back-draft:

The area of a part that cannot be formed when in . die position with direct vertical travel of the press ram.

background variable

“A variable that potentially can affect a response variable in an experiment but is not of interest as a factor; sometimes called a noise variable or blocking variable” (Moen, R. D., Nolan, T. W., Provost, L. P., 1991, p.402).

back-off

See relief.

back-ups

(1) Perishable details made ahead and stored in a crib or back-up area.  Sometimes called spares.  Also see details. (2) Keys or spacer plates mounted behind a die detail to reinforce that detail.

balancing pins

See equalizer pins.

ball seat

A tear drop shaped area machined in the shank of a punch by a ball nose cutter.  This allows the punch to be accurately located and locked in a retainer by a ball.

barber shop

An area usually designated just for barbering of dies.

barbering

Rough grinding, by hand, of excess stock in a die.

bead

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

bead

(1) Stationary platen of a press to which the lower die assembly is attached. (2) Stationary part of the shear frame that supports the material being sheared and the fixed blade.

beaded flange

A flange reinforced by a low ridge, used mostly around a hole.

bellmouth

The angular condition on the working surface of a trim or form steel caused by excessive wear.

bend angle

The angle through which a bending operation is performed, that is, the supplementary angle to that formed by the two bend tangent lines or planes.

bend radius

The inside radius of a bent section.

bendability

It is defined as the minimum bending radius (shown as R_i, inner radius) attainable by a given material. (See Figure B1)

bending

The straining of material, usually flat sheet or strip metal, by moving it around a straight axis lying 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.  See also bending stress.

bending brake or press brake

A form of open-frame single-action press that is comparatively wide between the housings, with a bed designed for holding long, narrow forming edges or dies.  Used for bending and forming strip, plate, and sheet (into boxes, panels, roof decks, and so on).

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

Various types of machinery equipped with two or more rolls to form curved sheet and sections.

bending stress

A stress involving 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 can be termed stiffness.

BHF

See blank holder force.

BHP

See blank holder pressure.

binder

“The upper and lower holding surfaces which control metal flow around a shape to be formed in a draw operation” (Automotive Steel Partnership, 1991, p.2).  Also see blank holder and draw ring.

binder force

See blank holder force.

binder ring

See blank holder.

bird bath

See low spot.

bladesteel

A long narrow trim steel quite often mounted from the side.  Also see details.

blank

(1) In forming, a piece of sheet material, produced in cutting dies, that is usually subjected to further press operations. (2) A piece of stock from which a forging is made; often called a slug or multiple.  (3) “A pre-cut metal shape for a subsequent press operation” (Automotive Steel Partnership, 1991, p.2).

blank development

(1) The technique of determining the size and shape of a blank.  (2) The resultant flat pattern.

blank holder

The part of a draw die which holds the work piece against the draw ring to control metal flow.  A blank holder is also called binder, binder ring, or ring.  That part of a forming die which holds the blank by pressure against a mating surface of the die to control metal flow and prevent wrinkling.  The blank holder is sometimes referred to as “hold down” or binder area.  Pressure applied by mechanical means, springs, air, or fluid cushions (Automotive Steel Partnership, 1991, p.2).

blank holder force

Blank holder force is applied to the perimeter of a sheet during a deep drawing operation to suppress wrinkling and control metal flow. See Figure B2 for a schematic of blank holder force. See Figure B3 for blank holder force trajectories.

blank holder pressure

Blank holder pressure is the pressure pattern on the blank that results from applying a blank holder force. “The pressure exerted by the blank holder against the blank.  This pressure is normally adjustable to control metal flow during the drawing.” (Automotive Steel Partnership, 1991, p.2).

blanking

The operation of punching, cutting, or shearing a piece out of stock to a predetermined shape.

blocking variable

“A variable that potentially can affect a response variable in an experiment but is not of interest as a factor grouped by experimental units treated in a similar way in an experimental design” (Moen, R. D., Nolan, T. W., Provost, L. P., 1991, p.402).

bologna

See kidney.

bolster plate

A plate to which dies can be fastened- the assembly is secured to the top surface of a press bed.  In press forging, such a plate may also be attached to the ram.

boss

(1) See adapter. (2) A raised portion of a casting, die, or part such as bosses for tie slots on die shoes.

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.

bottoming blocks

(1) Adjustable blocks mounted under a pad to determine the proper height of the pad when the die is closed. (2) Also see stop blocks.

bottoming stamp

“A stamp or weld mark used in a form die to signify that the die is on the bottom.  Usually positioned in a scrap area of the part” (Automotive Steel Partnership, 1991, p.2).

bottoming the die

See homing the die.

box cam

A precision made box containing cam slide and driver.

box heels

See heel block.

breakage

The space, per side, between the punch and die on a trim or pierce die.  Also called clearance or die clearance.

breathing

The non-desired action of a die member moving away from the force applied.

bubble die

A pre-draw die to gain material in the areas of a deep draw to help prevent the fracture of the metal in these areas.

buckling

(1) An uncontrolled deformation pattern perpendicular to the surface of a sheet caused by compressive stresses.  Buckling in the flange of the part is referred to as wrinkling, and buckling in the wall of the part is referred to as puckering.  See Figure B4 for an example of buckling in the drawing of cups.  (2) A bulge, bend, kink, or other wavy condition of the workpiece caused by compressive stresses.

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.

bumper-actuated die

See free-shoe die.

burr

A thin ridge or roughness left on forgings or sheet metal blanks by cutting operations such as slitting, shearing, trimming, blanking, or sawing.

burring

A common term for debarring or smoothing the rough cut edges of metal.

buster

A pair of shaped dies used to combine preliminary forging operations, such as edging and blocking, or to loosen scale.

button

A small cylindrical die steel with an opening larger than the punch point size, generally by a percentage of the thickness of the material being pierced.  Also called die button or pierce button.

bypass

A generic term referring to the amount that one steel passes over or thru another steel.