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Substance used for grinding, honing, lapping, superfinishing and polishing. Examples include garnet, emery, corundum, silicon carbide, cubic boron nitride and diamond in various grit sizes.

abrasive band

Endless band coated with diamond or other abrasive that is fitted to a special band machine for machining difficult-to-cut materials.

abrasive belt

Abrasive-coated belt used for production finishing, deburring and similar functions. See coated abrasive.

abrasive cutoff disc

Blade-like disc with abrasive particles that cuts/parts stock in a slicing motion.

abrasive cutoff machine

Machine that uses blade-like discs impregnated with abrasive particles to cut/part stock. See saw, sawing machine.

abrasive flow machining

Finishing and deburring operation for holes, inaccessible areas or restricted passages. Done by clamping the workpiece in a fixture, then extruding semisolid abrasive media through the passage. Often, multiple parts are loaded into a single fixture and finished simultaneously.

abrasive machining

Various grinding, honing, lapping and polishing operations that utilize abrasive particles to impart new shapes, improve finishes and part stock by removing metal or other material.

abrasive waterjet (AWJ)

System that uses high-pressure waterjets in combination with a slurry of fine abrasive grains to machine materials. See waterjet cutting.

abrasive-wire bandsawing

Variation of bandsawing that uses a small-diameter wire with diamond, cubic boron nitride or aluminum-oxide abrasives bonded to the surface as the cutting blade. Alternative to electrical-discharge machining for producing dies, stripper plates, electrodes and cams from difficult-to-machine conductive and nonconductive materials. See bandsawing.


Sulfur, chlorine and other materials added to cutting fluids to improve lubricity, stabilize oil emulsions and prevent chipwelding under high heat and pressure. See cutting fluid.


Mixture of concentrate and water prepared to restore depleted cutting fluid to its original state.

age hardening

Hardening of a heat-treated material that occurs slowly at room temperature and more rapidly at higher temperatures. Usually follows rapid cooling or cold working.

alloy steels

Steel containing specified quantities of alloying elements (other than carbon and the commonly accepted amounts of manganese, sulfur and phosphorus) added to cause changes in the metal’s mechanical and/or physical properties. Principal alloying elements are nickel, chromium, molybdenum and silicon. Some grades of alloy steels contain one or more of these elements: vanadium, boron, lead and copper.

alloying element

Element added to a metal to change its mechanical and/or physical properties.


Substances having metallic properties and being composed of two or more chemical elements of which at least one is a metal.

alpha iron

The body-centered cubic form of pure iron. Each of eight atoms is located in the corner of a cube, and one atom is located in the center of the cube. Alpha iron is stable below 1,670º F (910º C).


Formation of an aluminum or aluminum-alloy coating on a metal by hot dipping, hot spraying or diffusion.

aluminum alloys

Aluminum containing specified quantities of alloying elements added to obtain the necessary mechanical and physical properties. Aluminum alloys are divided into two categories: wrought compositions and casting compositions. Some compositions may contain up to 10 alloying elements, but only one or two are the main alloying elements, such as copper, manganese, silicon, magnesium, zinc or tin.

aluminum oxide

Aluminum oxide, also known as corundum, is used in grinding wheels. The chemical formula is Al2O3. Aluminum oxide is the base for ceramics, which are used in cutting tools for high-speed machining with light chip removal. Aluminum oxide is widely used as coating material applied to carbide substrates by chemical vapor deposition. Coated carbide inserts with Al2O3 layers withstand high cutting speeds, as well as abrasive and crater wear.


Not having a crystal structure; noncrystalline.

angle of entry

Determined by the position of the milling cutter’s centerline relative to the edge of the workpiece. Depending on the cutter diameter and the radial width of cut, the angle of entry can be negative or positive. A negative angle of entry occurs when the cutter’s centerline is located on the workpiece. Such an angle is recommended because the insert contacts the workpiece by its strong front rake, not by its weak cutting edge. To produce a negative angle of entry, the radial width of cut should exceed the cutter radius. A positive angle of entry occurs when the cutter’s centerline is not located on the workpiece. It happens when the radial width of cut is less than the cutter radius. A positive angle of entry should be avoided because the insert contacts the workpiece by its weakest part—the cutting edge.

angle plate

Solid adjustable or nonadjustable plate that holds work at a precise angle to the spindle during machining. Also used for inspection.


