C Is for Caliper

Metalworking Glossary for the Letter C

See the index to the Glossaries here:

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• C-Frame Milling Machine. A large, hydraulically powered mill used in industrial production. C-frame mills get their name from the configuration of the head, column and table looking like a letter “C.”
• CAD. The abbreviation for computer-aided design, a CAD program allows a user to digitally design a part that can be entered into a CNC machine to be milled, 3D printed, or otherwise created.
• Caliper. A caliper is a device used to measure a dimension on an object. Calipers have been in use since at least the sixth century BC, and while analog versions are still widely used, digital calipers are often chosen for their accuracy and ease of operation. A common type of caliper is the vernier caliper, which has a large set of moveable jaws for measuring external dimensions, a smaller set for measuring internal dimensions of a hollow or hole, and a sliding vernier scale that moves along the longer main scale.
• Cam. A device used to convert rotary motion into an irregular rotary motion or a reciprocating motion. It consists of a rotating or sliding piece in a mechanical linkage and usually operates by striking a lever at one or more points in an eccentric circular path.
• CAM. The abbreviation for computer-aided machining or manufacturing, a CAM program takes a CAD file and allows a user to create tool paths to cut the design using a CNC machine.
• Camber. The term camber refers to a slight curving or arching of a surface. In band sawing, camber means a deviation from the straightness of the blade. A positive camber is a curvature in the direction of the teeth, while a negative camber is a curvature away from the teeth.
• Capacity. The maximum work a machine tool or metal fabrication machine can perform, based on its size, strength, and other factors. For example, capacity can be measured in the length of a workpiece that can be accommodated by a shear or a lathe, or in the tonnage that can be exerted on a workpiece by a press brake.
• Capstan Lathe. Similar in style to a turret lathe, a capstan lathe is a lightweight lathe that features a hexagonal turret tool head in place of the tailstock.
• Carbide Tool Bits. Carbide is an alloy of carbon and another element that has similar or lower electronegativity, such as silicon or tungsten. The alloying process makes certain types of carbide very hard, such as tungsten carbide, which is three times more ridged than steel. Because of its hardness, tool bits composed of carbide—or coated with it—are ideal for use in machining hard materials.
• Carbon Steel. Steel that contains up to 1.2% of carbon with only residual amounts of alloying elements. Mild steel is a low carbon steel containing less than 0.3% carbon and is very malleable, making it ideal for fabrication work.
• Carbon Steel Blade. A bandsaw blade made from carbon steel with teeth that have been hardened to a greater extent than the rest of the blade.
• Carriage. The carriage of a lathe holds the tool bit and guides it into position to cut or otherwise manipulate the workpiece. It moves between the headstock and the tailstock and includes several components, such as the apron, the compound rest, the saddle, and the toolpost. 
• Case Hardening. A process, usually involving heat treatment, that makes the surface layer of a ferrous alloy substantially harder and more wear-resistant than the core, which remains softer, yet tougher.
• Casting. The process of pouring molten metal into a mold where it is allowed to solidify. Also, the part made through this process.
• CAT Scanner. Abbreviation for “computed axial tomography” scanner, an older term for a CT scanner.
• Cavity. In forging, cavity refers to the hollow impression in a die.
• Center Lathe. Another name for an engine lathe.
• Center. A point or axis around which something revolves or rotates. In reference to lathes, a center, or “lathe center,” is a tool that has a sharp point on one end to position a workpiece accurately on the axis of the lathe’s main spindle.
• Centered Grinder. A style of cylindrical grinder that fixtures the workpiece on an axis between two spindles while it is being ground.
• Centering Lathe. A centering lathe is a dual head machine that drills a hole in the center of each end of a workpiece to be used in later operations.
• Centerless Grinder. A style of cylindrical grinder which uses two rotary wheels, one of which is driven, to secure a workpiece in place between them on a work rest.
• Centrifugal Casting. A casting process that involves pouring molten metal into a rotating mold.
• Ceramic Cutter. A cutting tool made from a ceramic like aluminum oxide, silicon nitride, or silicon carbide. Ceramic cutters have much greater heat resistance, allowing them to be used in high-speed operations (as much as 20 times faster than a solid carbide cutter is able).
