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M-code programming

Miscellaneous, or auxiliary, functions constitute on/off type commands. Used to control actions such as starting and stopping of motors, turning coolant on and off, changing tools, and clamping and unclamping workpieces.


The relative ease of machining metals and alloys.

machinability rating

A relative measure of the machinability of a metallic work material under specified standard conditions. Machinability rating is expressed in percents, with the assumption that the machinability rating of AISI 1212 free-machining steel is 100 percent. If machinability ratings of work materials are less than 100 percent, it means that such work materials are more difficult to machine than AISI 1212 steel; and vice versa if machinability ratings are greater than that for AISI 1212 steel.


Process of giving a workpiece a new configuration by cutting or shaping it. Typically performed on a machine tool or machining center. Includes cutting and shaping all kinds of materials, not just metals. Generally associated with precision and high-quality fit. See metalcutting, material cutting; metalforming; metalworking.

machining center

CNC machine tool capable of drilling, reaming, tapping, milling and boring. Normally comes with an automatic toolchanger. See automatic toolchanger.

magnetic chuck

Workholding device used on surface grinders and milling machines for holding ferrous parts with large, flat sides. Holding power may be provided by permanent magnets or by an electromagnetic system. See chuck.

magnetic-particle inspection

Nondestructive method of inspection for determining the existence and extent of surface cracks and similar imperfections in ferromagnetic materials. Finely divided magnetic particles, applied to the magnetized part, are attracted to and outline the pattern of any magnetic-leakage fields created by discontinuities.

malleable cast iron

Cast iron made by prolonged annealing of white cast iron in which decarburization and/or graphitization take place to eliminate some or all of the cementite. The graphite is in the form of temper carbon. There are ferritic and perlitic malleable cast irons. Their typical composition ranges are: 2.2 to 2.9 percent carbon, 0.2 to 1.3 percent manganese, 0.9 to 1.9 percent silicon, 0.05 to 0.18 percent sulfur and 0.18 percent (maximum) phosphorus.


Workholder for turning that fits inside hollow workpieces. Types available include expanding, pin and threaded.


Arm or basic object-transferring device. Hands or gripping devices vary according to application, as do arm design and number of joints (axes or degrees of freedom). See degrees of freedom; effectuating device.

manufacturing resources planning

Management method, normally computer-aided, for cost-effective control of manufacturing support functions, such as inventory, production equipment and personnel. MRP was the initial, somewhat limited method; MRP-II implies a more sophisticated system.

maraging steels

Nickel in the amount of 18.5 percent is the principal alloying element in the maraging steels. Other alloying elements are cobalt, molybdenum, aluminum and titanium. With a maximum carbon content of 0.030 percent, these steels are essentially carbon-free. They utilize the soft, ductile, iron-nickel martensite, which can be age-hardened by additions of other alloying elements. The most common maraging steel grades are 18Ni(200), 18Ni(250), 18Ni(300) and 18Ni(350). The numerical designations represent ultimate tensile strength of these grades. Maraging steels are used in the aerospace industry and for making tools (various dies, trim knives and springs).


1. Hardening procedure in which an austenitized ferrous workpiece is quenched in a medium whose temperature is maintained substantially at the Ms temperature (temperature at which martensite starts to form from austenite) of the workpiece. It is held in the medium until its temperature is uniform throughout—but not long enough to permit bainite to form—and then cooled in air. The treatment is frequently followed by tempering. 2. When the process is applied to carburized (casehardened) material, the controlling Ms temperature is that of the case. This variation of the process is frequently called marquenching.


Formed during rapid cooling of austenite at the temperature rate higher than 500º F (260º C) per second. Such rapid cooling causes restructuring of crystalline lattice of gamma iron into crystalline lattice of alpha iron in which carbon is fully dissolved. Because only 0.04 percent carbon can be dissolved in alpha iron, the excessive amount of carbon transforms into supersaturated solution of carbon in alpha iron. This type of solution is called martensite, which is characterized by an angular needlelike brittle structure and high hardness (greater than 60 HRC).


Rapid quenching of carbon steel in the austenite state causes a new structure—martensite—to form. Martensite is extremely hard. See austenite; austenitizing; martensite.

material safety data sheet (MSDS)

Form containing safety, regulatory, physical and other pertinent information regarding a chemical.

materials handling

Methods, equipment and systems for conveying materials to various machines and processing areas and for transferring finished parts to assembly, packaging and shipping areas.

mechanical properties

Properties of a material that reveal its elastic and inelastic behavior when force is applied, thereby indicating its suitability for mechanical applications; for example, modulus of elasticity, tensile strength, elongation, hardness and fatigue limit.

medium-carbon steels

Group of carbon steels designated by American Iron and Steel Institute numerical classification as AISI 1029, 1030, 1034, etc., up to AISI 1053, for a total of 16 grades. They are often selected where higher strength is required. Most commonly used steels for machined components. Composition of medium-carbon steels is: 0.25 to 0.55 percent carbon, 0.30 to 1.00 percent manganese, 0.040 percent (maximum) phosphorus and 0.050 percent (maximum) sulfur. See high-carbon steels; low-carbon steels.

metal stereolithography

Process similar to plastic stereolithography but uses powder metal to build up the part. See stereolithography, plastic.

metal-removal factor

Volume of metal removed per unit of power in a given period of time (reciprocal of the specific power-consumption factor). Also known as the K-factor. Metal-removal factor depends on the depth of cut and feed rate. Increases in depth of cut and feed rate increases K-factor; decreases in depth of cut and in feed rate decrease K-factor.

metal-removal rate

Rate at which metal is removed from an unfinished part, measured in cubic inches or cubic centimeters per minute.

metalcutting (material cutting)

Any machining process used to part metal or other material or give a workpiece a new configuration. Conventionally applies to machining operations in which a cutting tool mechanically removes material in the form of chips; applies to any process in which metal or material is removed to create new shapes. See metalforming.


