Glossary

Flat surface, usually at right angles and adjacent to the ground hole.

Flat, round workholder with slots used to hold regular- or irregular-shaped stock. If stock is markedly asymmetrical, counterbalances may be needed to prevent vibration.

Milling cutter for cutting flat surfaces.

Form of milling that produces a flat surface generally at right angles to the rotating axis of a cutter having teeth or inserts both on its periphery and on its end face.

Preliminary “cleanup” operation that provides a true reference surface before beginning another operation.

Parts grouped by shape and size for efficient manufacturing.

Phenomenon leading to fracture under repeated or fluctuating stresses having a maximum value less than the tensile strength of the material. Fatigue fractures are progressive, beginning as minute cracks that grow under the action of the fluctuating stress.

Number of cycles of stress that can be sustained prior to failure under a stated test condition.

Ability of a tool or component to be flexed repeatedly without cracking. Important for bandsaw-blade backing.

Maximum stress that can be sustained for a specified number of cycles without failure, the stress being completely reversed within each cycle unless otherwise stated.

Very fine or thin burr.

Same as a feather burr, except that feather edge can also refer to a very thin machined ridge located at the ends of a lead-in or lead-out thread. It is sometimes called a wire-edge or whisker-type burr.

Construction methodology. It means the model is constructed using 3-D objects (features), as opposed to individual lines, arcs, splines and surfaces.

Rate of change of position of the tool as a whole, relative to the workpiece while cutting.

Solid solution of one or more elements in body-centered cubic iron. Unless otherwise designated, for instance, as chromium ferrite, the solute is generally assumed to be carbon. On an equilibrium diagram, there are two ferrite regions separated by an austenite area. The lower area is alpha ferrite and the upper area is delta ferrite. If there is no designation, alpha ferrite is assumed. Not more than 0.04 percent carbon can be dissolved in alpha iron. Ferrite is stable below 1,670º F (910º C); it is soft, highly ductile, and magnetic. Ferrite loses its magnetic property above 1,414º F (768º C).

Segmented files mounted on an endless band for use on a powered band-type filing machine or on a contour band machine with a filing attachment.

Operation in which a tool with numerous small teeth is applied manually to round off sharp corners and shoulders and remove burrs and nicks. Although often a manual operation, filing on a power filer or contour band machine with a special filing attachment can be an intermediate step in machining low-volume or one-of-a-kind parts.

Mounts on a contour bandsaw for power-filing operations.

Rounded corner or arc that blends together two intersecting curves or lines. In three dimensions, a fillet surface is a transition surface that blends together two surfaces.

Relative ability of a fluid to form a film between workpiece and tool, under the influence of temperature and pressure, to prevent metal-to-metal contact. See lubricity.

Final cut made on a workpiece to generate final dimensions or specified finish. Often made using reduced feeds and higher speeds. Generally, the better the surface finish required, the longer the finish cut takes. Also, the final cut taken on an electrical-discharge-machined part.

Feeding in small increments for finishing the part.

Any of many different processes employed for surface, edge and corner preparation, as well as conditioning, cleaning and coating. In machining, usually constitutes a final operation.

Tool, belt, wheel or other cutting implement that completes the final, precision machining step/cut on a workpiece. Often takes the form of a grinding, honing, lapping or polishing tool. See roughing cutter.

Device, often made in-house, that holds a specific workpiece. See jig; modular fixturing.

Hardening process in which an intense flame is applied to the surfaces of hardenable ferrous alloys, heating the surface layers above the upper transformation temperature, whereupon the workpiece is immediately quenched.

Reduction in clearance on the tool’s flank caused by contact with the workpiece. Ultimately causes tool failure.

Thin web or film of metal on a casting that occurs at die partings and around air vents and movable cores. This excess metal is due to necessary working and operating clearances in a die. Flash also is the excess material squeezed out of the cavity as a compression mold closes or as pressure is applied to the cavity.

Flat surface machined into the shank of a cutting tool for enhanced holding of the tool.

System that can be programmed to assemble a family or group of similar assemblies. This typically is done with programmable robots. This system is contrasted to dedicated or fixed assembly systems.

Automated manufacturing system designed to machine a variety of similar parts. System is designed to minimize production changeover time. Computers link machine tools with the workhandling system and peripherals. Also associated with machine tools grouped in cells for efficient production. See cell manufacturing.

Fluid applied in volume by means of a recirculating system composed of a reservoir, filters, chip-removal components, pump, hoses and positionable application nozzles, along with movable splash shields, valves for adjusting flow and other controls. Fluids normally permit the highest metal-removal rates possible.

Uniaxial true stress at the onset of plastic deformation in a metal.

Unintentional surface irregularities that occur at infrequent or varying intervals, such as cracks, blowholes, checks, ridges and scratches. The effect of flows is not included in roughness average measurement. See lay; roughness; waviness.

Hand-operated hose and nozzle added to machine’s cutting-fluid-application system to permit manual flushing of table and workpiece areas.

Grooves and spaces in the body of a tool that permit chip removal from, and cutting-fluid application to, the point of cut.

Cutting straight or spiral grooves in drills, endmills, reamers and taps to improve cutting action and remove chips.

Rotary cutting tool employing one or more single-point tools for plane surfacing.

Workpiece rest or supporting device attached to the carriage that “follows” the cutting tool, keeping support near the point of cut. See steady rest.

Cutter shaped to cut stepped, angular or irregular forms in the workpiece. The cutting-edge contour corresponds to the workpiece shape required. The cutter can often be reground repeatedly without changing the cutting-edge shape. Two general classes: straight and circular.

Used to roll splines, gears, worms and threads. Cold-forming machine for production processing of previously machined parts. See broaching machine.

1. Maximum principal true stress at fracture. Usually refers to unnotched tensile specimens. 2. True stress (hypothetically) that will cause fracture without further deformation at any given strain.

Critical value (KIC) of stress intensity. A material property.

Group of carbon steels designated by the American Iron and Steel Institute numerical classification are free machining grades: AISI 1108, 1109, 1110, etc., up to AISI 1151 for a total of 14 grades. AISI 1211, 1212, 1213, 1215 and 12L14 carbon steels are also free machining grades. Free machining steels contain one or more additives, which enhance machining characteristics and lower machining cost. Increased sulfur content (from 0.20 to 0.33 percent in some grades) improves chip control. Addition of lead (from 0.15 to 0.35 percent in some grades) reduces friction and buildup of heat between the cutting edge of the tool and the workpiece.

Characteristic of abrasive grains that describes their tendency to fracture or break apart when hit or placed under pressure. Highly friable abrasives cut more easily, but wear faster than other abrasives. Friable abrasives are usually used on soft, gummy materials or where heat produced by worn grits must be carefully controlled. Friability is usually related to the levels of impurities in the manufactured abrasive mineral.

Sawing with a special band machine capable of achieving band velocities of 15,000 sfm or more. Metal removal is accomplished in two steps: Frictional heat softens the metal, then the teeth scoop out the molten material. Carbon-steel bands are used for flexibility and to maximize band life. Excellent for cutting extremely hard alloys but cannot be used on most aluminum alloys or other materials that load the teeth of conventional blades. See sawing.

Imprecise term that denotes an annealing cycle designed to produce minimum strength and hardness. For the term to be meaningful, the composition and starting condition of the material and the time-temperature cycle used must be stated.

Additive to cutting fluids to inhibit fungi. See bactericide.