• Chamfering. Creating a symmetrical sloping edge by cutting away a 90° corner. The lathe function of chamfering or “chamfer turning” creates a diagonal transition between two surfaces with different diameters. It is like step turning, but with an angle instead of a square 90° transition between the surfaces. In forging, the term chamfer means to break, grind or otherwise remove sharp edges from forging stock.
• Chatter. A noise that occurs during a cutting operation due to vibrations caused by issues like an improperly mounted tool or workpiece, an incorrect speed, or a dull tool. Chatter is usually an indication of a problem that should be investigated and corrected to avoid possible tool breakage, machine damage, or an improper finish on a part.
• Chip Flow. The direction and angle of chip evacuation from a cutter in a machining operation. The direction of chip flow is controlled by the back rake angle of the cutting tool and is a critical factor in tooling selection. Chip flow is an important factor to consider in a machining operation, as it can affect surface finish, power consumption, and other productivity issues. 
• Chip Load. A measurement of the thickness of the chips removed by each cutting edge during a machining operation. Machinists will optimize chip load through adjustments of the feed rate and cutting speed to increase the efficiency of the operation.
• Chip Pan. Chip pans collect chips and waste fluids from a lathe, saw or another machine tool for disposal.
• Chip Weld. The fusing of a chip (or part of a chip) to a tooth face on a saw blade, caused by elevated temperatures and extreme pressure.
• Chips. Another name for swarf, the byproduct of a milling, cutting, turning or other machine tool operation.
• Chisel. A common tool of the blacksmith that is made of high carbon steel. While the cutting edge of a chisel is hardened and tempered, the head on the other end is left semi-malleable so that it doesn’t crack when hammered.
• Chop. A die forging defect, referring to metal sheared from a vertical surface and spread by a die over an adjoining horizontal surface.
• Chrome Plating. The process of depositing a thin layer of chromium onto a metal component for protective or decorative purposes.
• Chuck. Chucks are attachments for the main spindle of a lathe or other machine that hold the workpiece in position.
• Chuckers. Chuckers, automatic chuckers, and automatic chucking machines are names for large capacity multi-spindle lathes.
• Clearance. The amount of distance by which the surface of one object can pass by the surface of another. Clearance can also be measured by an angle.
• Clearance Angle. The degree of inclination of the rear surface of a cutting tool from the surface of the workpiece as measured from the point of contact. It eliminates interference between the cutting tool and the workpiece. Clearance angle directly influences surface quality and accuracy and is always a positive value—it can’t be zero or negative. It usually ranges between +3° to +15°. Clearance angle must have a positive value. It cannot be negative or zero. 
• Climb Milling. A way of milling in which the cutter rotates in the same direction as the feed of the worktable, as opposed to conventional milling, where the cutter rotates against the direction of the feed. The workpiece tends to be pulled into the cutter in climb milling, lowering power consumption and decreasing feed forces.
• Close-tolerance Forging. A forging process held to closer than normal tolerances to eliminate most or all the normal post-forging machining. Also known as precision forging.
• CMM. An abbreviation for coordinate measuring machine.
• CNC Grinding System. A highly advanced type of tool and cutter grinder used for crafting precision parts for high-tech industries, such as aerospace, automotive, and medical products.
• CNC Lathe. A CNC lathe, often called a CNC turning center, uses a computer numerical control to program toolpaths for highly accurate and repeatable operations.
• CNC Milling Machine. A multi-axis mill controlled by a programmable computer numeric control (CNC).
• CNC. Abbreviation for computer numeric control. It is a computerized control device on a machine tool or piece of fabrication equipment that allows a program to be manually entered or uploaded into the machine to automatically produce a part when run. Most CNC devices can store programs in a library for future use.
• Coal Forge. Also known as a coke forge or a charcoal forge, it uses coal or another fuel to heat metal, controlling the process by altering the volume of the fuel that is used, the shape of the fuel or fire, and the amount of air that is introduced.
• Coarse Pitch Milling Cutter. A differential-pitched cutter containing only a small number of inserts, ideal for unstable milling operations where lower cutting forces are recommended. Also known as a low-density cutter.
