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Strip or block of precision-ground stock used to elevate a workpiece, while keeping it parallel to the worktable, to prevent cutter/table contact.

parametric-based CAD/CAM

Model features can be driven by rules or parameters set up by the user. They can be dimensions, geometric constraints (tangent, concentric, co-linear, etc.), equations and design tables, among others.

part orientation

Designing the assembly machine, feeding mechanism and the part itself so the parts to be assembled are properly aligned prior to and during the assembly operation.


When used in lathe or screw-machine operations, this process separates a completed part from chuck-held or collet-fed stock by means of a very narrow, flat-end cutting, or parting, tool.

parts feeder

Mechanism that delivers parts to the assembly machine at a specified rate and with proper orientation.

payload (workload)

Maximum load that the robot can handle safely.


Lamellar aggregate of ferrite and cementite in slowly cooled iron-carbon alloys occurring normally as a principle constituent of steel and cast iron. Fully annealed steel containing 0.85 percent carbon consists entirely of pearlite.


Mechanical working of a metal by hammer blows or shot impingement.

peripheral milling

Form of milling that produces a finished surface generally in a plane parallel to the rotating axis of a cutter having teeth or inserts on the periphery of the cutter body. See milling.

phase transformation

Heat generated by machining action that causes changes in the workpiece’s surface layers. This can result in softer- or harder-than-desired workpiece surfaces, as well as undesirable changes in cutting tools.

photochemical machining

Variation on chemical machining that uses a chemically resistant mask that is sensitive to light. Light activates the mask only in the areas to be protected. The remaining mask is washed away. The process is typically used to produce parts such as circuit boards and other delicate items.

physical vapor deposition (PVD)

Tool-coating process performed at low temperature (500° C), compared to chemical vapor deposition (1,000° C). Employs electric field to generate necessary heat for depositing coating on a tool’s surface. See CVD, chemical vapor deposition.

pick-and-place robot

Simple robot or piece of hard automation that is capable of the simple actions of picking an object from a fixed point and placing the object at another fixed point.


1. On a saw blade, the number of teeth per inch. 2. In threading, the number of threads per inch.


Localized corrosion of a metal surface, confined to a point or small area, that takes the form of cavities.


Machining operation that creates flat surfaces. The workpiece is reciprocated in a linear motion against one or more single-point tools. Also used to create contours or irregular configurations.

planing bit

Cutting tool similar in appearance to a turning tool but with a longer shank.

planing machine (planer)

Machines flat surfaces. Planers take a variety of forms: double-housing, open-side, convertible and adjustable open-side, double-cut and milling. Large multihead (milling, boring, drilling, etc.) planers and planer-type milling machines handle most planing work.

plastic deformation

Permanent (inelastic) distortion of metals under applied stresses that strain the material beyond its elastic limit.

plastic stereolithography

Process that uses a combination of lasers and photosensitive, liquid plastics to generate models. The desired workpiece is electronically “sliced” into thin sections. The laser beam scans over a bath of uncured polymer and only turns on where material should exist, duplicating the sliced section. The polymer partially hardens in these areas. By lowering the workpiece into the polymer bath and scanning successive layers, the part is developed. When the part is completely built up, it is removed from the bath and finish-cured with intense ultraviolet light. Can be used to generate complex models.

plunge milling

Highly productive method of metal removal in which an axial machining operation is performed in a single tool sequence. The tool makes a series of overlapping, drill-like plunges to remove part of a cylindrical plug of material one after another. Because of the increased rigidity of a Z-axis move, the tool can cover a large cross-section of material.

plunge turning

Form of hard turning that uses the entire cutting edge or a portion of the cutting edge to create an orthogonal cut.

point angle

Included angle at the point of a twist drill or similar tool; for general-purpose tools, the point angle is typically 118°.

point-to-point system

NC system normally used for drilling and other operations where center-point location is readily determined. Tool is rapidly moved to a position, then drills, taps, reams, bores, counterbores, countersinks or performs some other task.

polar additives

Animal, vegetable or synthetic oil that, when added to a mineral oil, improves its ability to penetrate the tool/workpiece interface.


Abrasive process that improves surface finish and blends contours. Abrasive particles attached to a flexible backing abrade the workpiece.

polishing attachment

Abrasive grinding device that mounts on a contour bandsaw and uses fine-grit belts to grind and polish.

polycrystalline cubic boron nitride (PCBN)

Cutting tool material consisting of polycrystalline cubic boron nitride with a metallic or ceramic binder. PCBN is available either as a tip brazed to a carbide insert carrier or as a solid insert. Primarily used for cutting hardened ferrous alloys.

polycrystalline diamond (PCD)

Cutting tool material consisting of natural or synthetic diamond crystals bonded together under high pressure at elevated temperatures. PCD is available as a tip brazed to a carbide insert carrier. Used for machining nonferrous alloys and nonmetallic materials at high cutting speeds.

powder metallurgy

Processes in which metallic particles are fused under various combinations of heat and pressure to create solid metals.

power brushing

Any process that uses a power-driven, rotating industrial brush to deburr, clean or finish a metal part. Depending on the application, the brush fibers, collectively known as brush fill material, may be metal wires; fiberglass-coated, abrasive-filled plastics; synthetics such as nylon and polypropylene; natural animal hairs such as horsehair; or vegetable fibers such as tampico and bahia.

power hacksaw

Machine fitted with serrated blade held taut in a reciprocating frame that cuts in one direction, either on the forward or return stroke. See saw, sawing machine.

power hacksawing

Sawing process that uses the back-and-forth motion of a short, straight-toothed blade to cut the workpiece. Hacksawing machines are generally electrically driven and may or may not provide for application of cutting fluid to the saw blade or workpiece.

precision machining (precision measurement)

Machining and measuring to exacting standards. Four basic considerations are: dimensions, or geometrical characteristics such as lengths, angles and diameters of which the sizes are numerically specified; limits, or the maximum and minimum sizes permissible for a specified dimension; tolerances, or the total permissible variations in size; and allowances, or the prescribed differences in dimensions between mating parts.


Heating before some further thermal or mechanical treatment.

probability theory

Discipline based on the likelihood of any given event happening; mathematical techniques built around sampling methods, combinations and permutations. Key to understanding statistical-process-control systems. See SPC, statistical process control.

process annealing

Imprecise term denoting various treatments used to improve workability. For the term to be meaningful, the condition of the material and the time-temperature cycle used must be stated.

process control

Method of monitoring a process. Relates to electronic hardware and instrumentation used in automated process control. See in-process gaging, inspection; SPC, statistical process control.


Measure of the efficiency with which human and material resources are used to produce goods and services. Output per man-hour has traditionally been the most stable measure, but, since direct labor is sharply reduced by CAD, CAM and computer-integrated manufacturing, alternative methods of measuring may be more accurate. Software and other support/service functions must be factored into the equation.


Machining vertical edges of workpieces having irregular contours; normally performed with an endmill in a vertical spindle on a milling machine or with a profiler, following a pattern. See mill, milling machine.