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Home > Glossary of Foundry Terms > M

Glossary of Foundry Terms - M

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The capability of being cut, turned, broached, etc., by machine tools.

Machine Allowance

Stock added to the part to permit machining of the part to final dimensions.

Machine Drawing

An engineering drawing which depicts the final size and shape of the part for its end use. See Computer Aided Design (CAD).

Machine Finish

Allowance of stock on the surface of the pattern to permit the machining of the casting to the required dimensions.


Trade name for a method of magnetic crack detection.


Trade name for a method of magnetic crack detection in which the magnetic particles are treated so that they fluoresce in ultraviolet light.

Magnetic Crack Detection

Method of locating cracks in materials which can be magnetized; done by applying magnetizing force and applying finely divided iron powder which then collects in the region of the crack.

Magnetic Particle Inspection

A nondestructive method of inspecting the surface integrity of ferromagnetic materials.


The property of being permanently deformed by compression without rupture.

Malleable Iron

Iron that may be altered in shape by hammering or by the pressure of rollers without exhibiting fracture or brittleness. The majority of the carbon content is in the form of graphite nodules rather than flakes. See Nodular Iron.


Annealing or heat-treating operation performed on white iron castings to transform the combined carbon into temper carbon.


One of the elements; its chemical symbol is Mn. It’s formula weight is 54.93; specific gravity 7.2, and melting point is 1260°C. Metallic manganese is used in the nonferrous industry both as a deoxidizing agent and as an essential constituent to improve physical properties of certain alloys.

Manganese Briquets

Crushed ferromanganese bonded with a special refractory in briquet form, and containing 2-lb metallic manganese and ½-lb metallic silicon.

Manganese Steel (Austenitic)

See Hadfield Manganese Steel.

Maraging Steel

A high alloyed steel that is hardened by both martensite transformation and by age hardening. See Age Hardening, Martensite.

Martempering (Interrupted Quenching)

A hardening treatment of a steel involving a slow cool through the martensitic transformation range to reduce stresses associated with the quenching of austenite. An important aspect of martempering is that no transformation product other than martensite should form. See Austenite, Martensite, Quenching.


A generic term used for microstructures formed by diffusionless phase transformations. A constituent found in hardened steel; has a needle like microstructure. See Mf, Ms.

Martensitic Stainless Steels

A corrosion-resistant ferrous alloy with a predominant martensitic phase.

Mass Effect

The effect that the mass of a component has on the properties of the material from which the part is made. In castings, such effects may arise due to the effect of mass on the solidification rate and on the rate of temperature change during heat treatment.

Master Pattern

An original pattern made to produce castings which are then used as metal patterns. See Casting.


A form of wood, plaster of Paris, sand or other material on which an irregular pattern is laid or supported while the drag is being rammed.


A metal or other plate on which patterns split along the parting line are mounted back to back with the gating system to form an integral piece.


Meallographic Structure

The nature, distribution, and amounts of the metallographic constituents in a metal.

Mechanical Properties

Those properties of a material that reveal the elastic and inelastic reaction when force is applied, or that involve the relationship between stress and strain; for example, the modulus of elasticity, tensile strength, and fatigue limit. This term should not be used interchangeably with "physical properties."

Melting Pot

Metal, graphite-clay, or ceramic vessel in which metal is melted.

Melting Range

Pure metals melt at one definite temperature, but constituents of alloys melt at different temperatures, and the variation from the lowest to the highest is called the melting range. See Alloy.

Melting Rate

Amount of metal melted in a given period of time, usually one hour.

Melting Zone

Portion of the cupola above the tuyeres in which the metal melts. See Cupola, Tuyeres.

Metal Lot

A master heat that has been approved for casting and given a sequential number by the foundry.

Metal Penetration

Defect in the casting surface which appears as if the metal has filled the voids between the sand grains without displacing them.


An element intermediate between metals and nonmetals possessing both metallic and nonmetallic properties, as arsenic, sometimes applied to elements commonly bonded in small amounts in steel, as carbon, manganese, boron, silicon, sulfur, and phosphorus.

Metallstatic Pressure

A compound phase referring to hydrostatic pressure, substituting "Metall" since "Hydro" connotes water.

Metallurgical Bond

The bond between two metals whose interface is free of voids, oxide films, or discontinuities.


Science dealing with the constitution, structure, and properties of metals and alloys, and the processes by which they are obtained from ore and adapted to the use of man.


A method of cold repair of castings and forgings.

Metals Comparator

An instrument for testing or identifying metallic and nonmetallic parts. Parts are placed in an electromagnetic field and a standard parts in a matched electromagnetic field. Distortions of the magnetic fields are compared on an oscilloscope.


