S.O.#

See service order number.

safety pin

A pin which is used to prevent the movement of an object while working on or near that object.  Used on incline cams, iron hands, etc.

sanding bob

A small tightly rolled and glued emery cloth designed to be mounted on a mandrel and used on a hand grinder for polishing.

sausage

See kidney.

saxaphone

Five-eighth inch hand grinder that is big and cumbersome to use.  Used for rough-grinding where there is a large amount of stock to be removed.

scaling

A process used for spotting large contoured areas by using a spotting stick.  See also spotting stick.

scoring

(1) The marring or scratching of any formed part by metal pickup on the punch or die. (2) The reduction in thickness of a material along a line to weaken it intentionally along that line.

scrap

Pieces or parts not normally usable.

scrap cutter

A shear or cutter operated by the press or built into a die for cutting scrap into sizes for convenient removal from the die or disposal.

scrap strip

See skeleton.

screw press

A high-speed press in which the ram is activated by a large screw assembly powered by a drive mechanism.

secant modulus

The slope of the secant drawn from the origin to any specified point on the stress-strain curve.  See also modulus of elasticity.

sections

See details.

segment die

Same as split die.

service order number

Number used to identify special accounts to cover the cost of service work on past model dies only.  Numbers can be found in a book in the supervisor's office.  Also called tool order number and project number.

shadow

See low spot.

shaving

A secondary shearing or cutting operation in which the surface of a previously cut edge is finished or smoothed by removing a minimal amount of stock.

shear

(1) A machine or tool for cutting metal and other material by the closing motion of two sharp, closely adjoining edges; for example, squaring shear and circular shear. (2) An inclination between two cutting edges, such as between two straight knife blades or between the punch cutting edge and the die cutting edge, so that a reduced area will be cut each time.  This lessens the necessary force, but increases the required length of the working stroke.  This method is referred to as angular shear. (3) The act of cutting by shearing dies or blades, as in a squaring shear. (4) The type of force that causes or tends to cause two contiguous parts of the same body to slide relative to each other in a direction parallel to their plane of contact. (5) A tool for cutting metal and other material by the closing of two sharp, closely adjoining edges.  (6) An, inclination between two cutting edges used to avoid cutting all at once. (7) The damage done to the cutting edges of trim steels by misalignment.

shear knives

Steels used for lancing the part in a forming operation to control fracturing of the part while forming.

shear strength

The maximum shear stress a material can sustain.  Shear strength is calculated from the maximum load during a shear or torsion test and is based on the original dimensions of the cross section of the specimen.

shear stress

(1) A stress that exists when parallel planes in metal crystals slide across each other. (2) The stress component tangential to the plane on which the forces act.

shearing

The parting of material that results when one blade forces the material past an opposing blade.

shedder

A pin, rod, ring, or plate operated by mechanical means, air, or a rubber cushion that either ejects blanks, parts, or scrap from a die or releases them from punch, die, or pad surface.

sheet

Any material or piece of uniform thickness and of considerable length and width as compared to its thickness.  With regard to metal, such pieces under 6.5 mm (1/4 in.) thick are called sheets, and those 6.5 MM ('/4 in.) thick and over are called plates.  Occasionally, the limiting thickness for steel to be designated as sheet steel is No. IO Manufacturer's Standard Gage for sheet steel, which is 3.42 mm (0.1345 in.) thick.

sheet forming

The plastic deformation of a piece of sheet metal by tensile loads into a three-dimensional shape, often without significant changes in sheet thickness or surface characteristics.  Compare with bulkforming.

shim

A thin piece of material used between two surfaces to obtain a proper fit, adjustment, or alignment.

shimmy cam

A cam designed to move in one direction land then reverse direction during the down stroke of the press so work is done in both directions.

shims

“Thin metal sheets that are inserted between the die and press to align the binder surface of the die and alter binder pressure” (Automotive Steel Partnership, 1991, p. 14).

shoe

A generic term referring to the upper or lower component of a die set.

shoulder screw

A socket head screw with a larger machined body than the threaded end.  Made to bottom on the body's shoulder.  Used to contain pads or springs and for other tasks.  Sometimes referred to as shoulder or stripper bolts.

shut height

“The distance from the top of the bed to the bottom of the slide with the stroke down and adjusted up.  In general, the shut height of a press is the maximum die height that can be accommodated for normal operation, taking the bolster into consideration.” (Automotive Steel Partnership, 1991, p. 14).

shute

See chute.

