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Checking measuring instruments and devices against a master set to ensure that, over time, they have remained dimensionally stable and nominally accurate.

cam-actuated assembly

Assembly machine, rotary or linear, utilizing cam mechanisms to orient and/or assemble parts.

cam-cutting attachment

Device for cutting face, peripheral or cylindrical cams from flat cam-former stock.

canned cycle (fixed cycle)

Subroutine or full set of programmed NC or CNC steps initiated by a single command. Operations are done in a set order; the beginning condition is returned to when the cycle is completed. See CNC, computer numerical control; NC, numerical control.


Compound of carbon and one or more metallic elements. For cutting tools, tungsten carbide, titanium carbide, tantalum carbide or a combination of these in a cobalt or nickel matrix provides hardness, wear resistance and heat resistance. Other elements added to carbide include vanadium, niobium, silicon, boron and hafnium.

carbon steels

Known as unalloyed steels and plain carbon steels. Contains, in addition to iron and carbon, manganese, phosphorus and sulfur. Characterized as low carbon, medium carbon, high carbon and free machining.


Casehardening metal by heating it in a mixture of carbon and nitrogen and by controlling the cooling rate. Allows carbon to enter the surface microstructure.


Absorption and diffusion of carbon into solid ferrous alloys by heating, to a temperature above the transformation range, in contact with a suitable carbonaceous material. A form of casehardening that produces a carbon gradient extending inward from the surface, enabling the surface layer to be hardened either by quenching directly from the carburizing temperature or by cooling to room temperature, then reaustenitizing and quenching.

carriage stop

Mechanical device placed on the lathe head or ways to prevent over-travel that might damage the machine or workpiece.


Generic term covering several processes applicable to steel that change the chemical composition of the surface layer by absorption of carbon, nitrogen or a mixture of the two and, by diffusion, create a concentration gradient. Processes commonly used are carburizing, quench hardening, cyaniding, nitriding and carbonitriding.

cast alloys

Alloys cast from the molten state. Most high-speed steel is melted in an electric-arc furnace and cast into ingots.

cast cobalt-base alloys

Used as wear-resistant (largest application area), corrosion-resistant and heat-resistant materials. They have different names depending on the manufacturers, such as Stellite, Tribaloy, Haynes alloys and MP35N. These alloys are hard, brittle and difficult to use for making cutting tools.

cast irons

Cast ferrous alloys containing carbon in excess of solubility in austenite that exists in the alloy at the eutectic temperature. Cast irons include gray cast iron, white cast iron, malleable cast iron and ductile, or nodular, cast iron. The word “cast” is often left out.

cavity cutting

Machining entirely within the body of a workpiece.

cavity type laser machining

Process that removes material by focusing a concentrated laser beam onto the workpiece. The material is melted and vaporized. In the cavity process, the beam is carefully controlled to prevent burning through the workpiece.

cell manufacturing

Grouping processes, equipment and people together to manufacture a specific family of parts. Highly automated and able to changeover quickly to produce a different part within the family of parts. See family of parts.

cemented carbides

Typical powder-metallurgical products. They are sintered compounds of cobalt (or another binder metal) and carbides of refractory metals suitable for use as a cutting tool material. The majority of metalcutting indexable inserts are multicarbide compounds of tungsten carbide, titanium carbide, tantalum carbide and/or niobium carbide with cobalt as a binder metal.


Compound of iron and carbon known as iron carbide and having the approximate chemical formula Fe3C. It is characterized by an orthorhombic crystal structure. Cementite contains 6.67 percent carbon. When it occurs as a phase in steel, the chemical composition is altered by the presence of manganese and other carbide-forming elements. Cementite is hard and brittle. It is magnetic below 1,670º F (910º C).

center drill

Drill used to make mounting holes for workpiece to be held between centers. Also used to predrill holes for subsequent drilling operations. See centers.

center drilling

Drilling tapered holes for mounting workpiece between centers. Center-drilled holes also serve as starter holes for drilling larger holes in the same location. See centers; drilling.

center rest

Support provided at the center of the working area of a cylindrical grinder to prevent part deflection during grinding.