Softening a metal by heating it to and holding it at a controlled temperature, then cooling it at a controlled rate. Also performed to produce simultaneously desired changes in other properties or in the microstructure. The purposes of such changes include improvement of machinability, facilitation of cold work, improvement of mechanical or electrical properties and increase in stability of dimensions. Types of annealing include blue, black, box, bright, full, intermediate, isothermal, quench and recrystallization.

approach angle

Angle between the insert’s side-cutting edge and the line perpendicular to the milling cutter’s axis of rotation. Approach angle, which is also known as cutting edge angle, is used with metric units of measurement. See lead angle.

APT file

A file for automatically programmed tools that consists of the input language, an APT processor, an APT postprocessor and a computer of sufficient size to run the APT program. The APT system was initially developed for 3-, 4- and 5-axis milling machines, but because of further development, is capable of a range of applications, including point-to-point and turning work.


Shaft used for rotary support in machining applications. In grinding, the spindle for mounting the wheel; in milling and other cutting operations, the shaft for mounting the cutter.

arithmetic average (AA)

The mathematical expression denoting one of several parameters that describe surface texture (same as average roughness Ra). Average roughness is the arithmetic average height deviation of the measured surface profile from the profile centerline. See surface texture.


Joining together two or more parts to complete a structure.


Hot deformation of metastable austenite within controlled ranges of temperature and time that avoids formation of nonmartensitic transformation products.


Heat-treatment for ferrous alloys in which a part is quenched from the austenitizing temperature at a rate fast enough to avoid formation of ferrite or pearlite, and then held at the to achieve the desired characteristics. Austempering at lower temperatures (240° C to 270° C) produces a part with maximum strength, while austempering at higher temperatures (360° C to 380° C) yields high ductility and toughness.appropriate transformation temperature


Solid solution of one or more elements in face-centered cubic iron. Unless otherwise designated (such as nickel austenite), the solute is generally assumed to be carbon. Austenite can dissolve up to 2 percent carbon. Austenite is relatively soft, ductile and nonmagnetic.


Heating an alloy above its transformation temperature and then quenching it in a salt bath or other medium that extracts the heat at a sufficiently high rate to prevent formation of undesirable high-temperature-transformation qualities on its surface or in its microstructure. See austenite; martensite; martensiting.

automatic bar machine

Machine for turning bar stock. Similar to an automatic chucking machine, except that stock size is limited to through-the-spindle capacity and workpiece is held by push, draw or stationary collets rather than by chucks. See automatic chucking machine; turning machine.

automatic chucking machine

Machine with multiple chucks and toolholding spindles that permits processing of several parts simultaneously or multiple machining steps in one pass through the machine. See automatic bar machine.

automatic screw machine

Turning machine designed to produce parts automatically from coil or bar stock. The two basic types are cam (mechanical) and programmable (computer-controlled). Usually single-spindle, but Swiss types often have multiple spindles. See lathe; turning machine.

automatic toolchanger

Mechanism typically included in a machining center that, on the appropriate command, removes one cutting tool from the spindle nose and replaces it with another. The changer restores the used tool to the magazine and selects and withdraws the next desired tool from the storage magazine. The changer is controlled by a set of prerecorded/predetermined instructions associated with the part(s) to be produced.


Approach under which all or part of a machining or manufacturing process is accomplished by setting in motion a sequence that completes the process without further human intervention. May be mechanical (controlled by stops, cams, etc.), electrical (controlled by relays, contact switches, etc.) or electronic (computer- or microprocessor-controlled). “Fully automated” implies computer-integrated manufacturing. See CIM, computer-integrated manufacturing.

axial force

When drilling, a force that is directed axially—along the direction of machining. The magnitude of an axial force rises with the drill’s diameter and the chisel edge’s width. Axial force is also known as thrust. When turning and boring, the term “feed force” is commonly used instead of “axial force.” See cutting force.

axial rake

On angular tool flutes, the angle between the tooth face and the axial plane through the tool point.


Joint, rotational, directional or transversal movement of which the robot is capable. See degrees of freedom.