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PAD. The general term used for that part of a die which delivers holding pressure to the metal being worked.
PART-REVOLUTION CLUTCH. A type of clutch that may be engaged or disengaged during any part of the cycle.
PEARLITE. The lamellar aggregate of ferrite and carbide. Note: It is recommended that this word be reserved for the microstructures consisting of thin plates or lamellae - that is, those that may have a pearly luster in white light. The lamellae can be very thin and resolvable only with, the best microscopic equipment and technique.
PERFORATING. The punching of many holes, usually identical and arranged in a regular pattern, in a sheet, workpiece blank, or previously formed part. The holes are usually round, but may be any shape. The operation is also called multiple punching. (See PIERCING.)
PIERCING. The general term for cutting (shearing or punching) openings, such as holes and slots in sheet material, plate, or parts. This operation is similar to blanking; the difference being that the slug or piece produced by piercing is scrap, whereas the blank produced by blanking is the useful part.
PILOT. Bullet-nosed component used in dies to maintain correct position of advancing strip. As the strip advances through a sequence of operations, the pilot entry into prepunched holes ensures precise registration of the part at each station of the strip.
PINCH POINT. Any point, other than the point of operation, at which it is possible for a part of the human body to be caught between the moving parts of a press or auxiliary equipment, between moving and stationary parts of a press or auxiliary equipment, or between the material and moving part or parts of the press or auxiliary equipment. (Explanation: The expression pinch point, as used in the standard, refers only to parts of the machine or parts associated with it that create a hazard. The expression is not used to describe hazards caused by the tooling at the point of operation, since these hazards are a different problem and require different treatment.)
PLASTIC ANISOTROPY. Directional difference in mechanical properties relative to rolling direction applied in producing the sheet metal.
PLASTIC DEFORMATION. Permanent distortion of a material under the action of applied stresses.
PLASTIC FLOW. The phenomenon that takes place when metals or other substances are stretched or compressed permanently without rupture.
PLASTICITY. That property or characteristic which permits substances to undergo permanent change in shape without rupturing. Practically, it is the property possessed by useful materials that permits stretching or compressing them into useful shapes.
PLATEN. The sliding member, slide, or ram of a hydraulic press.
PNEUMATIC TOGGLE LINKS. Special main links of a toggle press which are equipped with pneumatic cushions and a linkage to give air pressure controlled flexibility. These links compensate for variations in material thickness under the blankholder and also can be adjusted to exert different pressures at different corners of the blankholder.
POINT OF OPERATION. The area of the press in which material is actually positioned and work is being performed during any process, such as shearing, punching, forming, or drawing.
POISSON'S RATIO. The ratio of the lateral expansion to the longitudinal contraction under a compressive load, or the ratio of the lateral contraction to the longitudinal expansion under a tensile load, provided the elastic limit is not exceeded.
PREFORMED PART. A partially formed part which will be subjected to one or more subsequent forming operations.
PRESS. A machine tool having a stationary bed and a slide or ram that has reciprocating motion at right angles to the bed surface, the slide being guided in the frame of the machine.
PRESS BRAKE. (See BENDING BRAKE.)
PRESS FORGING. The forging process in which metal stock is formed between dies, usually by hydraulic pressure. Press forging is an operation that employs a single, slow stroke.
PRESS FORMING. Any forming operation performed with tooling by means of a mechanical or hydraulic press.
PROGRAMMABLE GAGING. Back-gaging in which the gage bar is driven by an encoder signal or servomotor that can be programmed by the operator.
PROGRESSION. The constant dimension between adjacent stations in a progressive die. As such, it is the precise distance the strip must advance between successive cycles of the press. Accuracy of the progression is guaranteed by piloting and by the feed unit.
PROGESSIVE DIE. A die with two or more stations arranged in line for performing two or more operations on a part, one operation usually being performed at each station.
PUNCH. The moveable part that forces the metal into the die in equipment for sheet drawing, blanking, coining, embossing and the like.
PUNCHING. Shearing holes in sheet metal with punch and die.
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