single-action die

A form die that has no blankholder action since it is used with a single-action press without the use of a draw cushion.

single-action press

Any press with a single slide.  Usually considered to be without any other motion or pressure device.

sizing

(1) Secondary forming or squeezing operations needed to square up, set down, flatten, or otherwise correct surfaces to produce specified dimensions and tolerances.  See restriking. (2) Some burnishing, broaching, drawing, and shaving operations are also called sizing. (3) A finishing operation for correcting ovality in tubing. (4) Final pressing of a sintered powder metallurgy part.

skeleton

The strip of stock from a progressive die starting at he point of entry through the last station.  Also called stock strip, scrap strip, or carrier strip.  Also see web.

skid lines

Line seen on the finished part when the stock slips on a draw punch.  This is caused by the die not being timed correctly or when the forming of a shape is at such an off angle.

skid marks

See draw marks.

skin

(1) A thin reproduction of the outside surface of a part detail, or model.  Normally made of fiberglass and/or a plastic material.  Used for spotting, machining, etc. (2) Outer panel of car such as outer hood.

sled irunner

An adjustable tripper for activating an air.operated valve which controls automation.  Also called, striker.

slide

The main reciprocating member of a press, guided in the press frame, to which the punch or upper die is fastened; sometimes called the ram.  The inner slide of a double-action press is called the plunger or punch-holder slide; the outer slide is called the blankholder slide.  The third slide of a triple-action press is called the lower slide, and the slide of a hydraulic press is often called the platen.

slide adjustment

The distance that a press slide position can be altered to change the shut height of the die space.  The adjustment can be made by hand or by power mechanism.

slide counterbalance

A device used on the slide of large and small presses to reduce vibration and to assist the brake and clutch in functioning properly.  Counterbalances are actuated by springs or air pressure.  They relieve much of the load of the slide and punch from the press connection and shaft, thereby reducing the friction on the brake.

slide counterbalance pressure (counterbalance pressure)

“A device used on the slide of large and small presses to reduce vibration and to assist the brake and clutch in functioning properly.  Counterbalances are actuated by springs or air pressure.  They relieve much of the load the slide and punch from the press connection and shaft, thereby reducing the friction on the brake.” (Automotive Steel Partnership, 1991, p. 15).

slide hammer

(1) A weight that slides along a rod with a head on one end and threads on the other end.  Normally used to pull dowels and details.  Commonly called a dowel puller.

slitting

Cutting or shearing along single lines to cut strips from a sheet or to cut along lines of a given length or contour in a sheet or workpiece.

slug

(1) The metal removed when punching a hole in a forging; also termed punchout. (2) The forging stock for one workpiececut to length.  See also blank.

slug trails

• (1) Passage ways for slugs to fall out of trim and pierce dies.
• (2) Slug marks in draw and form dies.

spalling

The breaking off of flake - like metal particles from a metal surface.

spank

See restrike.

spares

See back-ups.

spear punching

The process of cutting or tearing a hole in metal which does not generate a slug.  Instead, the metal is pushed back to form a jagged flange on the back side of the hole.  Also called spearing.  One form of extruding.

spearing

See spear punching or extruding.

spider

A plate that bridges two or more transfer pins and distributes force equally.  Commonly used for lifter, light weight pads, and positive knockouts.

spinning

The forming of a seamless hollow metal part by forcing a rotating blank to conform to a shaped mandrel that rotates concentrically with the blank.  In the typical application, a flat-rolled metal blank is forced against the mandrel by a blunt, rounded tool; however, other stock (notably, welded or seamless tubing) can be formed.  A roller is sometimes used as the working end of the tool.

spleen

See draw bead.

split die

A die made of parts that can be separated for ready removal of the workpiece.  Also known as segment die.

splits

“Failure and localized separation of a sheet metal, also known as tears or fractures.” (American Deep Drawing Research Group, 1981).

spool

A cylindrical headed keeper fastened by one or more socket head screws used to retain and control pad travel.

spot face

The process of providing a smooth surface for a fastener.  Also called sump.  Also refers to the smooth area around a hole for a fastener.

spotting

The fitting of one part of a die to another by applying an oil or water color to the surface of the finished part and bringing it against the surface of the intended mating part, the high spots being marked by the transferred color.

spotting aid

See skin or cast.

spotting rack

See skin or cast.

spotting scale

A thin hardened steel rule type material used to locate high points or areas when spotting large form areas such as hood punches.