A metal ceramic high in Cr-Al 2O3.

Metastable (Unstable)

A state of pseudo-equilibrium.

Mexico Bay Sand

A sand similar to Michigan City dune sand mined at Selkirk Beach, near Mexico, NY, on Lake Ontario. It has a silica content of 90% and over.

Meyer Hardness Test

A test to determine tendency of a metal to harden when deformed plastically. A series of indentations are made in the metal using a fixed-diameter ball and progressively increasing loads. See Brinell Hardness, Charpy Impact Test.



The temperature at which martensite formation finishes during cooling. See Martensite, Ms.

Mica Schist

A type of micaceous refractory rock used for lining cupolas and other melting furnaces.

Mica Strainer

A skim core made of thin mineral silicates crystallizing in monoclinic form.

Michigan Sand

Core sands of dune or lake sand and bank sands found in Michigan.

Micro Pipes (British) (Microshrinkage)

Tiny cavities, a fraction of a millimeter in diameter, with irregular outlines, which occur in castings. Etching shows they occur at intersections of convergent dendritic directions.

Microcast Process

A patented method of precision-casting alloys, as Vitallium, Monel, Inconel and the Haynes Stelite alloys. See Inconel, Monel.


Etching of metal samples for examination under the microscope.


A type of extensometer for measuring elongation of test piece in a tensile test.


Examination by means of a microscope.


The hardness of microconstituents of a material. See Hardness.


0.000001 (1/1,000,000th) of an inch. A common unit of measurement in surface measurement research and in standard roughness (surface) unit values of performance of machinery.


A test coupon used to give rapid indication of the effectiveness of magnesium treatment of ductile iron. See Ductile Iron.


Extremely fine porosity in castings caused by shrinkage or gas evolution and apparent on radiographic film as mottling. See Microshrinkage.


Process of passing x-rays through a thin section of an alloy in contact with photographic film, and then magnifying the radiograph 50 to 100 diameters to observe the distribution of alloying constituents, of voids, and of other microstructural features. See X-rays.


Minute object or structures which are invisible or not clearly distinguished without the use of a microscope.


A metal specimen whose surface has been polished and etched to reveal the microstructure. See Microstructure.


Very finely divided porosity resulting from interdendritic shrinkage resolved only by use of the microscope; may be visible on radiographic films as mottling. Etching shows they occur at intersections of convergent dendritic directions.


A method of identifying metallic constituents using spectrographic arc. See Spectography.


The structure and characteristic condition of metals as revealed on a ground and polished (etched or unetched) specimen at magnifications above 10 diameters. See Microsection.


A low load hardness tester, suitable for both Vickers and Knoop tests, working with loads of between 10 to 3000 grams. See Knoop Hardness, Vickers Diamond.

Microtone (British)

An instrument for cutting thin sections of soft specimens.

Migra Iron (British)

A special pig iron for high quality castings.



A low load hardness tester, suitable for both Vickers and Knoop tests, working with loads of between 10 to 3000 grams. See Knoop Hardness, Vickers Diamond.


Designation for the United States Government military standards, specifications, usually requiring rugged, exacting, testing equal to the exigencies of combat usage.

Mild Steel

Plain carbon steel of about 0.25% carbon or less.

Mill Sale

Iron oxide scale formed on steel during hot working processes, cooled in air.

Mill Stars

Multi-pointed white iron or hard iron bodies used in a Tumbling Barrel to assist in polishing and cleaning.


Removing metal with a milling cutter.

Milliroentgen (mr)

A sub-multiple of the roentgen equal to one-thousandth (1/1000th) of a roentgen.

Milliscope (British)

An instrument which gives an electrical warning when melt reaches a predetermined temperature.


Natural inorganic substance which is either definite in chemical composition and physical characteristics or any chemical element or compound occurring naturally as a product of inorganic processes.


Alloy of rare-earth metals containing about 50% cerium and 50% lanthanum, neodymium, and similar elements.


Solubility; ability of two or more liquids to form a homogeneous solution.


Denotes an irregularity of the casting surface caused by incomplete filling of the mold due to low pouring temperature, gas back-pressure from inadequate venting of the mod, and inadequate gating.

Mitis Casting

Casting of very mold steel.


A full-size model built accurately for study, testing or display.


A proportional representation of an object in any scale.

Modell Number

A value giving a measure of wear resistance.


A process in which the eutectic temperature, structure, and composition of aluminum-silicon alloys are apparently altered by the addition of small amounts of a third element, such as sodium. A similar phenomenon can be effected by chill casting.