• Coating. Tool coatings increase the life of a tool beyond what the material of the tool can provide. For example, a titanium aluminum nitride (TiAlN) coating on a tool like an end mill would be used to keep a soft metal like aluminum from sticking to it, while polycrystalline diamond (PCD) is a hard coating for cutters that need to withstand high wear.
• Cog. A tooth in the rim of a gear wheel.
• Cogging. An operation in which an ingot is worked into a billet or bloom using a forging hammer or a forging press.
• Coining. Coining is a metal-bending process used in press brakes that employs the same high tonnage to form the metal as a coining press would use, hence the name. Like bottom bending, coining pushes the metal to the bottom of the press brake die, but then compresses it so that it conforms to the exact angle of the tooling. This extreme pressure changes the molecular structure of the workpiece, eliminating almost all springback.
• Cold Rolled Steel. Also known as cold form steel or cold drawn steel, it refers to steel that has gone through hot rolling, followed by an additional finishing process once it has cooled, such as drawing, grinding, or turning. The further processing gives the steel an improved surface finish and can increase its strength.
• Cold Saw. A cold saw is a type of metal-cutting saw that utilizes a disc-like sawblade. Unlike a chop saw that creates extreme heat while wearing down a workpiece, a cold saw transfers heat from the saw blade to the chips that are expelled. This ability to dissipate heat and keep the blade and workpiece cool is where the saw gets its name.
• Cold Trimming. Removing excess metal from a forging that is at room temperature.
• Cold Working. As opposed to hot working or warm forging, cold working is the manipulation of metal without heating it to create a permanent plastic deformation of the material at a temperature low enough to produce strain hardening. Cold working is also known as cold forging and cold forming.
• Collet. A small, precision type of chuck formed from a segmented collar which put around a cylindrical object such as a cutter shaft that centers and securely clamps the object when tightened.
• Column. On a mill, the column—or “mill column”—is mounted on the base and houses some of the drive components, as well as supporting the head, knee, and other parts of the machine.
• Column Milling Machine. Another name for a knee mill. It can be a vertical or a horizontal mill.
• Combination Lathe. Sometimes called a 3-in-1 machine, a combination lathe combines a lathe with a mill and/or a drill press in a single machine tool and is designed for hobbyists.
• Combination Square. A tool used in for drafting and layout that combines a square with a level, a protractor, and a center head.
• Comparator. A shortened term usually referring to an optical comparator.
• Compound Rest. The compound rest, also called the top slide, is the uppermost part of a lathe carriage and is usually where the tool post is mounted. It is attached to the cross-slide and provides a limited amount of movement for precise angle positioning of the tool.
• Computed Tomography Scanner. Usually known by the shorter CT scanner (and often CAT scanner, for computed axial tomography), a computed tomography scanner uses an x-ray procedure to create cross-sectional images with the help of computer processing. A 3D model can be created using the CT images, but unlike the standard 3D optical scans, they can show the inner details of the object.
• Computer Numeric Control. Commonly just abbreviated as “CNC,” a computer numeric control is a device for running a program on a machine to automatically produce a part when run.
• Concentricity. The relationship between two diameters.
• Contour. The outline of an object’s surface.
• Contour Comparator. Another name for an optical comparator.
• Contour Gauge. Another name for a profile gauge, a group of parallel pins that can move independently in a framework to make an impression of a surface.
• Contour Shaper. A shaper that is fitted with a tracer mechanism that follows a template to copy a similar contour into the workpiece.
• Contour turning. Contouring or contour turning is a lathe function that creates curving contours of a predefined geometry in a spinning workpiece, usually over multiple passes.
• Conventional EDM Machine. A popular type of electrical discharge machine because of its ability to create complex profiles in metal. A previously machined shape, often made of graphite or copper, becomes the tool (the top electrode). It is moved vertically down towards the workpiece (the bottom electrode) through a dielectric fluid and a negative impression in the shape of the tool is then eroded away from the workpiece by the several hundred thousand sparks that are generated per second. Other names for conventional type EDM machines are Cavity-type, Die Sinker, Ram, Sinker, and Volume EDMs.
