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Z94.12.4 Metal Forming

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BACK-GAGE. A surface on two or more supports located behind the shear that can be positioned accurately either manually or automatically to control part size.

BED, PRESS. The stationary part of the press serving as a table to which is affixed the bolster, or sometimes, the lower die directly.

BEAD. A narrow ridge is a sheet metal workpiece or part, commonly formed for reinforcement.

BENDING. The straining of material, usually flat sheet or strip metal, by moving it around a straight axis which lies in the neutral plane. Metal flow takes place within the plastic range of the metal, so that the bent part retains a permanent set after removal of the applied stress. The cross section of the bend inward from the neutral plane is in compression; the rest of the bend is in tension.

BENDING BRAKE OR PRESS BRAKE. A form of open-frame, single-action press comparatively wide between the housings, with bed designed for holding long, narrow forming edges or dies. It is used for bending and forming strips and plates, as well as sheets (made into boxes, panels, roof decks, etc.).

BENDING DIES. Dies used in presses for bending sheet metal or wire parts into various shapes. The work is done by the punch pushing the stock into cavities or depressions of similar shape in the die or by auxiliary attachments operated by the descending punch.

BENDING ROLLS. Staggered rolls (usually three) adjusted to put the desired curvature in a plate or used for coiling and uncoiling strip or wire.

BENDING STRESS. A stress involving both tensile and compressive forces which are not uniformly distributed. Its maximum value depends on the amount of flexure that a given application can accommodate. Resistance to bending may be called "stiffness.'' It is a function of the modulus of elasticity and, for any metal, is not affected by alloying or heat treatment.

BEND RADIUS. The radius corresponding to the curvature of a bent specimen or bent area of a formed part, and measured on the inside of a bend.

BEND TESTS. Various tests used to determine the ductility of a sheet or plate that is subjected to bending. These tests may include determination of the minimum radius or diameter required to make a satisfactory bend and the number of repeated bends that the material can withstand without failure when it is bent through a given angle and over a definite radius.

BLADE. A replaceable tool having one or more cutting edges.

BLANK. A pressed presintered or fully sintered compact, usually in the unfinished condition and requiring cutting, machining, or some other operation to produce the final shape.

BLANKHOLDER. The tool that prevents the rim of a sheet metal blank from wrinkling while it is being deep drawn.

BLANKHOLDER SLIDE. The outer slide of a multiple-action press. It is usually operated by toggles or cams.

BLANKING. Shearing out a piece of sheet metal in preparation for deep drawing.

BLANKING DIE. A die used for shearing or cutting blanks usually from sheets or strips. The single blanking die used for producing one blank at each stroke of the press is the simplest of all dies, consisting essentially of punch, die block, and stripper.

BLUE BRITTLENESS. Reduced ductility occurring as a result of strain aging, when certain ferrous alloys are worked between 300° and 700°F. This phenomenon may be observed at the working temperature or subsequently at lower temperatures.

BOARD HAMMER. A type of drop hammer in which boards attached to the ram are lifted between rollers.

BOLSTER PLATE. A plate attached to the top of the press bed for locating and supporting the die assembly. It usually has holes or T-slots for attaching the lower die or die shoe. Moving bolster plates are self powered for transferring dies in and out of the press for die setting. Also called rolling bolsters, they may be integral with or mounted to a carriage. They are not to be confused with sliding bolsters, the purpose of which is moving the lower die in and out of the press for workpiece feeding.

BOTTOMING BENDING. Press brake bending process in which the upper die (punch) enters the lower die and coins or sets the material to eliminate springback.

BOW. The tendency of material being sheared to curl downward during shearing, particularly when shearing long narrow strips.

BRAKE. A piece of equipment used for bending sheet; also called a "bar folder." If operated manually, it is called a "hand brake," if power driven it is called a "press brake."

BRALE. A diamond penetrator, conical in shape, used with a Rockwell hardness test for hard metals.

BUCKLING. A bulge, bend, kink, or other wavy condition of the workpiece caused by compressive stress.

BUFF. A polishing wheel usually consisting of a large number of treated or untreated muslin disks sewed together.

BULGING. The process of increasing the diameter of a cylindrical shell (usually to a spherical shape) or of expanding the outer walls of any shell or box shape whose walls were previously straight.

BULL BLOCK. A power-driven reel for drawing heavy-gage wire through a die.

BULLDOZER. Slow-acting horizontal mechanical press with large bed used for bending, straightening, etc. The work, which is done between dies, may be performed either hot or cold. The machine is closely allied to a forging machine.

BURNISHING. (1) Plastic smearing such as may occur on metallic surfaces during buffing. (2) The result of the moveable blade rubbing against the edge of the sheared material due to a blade clearance that is adjusted too tight.

BURNT. A term applied to a metal permanently damaged by having been heated to a temperature close to the melting point.

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