Modulus Of Elasticity (E)

In tension it is the ration of stress to the corresponding strain within the limit of elasticity (Yield Point) of a material. For carbon and low alloy steels any composition and treatment, the value is approximately 30,000,000 psi.

Modulus of Resilience ( ur )

The amount of strain energy per unit volume required to tress a material from zero to the yield stress limit. The modulus of resilience is proportional to the area under the elastic portion of the stress-strain diagram. Units are Pa or psi.

Modulus of Rigidity

In a torsion test the ratio of the unit shear stress to the displacement caused by it per unit length in the elastic range. See Shear Modulus.

Modulus of Rupture

Used in both bending and torsion testing. In bending, the modulus of rupture is the bending moment at fracture divided by the section modulus. In torsion, modulus of rupture is the torque at fracture divided by the polar section modulus.

Modulus of Toughness (ut)

Amount of work per unit volume of a material required to carry that material to failure under static loading. Equal to the area under the entire stress-strain curve. Units are Pa or psi.



Equipment for sealing by vacuum impregnation of small pores in castings. See Porosity.

Moh's Scale

A scratch hardness test for determining comparative harness using ten standard minerals, from talc to diamond.

Moisture Content

The amount of water contained in a substance that can be driven off by heating at 220°F - 230°F (104.4°C - 110°C).

Moisture Teller

A patented apparatus for the rapid determination of moisture content of molding sand.

Molasses Water

A solution of water and molasses sprayed on sand molds to strengthen mold surface and yield a fine finish layer. See Sand Molding.


Normally consists of a top and bottom form, made of sand, metal, or any other investment material which contains the cavity into which molten metal is poured to produce a casting of definite shape and outline. See Mold Cavity.

Mold Blower

Molding equipment for blowing sand mixture onto the pattern with compressed air; allows for faster production than gravity rollover dump.

Mold Board (Follow Board)

The board upon which the pattern is placed to make the mold.

Mold Cavity

The impression in a mold produced by removal of the pattern. It is filled with molten metal to form the casting. Gates and risers are not considered part of the mold cavity. See Casting, Gates, Risers.

Mold Coating

Coating to prevent surface defects, i.e., metal penetration and improve casting finish. See Core Wash.

Mold Conveyor

Power-driven unit on which molds are conveyed from the molding station to pouring station to shakeout.

Mold Cover Half (Cover Die)

The top half of the mold, the cope. In die casting, the front half of the die, which remains stationary as the die is opened. See Cope.

Mold Facing

See Mold Coating.

Mold Hardener

In sand molds in which sodium silicate is the binder, injection of CO2 causes a chemical reaction which results in a rigid structure.

Mold Jacket

A wooden or metal form slipped over a mold to support the side during pouring.

Mold Oven

Oven or furnace in which molds are dried.

Mold Shift

Casting defect resulting when the two cavities in the cope and drag molds do not match properly. See Cavity, Mold Cavity, Cope, Drag.

Mold Wash

Usually an aqueous emulsion, containing various organic or inorganic compounds or both, which is used to coat the face of a mold cavity. Materials include graphite, silica flour, etc. This guards against penetration of metal into sand walls.

Mold Weights

Weights placed on top of molds to offset internal or ferrostatic pressure.



Ability of sand to flow into a flask and around a pattern measured in the amount of sand falling through an inclined screen or slot. See Flask, Pattern.

Moldabilty Controller

A patented device for controlling water additions to sand mix to maintain a consistent moldability index.

Molding Bench

The making of sand molds from loose or production patterns at a bench.

Molding Floor

Making sand molds from loose or production patterns at a floor. Patterns are usually too large to be handled satisfactorily on the bench. See Sand Molding, Molding Sand.

Molding Gravel

The coarser and more permeable grades of molding sand generally used in production casting of exceptional size and weight.

Molding Machine

Hand or pneumatically operated machine on which molds are made and which rams the sand by squeezing or jolting or both.

Molding Material

A material suitable for making molds into which molten metal can be cast.

Molding Sand

Mixture of sand and clay suitable for mold making.

Molding Sand Mixture

A sand mixture suitable for making molds into which molten metal can be cast.

Molding Sands

Sands containing over 5% natural clay, usually between 8 and 20%. See Naturally Bonded Molding Sand.

Molding, Bench

Making sand molds by hand tamping loose or production patterns at a bench without assistance of air or hydraulic action.

Molding, Floor

Making sand molds from loose or production patterns of such size that they cannot be satisfactorily handled on a bench or molding machine, the equipment being located on the floor during the entire operation of making the mold.