spotting stick

A thin strip of wood used to locate high points or areas when spotting large form areas such as hood punches.  The stick is usually made of mahogany. Also called mahogany stick.  See also scaling.

spring can

A sheet metal cylinder open at one end and closed at the other.  Used to retain the various segments of a spring in the event that it breaks.

spring plate

A separately mounted plate used to retain and provide access to die springs.

springback

(1) The elastic recovery of metal after stressing. (2) The extent to which metal tends to return to its original shape or contour after undergoing a forming operation.  This is compensated for by overbending or by a secondary operation of restriking. (3)The extent to which metal tends to return to its original shape or position after undergoing a forming operation. See buckling. (See Figure S1)

spring-back allowance

The allowance designed into a die for bending metal a greater amount than specified for the finished piece, to compensate for spring-back.

squeeze block

A piece of steel with a spring-loaded pin held under tension by a screw.  Used to check distance between two parallel surfaces or press ram adjustment.

stack up

Thickness of hem area after final hem. (See Figure S2)

staking

The process of permanently fastening two parts together by recessing one part within the other and then causing plastic flow of the material at the joint.

stamp

(1) The general term to denote all press workings. (2) To impress lettering or designs by pressure into the surface of a material.

stamping flange angle

Angle measured from the mating flange area to the upturned flange formed by the flanging operation. (See Figure S3)

standoff blocks

(1) See stop blocks. (2) See leveling blocks.

starting ring

See pre-hem steel.

starting steel

See pre-hem steel.

steel rule die

A die employing a thin strip of steel formed to the outline of a part and a flat metal plate or block of wood for the punch.  Used to cut non-metallic material, soft metals, and low run prototype sheet metal parts.  Also called cookie cutter die.

steels

See details.

stitch and run die

Staking same size blanks together with each stroke of the press forming a continuous strip.  Then feeding this staked strip thru the die as in a coil.

stock

A general term used to refer to a supply of metal in any form or shape and also to an individual piece of metal that is formed, forged, or machined to make parts.

stock guide

A device used to direct a strip or sheet material thru the die.

stock strip

See skeleton.

stone

A coarse grit hone that is used dry.

stool

(1) Lower section of a die on which the part nests.  Also called lower adapter, boss, die post, horn, locator, master, or master plug. (2) A base for a punch retainer to enable the punch to reach thru the, pad or stripper.  Also called a pedestal, punch riser, and riser.

stop

A device for positioning stock or parts in a die.

stop blocks

“Blocks normally located near each rider pin to prevent the die from closing too far.  Used to determine the proper ram adjustment.  Also called stand off blocks and bottoming blocks.” (Automotive Steel Partnership, 1991, p. 16).

stop pin

A device for positioning stock or parts in a die.

stop, automatic

(1) A device for positioning stock in a die. (2) A mechanism that initiates the stopping action of a press after its complete cycle.

(3) A device which initiates the stopping action of a press at the start of operating troubles for protecting either the die or the operator, such as misfeeding, buckling of strip stock, or non-discharge of blanks.

storage blocks

Urethane blocks generally used in trim and pierce dies to prevent chipping of steels during storage and handling.  Also aids in noise reduction, leveling the press ram, and reducing die shock.

straight cam

A cam that travels 90⁰ to press stroke.  Also called horizontal cam.

straight perimeter contour

Curvature of the peripheral edge that has no radius. (See Figure S4)

straightener rolls

See roll straightener.

straight-side press

An upright press open at front and back with the columns (uprights) at the ends of the bed.

strain

“A normalized measure of deformation.  Strains may be either positive (elongation) or negative (compression), and may be either elastic (recoverable) or plastic (permanent).” (GM Die Dictionary, 1995, p. 58).

strain aging

The changes in ductility, hardness, yield point, and tensile strength that occur when a metal or alloy that has been cold worked is stored for some time.  In steel, strain aging is characterized by a loss of ductility and a corresponding increase in hardness, yield point, and tensile strength.

strain hardening

An increase in hardness and strength caused by plastic deformation at temperatures below the recrystallization range.  Also known as work hardening.

strain-hardening coefficient

See strain hardening exponent.

strain-hardening exponent

The value n in the relationship  = KEⁿ, where  is the true stress; E is the true strain; and K, which is called the strength coefficient, is equal to the true stress at a true strain of I.O. The strain-hardening exponent, also called n-value, is equal to the slope of the true stress/true strain curve up to maximum load, when plotted on log-log coordinates.  The n-value relates to the ability of a sheet material to be stretched in metalworking operations. The higher the n-value, the better the formability (stretchability).