• Conventional Milling. A way of milling in which the cutter rotates against the direction of the feed of the worktable, as opposed to climb milling, where the cutter rotates in the same direction as the feed. The cutter pushes against the workpiece in conventional milling, increasing both power consumption and feed forces.
• Coolant. A liquid, gas, or compound used to reduce or regulate temperature during an operation that generates heat. Coolant helps increase tool life and improve the surface finish of the workpiece. In metal sawing, coolant is another name for cutting fluid.
• Coordinate Measuring Machine. A coordinate measuring machine, or CMM for short, is a machine that senses distinct points on the surface of an object with a probe using light, touch, a laser, or some other means. The data collected is assembled to measure the geometry of the object. One type of a portable CMM is called a laser scanning arm.
• Corrosion. A chemical change in a material because of its interaction with its surroundings. With metals, corrosion is usually considered a deterioration of the material that damages the surface. It is a natural process that converts a refined metal into something that is more chemically stable, like a carbonate, oxide, hydroxide, or sulfide. A frequent corrosion of iron and iron alloys (like steel) is oxidation, usually manifested as rust. Oxidation occurs when iron alloys are exposed to oxygen and water for a long period of time. Other metals corrode in other ways, such as copper tarnishing.
• Cover. A cover on a machine tool or piece of metal fabrication equipment may be for user protection, decoration, or a combination of the two. On a press brake, for example, any side or back covers usually have a primary purpose of safety, to keep operators and onlookers from getting too close to moving parts, while the common hydraulic cylinder covers on the front of a brake are strictly for aesthetic purposes.
• Crank Shaper. The most common type of shaper, named after its type of drive mechanism, and features a quick return mechanism.
• Creep Feed Grinder. A machine that can remove a large amount of material—up to a full depth of cut—usually in a single pass. Both cylindrical grinders and surface grinders can be designed as creep feed grinders.
• Critical Point. The temperature at which recrystallization or another phase change takes place in a metal.
• Cross Feed. A feeding mechanism in machining that moves at a right angle to the main feed on a machine.
• Cross Section. A view showing the internal structure of a workpiece or other object as it would be seen if the object were cut through on a specific plane.
• Cross-slide. The cross-slide is part of a lathe carriage at the top of the lathe and allows the tool bit to move back and forth towards the workpiece.
• Crucible. A container used for melting metals.
• Crucible Steel. High-grade tool steel produced by melting the specific metals in a crucible.
• Crude Iron. A product which is obtained by smelting iron ore. It has a very high carbon content and is often called by the colloquial name “pig iron.”
• CT Scanner. Abbreviation for computed tomography scanner.
• Cup Grinder. Another name for a vertical spindle surface grinder.
• Cutting. Cutting, in metalworking, is the severing or piercing of a piece of metal. Shears, saws, plasma cutters, lasers, grinders, and other machines can cut metal. As a lathe function, cutting involves positioning a tool bit against a rotating cylindrical workpiece to remove a significant amount of material.
• Cutting Fluid. A liquid used with a saw or other cutting machine to lubricate the cutting process, flush swarf, and reduce heat. Because of its properties allowing the dissipation of heat, it is often called coolant.
• Cutting Rate. Another term for cutting speed, measuring the amount of material cut per minute.
• Cutting Speed. The speed at which a cutting tool moves in relation to a workpiece. It can be the surface speed of the tool itself (in the case of a rotating milling tool or a spinning saw blade) or the speed of the workpiece (in the case of a spinning workpiece mounted in a lathe). In the United States it is usually designated in feet per minute (FPM), then converted to revolutions per minute (RPM) for setting the controls of the machine tool.
• Cutting Tool. Interchangeable tooling made from a hardened piece of metal or ceramic that is machined and ground to have cutting edges so that it can be used in a cutting operation with a workpiece composed of a softer material.
• Cyaniding. A method of case hardening steel by heating it in molten cyanide.
• Cycle Time. The total operational time it takes to produce one part on a machine.
• Cycloidal Gear. A type of spur gear with a specific type of rounded curve to the teeth.
• Cylindrical Grinder. A grinder that is usually used for shaping the outside of a workpiece that is capable of being rotated through a central axis. The workpiece and the grinding wheel both must be simultaneously rotated.