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Metal forming and welding glossary - R

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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

Driven (movable) part of a metalforming machine.

Rapid prototyping

This includes a number of rapidly evolving techniques for making prototypes and models quickly thus allowing designers to check their designs and make any necessary changes before investing in expensive tooling. A CAD model of the part is required and the model is usually built layer by layer.

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.

Rear cut off

A device on a slide forming machine driven by a cam that is mounted on the rear shaft allowing the removal of a slug from the strip, thus providing the ability to produce a blank with special end shapes.

Recoil

As opposed to hem curved outboard and hem deflection recoil is the term used for the local curve at the hem edge.

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

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. 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 that is usually stated as a percentage of the original area.

Register

When the workpiece is brought into the required position by the pilots.

Reinforced weld

The weld metal built up above the surface of the two abutting sheets or plates in excess of that required for the size of the weld specified.

Relief

Clearance obtained by removing metal either behind or beyond the cutting edge of a punch or die. Also called undercut or back-off.

Repositioning

Operation in turret press fabrication denoting the release of the workholders, movement of the X axis to a new position on the workpiece, and the regripping of the workpiece so that a sheet larger than the X axis table travel can be fabricated, all under computer numeric control (CNC).

Reproducibility

Extent to which parts from multiple lots are identical.

Rerolling

Final cold rolling operation, usually done to achieve specific thickness control and improved finish.

Reservoirs

A tank used to store fluid for a hydraulic system - this maintains the fluid an even temperature by allowing circulation and cooling from the tank sides.

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

Macroscopic stresses that are set up within a metal as the result of non-uniform plastic deformation. This deformation may be caused by cold working or by drastic gradients of temperature from quenching or welding.

Resistance butt welding (RPW)

A group of resistance welding processes in which the weld occurs simultaneously over the entire contact area of the parts being joined.

Resistance Projection Weld (RPW)

See projection weld.

Resistance Spot Welding (RSW)

Melting and joining action of two adjoining metal surfaces created by the thermal reaction of the metal to the flow of an electrical current forming a weld nugget.

Resistance welding

Refers to a group of welding processes such as spot and seam welding that produce coalescence of faying surfaces where heat to form the weld is generated by the resistance of the welding current through the workpieces. Some factors influencing heat or welding temperatures are the proportions of the workpieces, the electrode materials, electrode geometry, electrode pressing force, weld current and weld time, etc. Small pools of molten metal are formed at the point of most electrical resistance (the connecting surfaces) as a high current (100–100 000 A) is passed through the metal. In general, resistance welding methods are efficient and cause little pollution, but their applications are limited to relatively thin materials and the equipment cost can be high.

Restrike

To sharpen radii, form, or detail in previously formed area of a part. Also used to eliminate spring back. Also called spank.

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.

Revision

A subsequent part drawing usually denoting new corrected or improved version.

Revision description

A written notice describing the nature of changes to a drawing.

Rib

A long V-shaped or radiused indentation used to strengthen large sheet metal panels. A long, usually thin protuberance used to provide flexural strength to a forging (as in a rib-web forging).

Ribbing

A coating defect consisting of a flow mark defect with an appearance similar to corduroy fabric. Ribbing usually occurs when the flow marks (ribs) from application on the coater do not flow out and level the surface of the coating.

Ribbon wound

A term applied to a common method of winding strip steel layer upon layer around an arbor or mandrel.

Rider pin

The pin or post, usually fixed in the lower shoe of a die and accurately fitted to bushings in the upper shoe to insure precise alignment of the two members of a die set. See guide pin.

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. See blank holder.

Riser

A sub plate on which die steels are mounted. A block of steel or welded construction to which punch steels or punch retainers are mounted. Also called pedestal, punch riser, or stool. 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. A cast spacer between the inner ram and the draw punch in a toggle draw die.

Riser block

A plate inserted between the top of the press bed and the bolster.

Rivet nut

Internally threaded fastener designed to be used as a rivet from one side of a workpiece or assembly and to provide threads for a screw or bolt to be used in assembly of a mating part.

Rockwell hardness

An indentation hardness test based on the depth of penetration.

Rockwell (Hardness Tester)

A device used to determine the hardness of the steel strip.

Rod

A solid round section 9.5 mm (3/8') 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 form

A metal shape that has been processed using roll forming.

Roll formed shape, hollow

A roll formed shape which is closed by mechanically fastening or a welding the two strip edges together.

Roll formed shape, open

A roll formed shape with a linear or curved contour in which the two ends of the shape are not brought together.

Roll forming

A continuous bending operation in the metal forming process, which sheet or strip metal is plastically deformed along a linear axis by being passed through a series of roller dies and progressively shaped to the desired contour.

Roll over

The area of material next to the penetrating edge of a piercing punch, or die edge of the blanking station, where the material yields, i.e. flows in the direction of the applied force, creating a rounded edge. Also known as pull down.

Roll stations

Tandem sets of rolls used in roll forming to shape the metal stock in a series of progressive stages to form the desired cross-sectional configuration.

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

A deforming instrument having a work-engaging, work-deforming, peripheral surface which is generated by a line revolving about an axis. The roller will cyclically move into and out of contact with a work surface during deformation of the work, relative movement occurring, during deformation.

Roller level

A staggered system of rolls used to flatten the steel without any appreciable reduction in gauge.

Roller leveler breaks

Obvious transverse breaks on sheet metal usually about 3 to 6 MM (1/8" to 1/4") apart that are caused by the sheet fluting during roller leveling. These will not be removed by stretching.

Rolling

A term applied to the operation of shaping and reducing metal in thickness by passing it between rolls which compress, shape and lengthen it following the roll pattern.

Rolling direction (in rolled metal)

The direction, in the plane of the sheet, perpendicular to the axes of the rolls during rolling.

Rolling mills

Equipment used for rolling down metal to a smaller size or to a given shape employing sets of rolls tie contours of which determine or fashion the product into numerous intermediate and final shapes, e.g., blooms, slabs, rails, bars, rods, sections, plates, sheets and strip.

Roll-over

See pull down.

Root

See Root Of Joint and Root Of Weld, shown below.

Root crack

A crack in the weld or base metal which occurs at the root of a weld.

Root edge

The edge of a part to be welded which is adjacent to the root.

Root face

The portion of the prepared edge of a member to be joined by a groove weld which is not beveled or grooved.

Root of joint

That portion of a joint to be welded where the members approach closest to each other. In cross section, the root of a joint may be a point, a line, or an area.

Root of weld

The points at which the bottom of the weld intersects the base metal surfaces.

Root opening

The separation between the members to be joined at the root of the joint.

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.

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.

Rotary slide machine

A vertical forming machine with the ability to place several forming slides radially around the center tool and produce intricately formed stampings and wire forms.

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.

Roughness (normal and extreme)

Units: mm (SI), mils (Imperial) The 'normal' range of RMS (root mean square) surface roughness which lies within the capacity of the process. As with mass, an 'extreme' range is also stored. Surface roughness is determined by the nature of the process: the smoothness of mold surfaces in casting and molding or the depth of cut in machining. It can usually be refined by machining, grinding and polishing.

Roundness

Extent to which a feature is circular.

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

A socket head cap screw with the head and the upper portion of the body turned down, leaving a minimum number of threads on the end of the body. Used where the screw hole in the detail does not align with the threaded hole in the mounting surface. Also called Chicago screws, Eberly screws, or Kelly screws.

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 out flange

Feature on a formed part which is designated by the designer to absorb the tolerance accumulations created by multiple forming operations.

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.

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