill. SQUARE — The name of tools of various designs and types used for laying out, inspecting, and testing the squareness of workpieces. Also, lines or surfaces which meet at right angles. Used for chamfering or for rough cuts on flat surfaces where sharp corners are necessary. Also, used for finishing cuts on cast iron. The stock is the name given to the portion of the tool hand holder into which the dies are placed and which enables the dies to be rotated without undue effort.
The assembled unit is called die and stock. TANG — Two opposite flats milled at the end of taper shanks which enter a slot in the spindle to prevent slipping and provide a means of removing the shank from the spindle. Also the name of the part of a file that fits into the handle. TAP — A hardened and tempered steel tool for cutting internal threads which has flutes lengthwise to provide cutting edges for the threads and a square at the end of the shank for turning the tap with a wrench.
TAP DRILL — A twist drill, the size of which will produce a hole that can be tapped with a specified tap to give a thread of required depth or percentage of full depth.
Prongs extend down into the flutes of the broken portion. By attaching a wrench to the extractor, the broken part in the hole may be loosened and backed out.
It is chamfered at its small end for a distance equal to 4 or 5 times the distance between threads. This device is rotated in a drilling machine to cut out large circles or holes from solid metal by cutting a narrow groove around the metal.
These flutes leading from the cutting faces, called lips, provide an exit for the metal that is removed when the hole is being drilled.
Used for the fast removal of metal when slots or keyways are to be cut on the milling machine. WHEEL grinding — Power driven wheel consisting of abrasive particles, held together by artificial or natural, mineral, metal or organic bonds.
It is also used for setting the tool square with the axis of the workpiece. With this, it is possible to determine exactly the depth of cut taken. CALIPER — Instrument used for measuring distances between or over surfaces, or for comparing dimensions of workpiece with such standards as plug gauges, graduated rules etc.
They are used for dividing distances into a number of equal parts. Also used for transferring dimensions from a rule to the work. Also it may be called a drill point gauge or a drill angle gauge. They are used for checking clearances.
GAUGE — A tool or instrument for checking or measuring the sizes of metal parts to determine whether the dimensions are within the specified limits. INDICATOR — A sensitive instrument which shows slight variations when testing the trueness, or alignment of a workpiece, fixture or machine part such as a milling vice.
Dial indicators may be graduated to read small linear variations. Instruments and Gauges Vernier protractor is used for measuring angles accurately. These are useful for measuring in restricted places or on curved surfaces. 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.
ODD LEG — Caliper having one leg bent inwards at its ends, like the two legs on a pair of inside calipers, the other leg being pointed or having a separate hardened point attached to it. May be straight or tapered, plain or threaded, and of any cross-sectional shape. A ring gauge may be cylindrical or conical, plain or threaded. It is used to find the pitch and number of threads per inch on a screw, tap or die. 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 workpieces.
TRAMMELS — are generally used for laying off and checking dimensions of several feet, they are generally used in conjunction with a large steel rule, which may be from 3 to 10 ft long. One leg can be separated or opened to remove the caliper and then returned to the measured size. TRY SQUARE — Instrument used for setting and checking a line, an edge or a face which is required to be at right angles to some other plane which should be regarded as a datum or reference plane.
VERNIER — Small-scale, for making accurate measurement, carrying a certain number of graduations equalling in their combined length a different number of graduations, usually one more or one less, on the main scale of the instrument to which the vernier is attached.
AIR GATE — A vertical channel for the removal of gases from the mould; checking of the filling of the mould cavity with metal and feeding up the casting with metal during solidification.
It may be covered with a cope, or cast open, according to the type of work. May be cereal, oil, clay, resin, pitch etc. BLEED — Molten metal oozing out of a casting stripped or removed from the mould before solidification. Casting 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.
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.
Act of pouring molten metal into a mould. Molten metal is moved from the center to the periphery by centrifugal action. The mould can be made in a flask or in the form of a shell. CEREAL — Substance derived from corn flour, which is added to core and moulding sands to improve their properties for casting production.
After a short time, the penetrant seeps out of the cracks into the whiting, causing an appreciable difference in whiteness. CHILL — A metal object placed on the outside or inside a mould cavity to induce more rapid cooling at that point and thereby produce hard zone i.
CHILL TEST — Method of determining the suitability of a gray iron for specific castings through its chilling tendency, as measured from the tip of a wedge shaped test bar. Includes degating, tumbling, or abrasive blasting, grinding off gate stubs. COD — A sand projection left behind in the mould by some patterns. Strictly speaking it is a core. COPE — The upper or top most section of a flask, mould or pattern.
COPE false — A temporary cope which is used only to establish the parting line. CORE — Separable part of the mould, usually made of sand and generally baked, to create openings and various shaped cavities in the castings. Also used to designate the interior portion of an iron base alloy which after case hardening is substantially softer than the surface layer or case.
CORE ram up — Core attached to the pattern and rammed up in the mould, where it remains when the pattern is withdrawn. CRUSH — Casting defect appearing as an indentation in the surface due to displacement of sand in the mould, usually at the joint surfaces. CUTS — Defects in castings resulting from erosion of the sand by the molten metal pouring over the mould or core surface. DIRT — Any extraneous material entering a mould cavity and usually forming a blemish on the casting surface.
DRAFT — Taper allowed on the vertical faces of a pattern to permit removal of it from the sand mould without excessive rapping or tearing of the mould walls. DRAG — The lower or bottom section of a mould or pattern.
FEED HEAD — A reservoir of molten metal provided to compensate for contraction of metal as it solidifies, by the feeding down of liquid metal to prevent voids. They reduce shrinkage cracks and erosion of sand at sharp intersections.
FIN — A thin piece of metal projecting from a casting at the parting line or at the junction of the cores or of cores and mould etc. FLASH — Thin fin or web of metal extending from the casting along the joint line as a result of poor contact between cope and drag moulds. Cracks show up as fluorescent lines.