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rabbit ear	A recess in a die corner to allow for wrinkling or folding of the part.
radial draw forming	The forming of sheet metals by the simultaneous application of tangential stretch and radial compression forces. The operation is done gradually by tangential contact with the die member. This type of forming is characterized by very close dimensional control.
ram	See press slide.
ready hemmer	A type of flat surface-straight edge hemming process where pre-hemming and final hemming operations are combined by the use of a rocker (rotary) die set. (See Figure R1)
recoil	As opposed to hem curved outboard and hem deflection recoil is the term used for the local curve at the hem edge. (See Figure R2 and Figure R3)
recoil line	See impact line.
redrawing	The second and successive deep-drawing operations in which cuplike shells are deepened and reduced in cross-sectional dimensions.
reduction	(1) In cupping and deep drawing, a measure of the percentage of decrease from blank diameter to cup diameter, or of the diameter reduction in redrawing. (2) In forging, extrusion, rolling, and drawing, either the ratio of the original to the final cross-sectional area or the percentage of decrease in cross-sectional area.
reduction in area	The difference between the original cross-sectional area and the smallest area at the point of rupture in a tensile test; usually stated as a percentage of the original area.
register	When the workpiece is brought into the required position by the pilots.
relief	Clearance obtained by removing metal either behind or beyond the cutting edge of a punch or die. Also called undercut or back-off.
reset	The realigning or adjusting of dies or tools during a production run; not to be confused with the operation setup that occurs before a production run.
residual stress	Stresses left within a metal as the result of non-uniform plastic deformation or by drastic gradients of temperature from quenching or welding.
response variable	“A variable observed or measured in an experiment, sometimes called a dependent variable. The response variable is the outcome of an experiment and is often a quality characteristic or a measure of performance of the process.” (Moen, R. D., Nolan, T. W., Provost, L. P., 1991, p.406).
restrike	To sharpen radii, form, or detail in previously formed area of a part. Also used to eliminate spring back. Also called spank.
restriking	(1) The striking of a trimmed but slightly misaligned or otherwise faulty forging with one or more blows to improve alignment, improve surface condition, maintain close tolerances, increase hardness, or effect other improvements. (2) A sizing operation in which coining or stretching is used to correct or alter profiles and to counteract distortion. (3) A salvage operation following a primary forging operation in which the parts involved are rehit in the same forging die in which the pieces were last forged.
reverse drawing	Redrawing of a sheet metal part in a direction opposite to that of the original drawing.
reverse flange	A sheet metal flange made by shrinking, as opposed to one formed by stretching.
reverse redrawing	(Inside-out Redrawing) A second or subsequent redrawing operation performed in the opposite direction to the original drawing.
rib	(1) A long V-shaped or radiused indentation used to strengthen large sheet metal panels. (1) A long, usually thin protuberance used to provide flexural strength to a forging (as in a rib-web forging).
rider pin	See guide pin.
ring	See blank holder.
riser	(1) A sub plate on which die steels are mounted. (2) A block of steel or welded construction to which punch steels or punch retainers are mounted. Also called pedestal, punch riser, or stool. (3) A plate, welded construction, or casting mounted to the bottom of the lower die shoe to facilitate scrap removal, regulate feed height, obtain shut height, etc. (4) A cast spacer between the inner ram and the draw punch in a toggle draw die. Also called punch riser.
riser block	A plate inserted between the top of the press bed and the bolster to decrease the height of the die space.
robot hem	(See Figure R4)
rod	A solid round section 9.5 mm (3/8 in.) or greater in diameter, whose length is great in relation to its diameter.
roll bending	The curving of sheets, bars, and sections by means of rolls.
roll flattening	The flattening of sheets that have been rolled in packs by passing them separately through a two-high cold mill with virtually no deformation. Not to be confused with roller leveling.
roll forging	A process of shaping stock between two driven rolls that rotate in opposite directions and have one or more matching sets of grooves in the rolls; used to produce finished parts or preforms for subsequent forging operations.
roll forming	A metal forming process used to produce long components of various cross sections. The sheet metal is formed by passing it through a succession of progressively shaped power-driven contoured rolls.
roll straightener	A mechanism equipped with rolls to straighten sheet or strip stock. Usually used with a feed mechanism for press working.
roll straightening	The straightening of metal stock of various shapes by passing it through a series of staggered rolls (the rolls usually being in horizontal and vertical planes) or by reeling in two-roll straightening machines.
roller leveler breaks	Obvious transverse breaks on sheet metal usually about 3 to 6 MM ('/8 to '/4 in.) apart that are caused by the sheet fluting during roller leveling. These will not be removed by stretching.
roller leveling	Leveling by passing flat sheet metal stock through a machine having a series of small-diameter staggered rolls that are adjusted to produce repeated reverse bending.
rope	The radius on the outside edge of a hemmed part where the diameter of this edge is at least four times stock thickness. The rope is used for materials with insufficient ductility to form an open hem.
rope hem	Preferred for lower strength materials. (See Figure R5)
rose bud	The result of cutting or tearing (piercing) and flanging of a hole in one operation without generating a slug. Referring to extruding or spearing.
rotary file	See carburr.
rotary shear	A sheet metal cutting machine with two rotating-disk cutters mounted on parallel shafts driven in unison.
rough blank	A blank for a forming or drawing operation, usually of irregular outline, with necessary stock allowance for process metal, which is trimmed after forming or drawing to the desired size.
roughing cutter	A milling cutter with serrated flutes or teeth. Also called corn-cobs and multi-tooth cutters.
rubber duck	A flexible skin of a part made out of latex covered fiberglass and used.in the designing of a die.
rubber forming	A sheet metal forming process in which rubber is used as a functional die part.
rubber screw	See Chicago screw.
rubber-pad forming	A sheet metal forming operation for shallow parts in which a confined, pliable rubber pad attached to the press slide (ram) is forced by hydraulic pressure to become a mating die for a punch or group of punches placed on the press bed or baseplate. Developed in the aircraft industry for the limited production of a large number of diversified parts, the process is limited to the forming of relatively shallow parts, normally not exceeding 40 mm (1.5 in.) deep. Also known as the Guefin process. Variations of the Guerin process include the Marforming process, the.fluid-cell process, and fluid forming.
run marker	See run stamps.
run numbers	See run stamps.
run stamps	Stamps used in a die to stamp the date the part was run. Normally this is a Julian date (see Julian date). Also called run marker, run numbers, or date of run.
running clearance	The amount of, clearance designed in a die between two mating steels to allow for stock thickness at bottom of press stroke.