1. Process of locating the center of a workpiece to be mounted on centers. 2. Process of mounting the workpiece concentric to the machine spindle. See centers.

centerless grinding

Grinding operation in which the workpiece rests on a knife-edge support, rotates through contact with a regulating or feed wheel and is ground by a grinding wheel. This method allows grinding long, thin parts without steady rests; also lessens taper problems. Opposite of cylindrical grinding. See cylindrical grinding; grinding.


Cone-shaped pins that support a workpiece by one or two ends during machining. The centers fit into holes drilled in the workpiece ends. Centers that turn with the workpiece are called “live” centers; those that do not are called “dead” centers.

centrifugal feeder (rotary feeder)

Utilizes centrifugal force to continuously orient and deliver parts, at a specified feed rate, to an assembly machine.


Filtering device that uses a spinning bowl and the differences in specific gravities of materials to separate one from another. A centrifuge can be used to separate loosely emulsified and free oils from water-diluted metalworking fluid mixes and to remove metalworking fluids from chips.


Cutting tool materials based on aluminum oxide and silicon nitride. Ceramic tools can withstand higher cutting speeds than cemented carbide tools when machining hardened steels, cast irons and high-temperature alloys.


Cutting tool materials based mostly on titanium carbonitride with nickel and/or cobalt binder. Cermets are characterized by high wear resistance due to their chemical and thermal stability. Cermets are able to hold a sharp edge at high cutting speeds and temperatures, which results in exceptional surface finish when machining most types of steels.


Machining a bevel on a workpiece or tool; improves a tool’s entrance into the cut.

chamfering tool

Cutter or wheel that creates a beveled edge on a tool or workpiece.

Charpy test

Impact test in which a V-notched, keyhole-notched or U-notched specimen, supported at both ends, is struck behind the notch by a striker mounted at the lower end of a bar that can swing as a pendulum. The energy absorbed in fracture is calculated from the height to which the striker would have risen if there had been no specimen, and the height to which it actually rises after fracture of the specimen. See Izod test.


Condition of vibration involving the machine, workpiece and cutting tool. Once this condition arises, it is often self-sustaining until the problem is corrected. Chatter can be identified when lines or grooves appear at regular intervals in the workpiece. These lines or grooves are caused by the teeth of the cutter as they vibrate in and out of the workpiece and their spacing depends on the frequency of vibration.

chemical vapor deposition (CVD)

High-temperature (1,000° C or higher), atmosphere-controlled process in which a chemical reaction is induced for the purpose of depositing a coating 2µm to 12µm thick on a tool’s surface. See coated tools; PVD, physical vapor deposition.


Small piece of material removed from a workpiece by a cutting tool or grinding wheel.

chip clearance

In milling, the groove or space provided in the cutter body that allows chips to be formed by the inserts.


Groove or other tool geometry that breaks chips into small fragments as they come off the workpiece. Designed to prevent chips from becoming so long that they are difficult to control, catch in turning parts and cause safety problems.


Surface treatment at elevated temperature, generally carried out in a pack, vapor or salt bath, in which an alloy is formed by the inward diffusion of chromium into the base metal.


Workholding device that affixes to a mill, lathe or drill-press spindle. It holds a tool or workpiece by one end, allowing it to be rotated. May also be fitted to the machine table to hold a workpiece. Two or more adjustable jaws actually hold the tool or part. May be actuated manually, pneumatically, hydraulically or electrically. See collet.

circular saw

Cutoff machine utilizing a circular blade with serrated teeth. See saw, sawing machine.

circular-saw blade

Cutting tool for a cold or circular saw. Blade is round with serrated cutting teeth.


Space provided behind a tool’s land or relief to prevent rubbing and subsequent premature deterioration of the tool. See land; relief.

climb milling (down milling)

Rotation of a milling tool in the same direction as the feed at the point of contact. Chips are cut to maximum thickness at the initial engagement of the cutter’s teeth with the workpiece and decrease in thickness at the end of engagement. See conventional milling.

closed-loop system

CNC system in which the program output, or the distance the slide moves, is measured and compared to the program input. The system automatically adjusts the output to be the same as the input.

coated abrasive

Flexible-backed abrasive. Grit is attached to paper, fiber, cloth or film. Types include sheets, belts, flap wheels and discs.

coated tools

Carbide and high-speed-steel tools coated with thin layers of aluminum oxide, titanium carbide, titanium nitride, hafnium nitride or other compounds. Coating improves a tool’s resistance to wear, allows higher machining speeds and imparts better finishes. See CVD, chemical vapor deposition; PVD, physical vapor deposition.

cold working

Deforming metal plastically under conditions of temperature and strain rate that induce strain hardening. Working below the recrystallization temperature, which is usually, but not necessarily, above room temperature.