Molding, Machine

Making sand molds from production patterns on molding machines. See Sand Molding.

Molding, Pit

Molding method in which the drag is made in a pit or hole in the floor. See Drag.

Molecular Weight

Weight of the smallest quantity of a substance processing all its normal physical properties.


The smallest particle of a substance that can exist in the free state and which has the same composition as any larger mass of the substance.


A metal used widely in alloying of other metals. It is used as hardening element for steel, and for diecasting dies. The melting point is 2,620°C (4,748°F), and the atomic number is 42.

Molybdic Oxide

The oxide of molybdenum; added to the furnace in briquetted form as an important finishing constituent in nitriding steels.


A high nickel alloy, approximately 67% Ni, 28% Cu, the balance Fe, Mn, Si and other elements. Monel metal is resistant to corrosion and is widely used to resist the action of acids. See Inconel.



Periodic or continuous determination of the does rate in an occupied area (area monitoring) or the does received by a person. See Monitoring, Personnel.

Monitoring, Personnel

Monitoring any part of any individual, his breath, or excretions, or any part of his clothing.

Monitoring Area

Routine monitoring of the level of radiation or of radioactive contamination of any particular area, building, room or equipment. Usage in some laboratories or operation distinguishes between routine monitoring and survey activities.

Monkey Cooler (British)

In a blast furnace, the smaller of a series of three water coolers protecting the cinder notch. The largest is the cooler, while the in-between cooler is the intermediate cooler.

Monocast Process

A patented application of resin-bonded sand to line the flask in the production of centrifugal cast pipe. The resin-bonded layer is thinner than the conventional sand lining. See Flask.


An isothermal reversible reaction in a binary system, in which a liquid on cooling, decomposes into a solid and a second liquid of different composition. Compare with Eutectic.


An instrument for measuring indentation hardness. It is fitted with two dials, one to measure depth of penetration, the other the load.


A very plastic clay, more siliceous than kaolinite; the principal constituent of bentonite. See Bentonite.

Moore, R. R., Fatigue Machine

A constant load rotating bending type fatigue testing machine.

Moisture, Workable

That range of moisture content within which sand fills, rams, draws, and dries to a satisfactory mold, and within which the sand does not dry out too fast to mold and patch.

Mother Metal

The molten alloy just before final solidification and freezing out of the solid. See Alloy, Solidification.

Motorized Variac

An autotransformer for stepless voltage control in shell molding.



White iron structure interspersed with spots or flecks of gray.

Mottled Cast Iron

Iron which consists of a mixture of variable proportions of gray iron and white cast iron. Mottle cast ironhas a mottled fracture. See Gray Iron, White Cast Iron.

Mould (British)

Normally consists of a top and bottom form, made of sand, metal, or any other investment material which contains the cavity into which molten metal is poured to produce a casting of definite shape and outline. The American spelling of this word is "mold". See Mold.

Mould Cavity (British)

The impression in a mould produced by removal of the pattern. It is filled with molten metal to form the casting. Gates and risers are not considered part of the mould cavity. See Mold Cavity.

Mould Coating (British)

Coating to prevent surface defects and improve surface finish. See Mold Coating.


Abbreviation for melting point.


The temperature at which transformation of austenite to martensite starts during cooling.


A term frequently used to designate plastic lining materials. See Daubing.

Mud daub

See Daubing.

Muffle Furnace (Kiln)

A furnace in which the heating is indirect; the material to be heated is contained in a refractory container heated from the outside.

Muliductor Power Source

A device to convert standard 3-phase, 60 cycle current to single- phase, 180-cycle current, so-called medium frequency; produces a strong, controlled stirring action for induction melting.


Type of foundry-sand-mixing machine. See Foundry Sand.


The thorough mixing of sand, water and binding ingredients to form tempered ready-to-use molding or core sand. See Core Sand.

Mulling and Tempering

The thorough mixing of sand with a binder, either natural or added, with lubricant of other fluid, as water.

Multiple Mold

Composite mold made up of stacked sections. Each section produces a complete gate of castings. All castings are poured from a central downgate.

Multiple-Cavity Die

A die-casting die having more than one impression of the same part. See Combination Die.

Mushet Steel

An air hardened steel containing about 2% C, 2% Mn, and 7% W, developed by Scotsman Robert Musket in 1870.

Mushy Stage

The state between sold and liquid in alloys which freeze over a wide range of temperatures.


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Atlas Foundry Company, Inc.
601 N. Henderson Avenue
Marion, IN 46952-3348
Telephone: (765) 662-2525 • Fax: (765) 662-2902
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