Manufacturing processes in which products are given new shapes either by casting or by some form of mechanical deformation, such as forging, stamping, bending and spinning. Some processes, such as stamping, may use dies or tools with cutting edges to cut as well as form parts.


Any manufacturing process in which metal is processed or machined such that the workpiece is given a new shape. Broadly defined, the term includes processes such as design and layout, heat-treating, material handling and inspection.


Science of measurement; the principles on which precision machining, quality control and inspection are based. See precision machining, measurement.


Hardness of a material as determined by forcing an indenter such as a Vickers or Knoop indenter into the surface of the material under very light load; usually, the indentations are so small that they must be measured with a microscope. Capable of determining hardness of different microconstituents within a structure or measuring steep hardness gradients such as those encountered in casehardening.


A precision instrument with a spindle moved by a finely threaded screw that is used for measuring thickness and short lengths.


Measure of length that is equal to one-millionth of a meter.


Cutting small or thin parts from a larger base part. Uses a special machine with a thin, tensioned blade that takes a minimum kerf. Process for cutting expensive materials such as silicon, germanium and other computer-chip materials.


Structure of a metal as revealed by microscopic examination of the etched surface of a polished specimen.


Machining operation in which metal or other material is removed by applying power to a rotating cutter. In vertical milling, the cutting tool is mounted vertically on the spindle. In horizontal milling, the cutting tool is mounted horizontally, either directly on the spindle or on an arbor. Horizontal milling is further broken down into conventional milling, where the cutter rotates opposite the direction of feed, or “up” into the workpiece; and climb milling, where the cutter rotates in the direction of feed, or “down” into the workpiece. Milling operations include plane or surface milling, endmilling, facemilling, angle milling, form milling and profiling.

milling arbor

Shaft or toolholder that inserts in the machine spindle and holds a peripheral-milling or facemilling cutter.

milling cutter

Loosely, any milling tool. Horizontal cutters take the form of plain milling cutters, plain spiral-tooth cutters, helical cutters, side-milling cutters, staggered-tooth side-milling cutters, facemilling cutters, angular cutters, double-angle cutters, convex and concave form-milling cutters, straddle-sprocket cutters, spur-gear cutters, corner-rounding cutters and slitting saws. Vertical cutters use shank-mounted cutting tools, including endmills, T-slot cutters, Woodruff keyseat cutters and dovetail cutters; these may also be used on horizontal mills. See milling.

milling machine (mill)

Runs endmills and arbor-mounted milling cutters. Features include a head with a spindle that drives the cutters; a column, knee and table that provide motion in the three Cartesian axes; and a base that supports the components and houses the cutting-fluid pump and reservoir. The work is mounted on the table and fed into the rotating cutter or endmill to accomplish the milling steps; vertical milling machines also feed endmills into the work by means of a spindle-mounted quill. Models range from small manual machines to big bed-type and duplex mills. All take one of three basic forms: vertical, horizontal or convertible horizontal/vertical. Vertical machines may be knee-type (the table is mounted on a knee that can be elevated) or bed-type (the table is securely supported and only moves horizontally). In general, horizontal machines are bigger and more powerful, while vertical machines are lighter but more versatile and easier to set up and operate.

minimum-quantity lubrication

Use of cutting fluids of only a minute amount—typically at a flow rate of 50 to 500 ml/hr.—which is about three to four orders of magnitude lower than the amount commonly used in flood cooling. The concept addresses the issues of environmental intrusiveness and occupational hazards associated with the airborne cutting fluid particles on factory shop floors. The minimization of cutting fluid also saves lubricant costs and the cleaning cycle time for workpieces, tooling and machines. Sometimes referred to as “near-dry lubrication” or “microlubrication.”


Ability of a liquid to mix with another liquid. See emulsion.

mist application

Atomized fluid generally applied when a clear view of the cut point is needed, as in contour bandsawing or manual milling. The airborne mist can be directed precisely to the point of cut, sometimes reaching areas flood-applied coolant cannot penetrate. The water evaporates on contact, providing further cooling, and leaves oils and additives on the work. See flood application.

mixture ratio

Ratio of water to concentrate in certain cutting fluids. See semisynthetic cutting fluid; soluble-oil cutting fluid; synthetic cutting fluid.

modular design (modular construction)

Manufacturing of a product in subassemblies that permits fast and simple replacement of defective assemblies and tailoring of the product for different purposes. See interchangeable parts.

modular fixturing

System in which fixtures are constructed from standardized, reusable components. Fixtures are assembled and disassembled quickly. Basic styles are subplate, dowel-pin and T-slot. See fixture; modular tooling.

modular robot

Robot with interchangeable components, such as gripping hands, that permit quick modification to suit a specific purpose.

modular tooling

1. Tooling system comprised of standardized tools and toolholders. 2. Devices that allow rapid mounting and replacement of tools. Commonly used with carousel toolchangers and other computerized machining operations. See toolchanger; toolholder.

modulus of elasticity

Measure of rigidity or stiffness of a metal, defined as a ratio of stress, below the proportional limit, to the corresponding strain. Also known as Young’s modulus.

modulus of rigidity

Ratio of shear stress to the corresponding shear strain for shear stress below the proportional limit of the material. Also known as shear modulus. MRP, MRP-II, materials requirements planning,

multifunction machines (multitasking machines)

Machines and machining/turning centers capable of performing a variety of tasks, including milling, drilling, grinding boring, turning and cutoff, usually in just one setup.