Flexible-sided device that secures a tool or workpiece. Similar in function to a chuck, but can accommodate only a narrow size range. Typically provides greater gripping force and precision than a chuck. See chuck.

commercial-grade tool steel

Low-grade tool steel; not controlled for hardenability.

compacted graphite iron

Cast iron having a graphite shape intermediate between the flake form typical of gray cast iron and the spherical form of fully spherulitic ductile cast iron. Also known as CG iron, CGI or vermicular iron, it is produced in a manner similar to that of ductile cast iron but using a technique that inhibits the formation of fully spherulitic graphite nodules.


Materials composed of different elements, with one element normally embedded in another, held together by a compatible binder.

computer numerical control (CNC)

Microprocessor-based controller dedicated to a machine tool that permits the creation or modification of parts. Programmed numerical control activates the machine’s servos and spindle drives and controls the various machining operations. See DNC, direct numerical control; NC, numerical control.

computer-aided design (CAD)

Product-design functions performed with the help of computers and special software.

computer-aided engineering (CAE)

Engineering functions performed with the help of computers and special software. Includes functions such as determining a material’s ability to withstand stresses.

computer-aided manufacturing (CAM)

Use of computers to control machining and manufacturing processes.

computer-integrated manufacturing (CIM)

Theoretically, an approach under which all phases of production—including management, sales, order processing, design, quality control and chipmaking—are controlled or monitored by interconnected computers. Practically, a term applied to systems approximating the ideal.


Agents and additives that, when added to water, create a cutting fluid. See cutting fluid.

continuous casting

Casting technique in which a cast shape is continuously withdrawn through the bottom of the mold as it solidifies, so that its length is not determined by mold dimensions. Used chiefly to produce semifinished mill products such as billets, blooms, ingots, slabs and tubes.

contouring attachment

Handwheel-operated mechanism for holding and guiding the workpiece while sawing contours on a contour bandsaw.

conventional milling (up milling)

Cutter rotation is opposite that of the feed at the point of contact. Chips are cut at minimal thickness at the initial engagement of the cutter’s teeth with the workpiece and increase to a maximum thickness at the end of engagement. See climb milling.

conversational programming

Method for using plain English to produce G-code file without knowing G-code in order to program CNC machines.


Fluid that reduces temperature buildup at the tool/workpiece interface during machining. Normally takes the form of a liquid such as soluble or chemical mixtures (semisynthetic, synthetic) but can be pressurized air or other gas. Because of water’s ability to absorb great quantities of heat, it is widely used as a coolant and vehicle for various cutting compounds, with the water-to-compound ratio varying with the machining task. See cutting fluid; semisynthetic cutting fluid; soluble-oil cutting fluid; synthetic cutting fluid.


Process of reducing the heat content of a tool, part, assembly or material. Cooling may be required for a variety of reasons: to improve tool life, increase cutting speeds and ensure workpiece tolerances by controlling expansion. When heat-treating metal parts, part of the process is cooling, either by air, water or oil.

copper alloys

Copper containing specified quantities of alloying elements added to obtain the necessary mechanical and physical properties. The most common copper alloys are divided into six groups, and each group contains one of the following major alloying elements: brasses—major alloying element is zinc; phosphor bronzes—major alloying element is tin; aluminum bronzes—major alloying element is aluminum; silicon bronzes—major alloying element is silicon; copper-nickels and nickel-silvers—major alloying element is nickel; and dilute-copper or high-copper alloys, which contain small amounts of various elements such as beryllium, cadmium, chromium or iron.


Chemical or electrochemical reaction between a material, usually a metal, and its environment that produces a deterioration of the material and its properties.

corrosion fatigue

Process in which a metal fractures prematurely under conditions of simultaneous corrosion and repeated cyclic loading at lower stress levels or fewer cycles than would be required in the absence of the corrosive environment.

corrosion resistance

Ability of an alloy or material to withstand rust and corrosion. These are properties fostered by nickel and chromium in alloys such as stainless steel.


Use of weights or mechanisms to balance a workpiece, grinding wheel, rotating tool or other device. Minimizes machining vibration and maximizes cutting force.


Tool, guided by a pilot, that expands a hole to a certain depth.


Enlarging one end of a drilled hole. The enlarged hole, which is concentric with the original hole, is flat on the bottom. Counterboring is used primarily to set bolt heads and nuts below the workpiece surface.


Tool that cuts a sloped depression at the top of a hole to permit a screw head or other object to rest flush with the surface of the workpiece.


Cutting a beveled edge at the entrance of a hole so a screw head sits flush with the workpiece surface.


Depressions formed on the face of a cutting tool caused by heat, pressure and the motion of chips moving across the tool’s surface.

creep-feed grinding

Grinding operation in which the grinding wheel is slowly fed into the workpiece at sufficient depth of cut to accomplish in one pass what otherwise would require repeated passes. See grinding.

crush grinding

Method of producing intricate forms in a part by using a grinding wheel dressed to the shape of the form desired. See grinding.

cubic boron nitride (CBN)

Crystal manufactured from boron nitride under high pressure and temperature. Used to cut hard-to-machine ferrous and nickel-base materials up to 70 HRC. Second hardest material after diamond. See superabrasive tools.

curtain application

Arrangement of multiple nozzles that apply fluid to a broad cutting area, as is found on a horizontal, post-type band machine or a large hacksaw.


Step that prepares a slug, blank or other workpiece for machining or other processing by separating it from the original stock. Performed on lathes, chucking machines, automatic screw machines and other turning machines. Also performed on milling machines, machining centers with slitting saws and sawing machines with cold (circular) saws, hacksaws, bandsaws or abrasive cutoff saws. See saw, sawing machine; turning.

cutoff blade

Blade mounted on a shank or arbor and held in a milling-machine spindle for simple cutoff tasks.

cutoff wheel

Rotating cutting wheel that cuts bar stock, pipe, etc., to a desired length.

cutter compensation

Feature that allows the operator to compensate for tool diameter, length, deflection and radius during a programmed machining cycle.

cutting fluid

Liquid used to improve workpiece machinability, enhance tool life, flush out chips and machining debris, and cool the workpiece and tool. Three basic types are: straight oils; soluble oils, which emulsify in water; and synthetic fluids, which are water-based chemical solutions having no oil. See coolant; semisynthetic cutting fluid; soluble-oil cutting fluid; synthetic cutting fluid.

cutting force

Engagement of a tool’s cutting edge with a workpiece generates a cutting force. Such a cutting force combines tangential, feed and radial forces, which can be measured by a dynamometer. Of the three cutting force components, tangential force is the greatest. Tangential force generates torque and accounts for more than 95 percent of the machining power. See dynamometer.

cutting speed

Tangential velocity on the surface of the tool or workpiece at the cutting interface. The formula for cutting speed (sfm) is tool diameter 5 0.26 5 spindle speed (rpm). The formula for feed per tooth (fpt) is table feed (ipm)/number of flutes/spindle speed (rpm). The formula for spindle speed (rpm) is cutting speed (sfm) 5 3.82/tool diameter. The formula for table feed (ipm) is feed per tooth (ftp) 5 number of tool flutes 5 spindle speed (rpm).

cutting tool materials

Cutting tool materials include cemented carbides, ceramics, cermets, polycrystalline diamond, polycrystalline cubic boron nitride, some grades of tool steels and high-speed steels. See HSS, high-speed steels; PCBN, polycrystalline cubic boron nitride; PCD, polycrystalline diamond.


Casehardening method that introduces carbon and nitrogen to the workpiece simultaneously.

cylindrical grinding

Grinding operation in which the workpiece is rotated around a fixed axis while the grinding wheel is fed into the outside surface in controlled relation to the axis of rotation. The workpiece is usually cylindrical, but it may be tapered or curvilinear in profile. See centerless grinding; grinding.

cylindrical-grinding attachment

Device that mounts to the table of a surface grinder or lathe, permitting both straight and tapered grinding of round stock.