strain-rate sensitivity (m value)

The increase in stress () needed to cause a certain increase in plastic strain rate (i) at a given level of plastic strain (E) and a given temperature (T). Strain-rate sensitivity = m = A log a@ (A log i).T stress.  The intensity of the internally distributed forces or components of forces that resist a change in the volume or shape of a material that is or has been subjected to external forces.  Stress is expressed in force per unit area.  Stress can be normal (tension or compression) or shear.

stress

The internal force or forces set up within a body by outside applied forces or loads.

stress cracking

The fracturing of parts which have retained residual stresses from cold forming, heat treating, or rapid cooling.

stress raisers

Design features (such as sharp corners) or mechanical defects (such as notches) that act to intensify the stress at these locations.

stress relief

(Relieving) A heat treat process which is used to reduce residual stresses in a steel.

stress-strain curve

See stress-strain diagram.

stress-strain diagram

A graph in which corresponding values of stress and strain from a tension, compression, or torsion test are plotted against each other.  Values of stress are usually plotted vertically (ordinates or y-axis) and values of strain horizontally (abscissas or x-axis).  Also known as deformation curve and stress-strain curve.

stretch drawing

The process of holding a blank with an upper and lower ring, the lower ring being mounted on a nitrogen actuated pressure pad.  Both upper and lower rings are lowered to a dwell position stretching the material over the lower die.  The upper die then closes to complete the forming operation of this die.

stretch former

(1) A machine used to perform stretch forming operations. (2) A device adaptable to a conventional press for accomplishing stretch forming.

stretch forming

The shaping of a sheet or part, usually of uniform cross section, by first applying suitable tension or stretch and then wrapping it around a die of the desired shape.

stretcher leveling

The leveling of a piece of sheet metal (that is, removing warp and distortion) by gripping it at both ends and subjecting it to a stress higher than its yield strength.

stretcher straightening

A process for straightening rod, tubing, and shapes by the application of tension at the ends of the stock.  The products are elongated a definite amount to remove warpage.

stretcher strains

Elongated markings that appear on the surface of some sheet materials when deformed just past the yield point.  These markings lie approximately parallel to the direction of maximum shear stress and are the result of localized yielding.  See also Luders lines.

stretching

The extension of the surface of a sheet in all directions.  In stretching, the flange of the flat blank is securely clamped.  Deformation is restricted to the area initially within the die.  The stretching limit is the onset of metal failure. The “n” in the equation  = Kⁿ which equates the true stress to the true strain of a material under plastic deformation.  The n-value is measured from a tensile test by finding the slope of the true-stress to true-strain in the plastic region.  It is also referred to as the n-value.  Figure S5 depicts how to calculate the n-value.

striker

See sled runner.

striking surface

Those areas on the faces of a set of dies that are designed to meet when the upper die and lower die are brought together.  The striking surface helps protect impressions from impact shock and aids in maintaining longer die life.

strip

A flat-rolled metal product of some maximum thickness and width arbitrarily dependent on the type of metal; narrower than sheet.

stripper

A plate designed to remove, or strip, sheet metal stock from the punching members during the withdrawal cycle.  Strippers are also used to guide small precision punches in close-tolerance dies, to guide scrap away from dies, and to assist in the cutting action.  Strippers are made in two types: fixed and movable.

stripper bolts

See shoulder screw.

stripper insert

See window.

stripper plates

A plate (solid or moveable) used to strip the workpiece or part from the punch.  It may also guide the stock.

stripper punch

A punch that serves as the top or bottom of the die cavity and later moves farther into the die to eject the part or compact.  See also ejector rod and knockout.

stripping

The operation of removing the workpiece or part from the punch.

stroke (up or down)

The vertical movement of a ram during half of the cycle, from the full open to the full closed position or vice versa.

stroke of a press

The reciprocating motion of a press slide, specified as the number of inches between the terminal points of the motion.

sump

• (1) A formed recess area of a part usually for clearance. 
• (2)  See spot face.

superior hone

A tool which employs bonded abrasive stones in a special holder to remove stock and improve surface finish of holes.

superplasticity

The ability of certain metals to develop extremely high tensile elongations at elevated temperatures and under controlled rates of deformation.

support plate

A plate that supports a draw ring or draw plate.  It also serves as a spacer.

surface distortion

Surface distortions are wrinkles formed on the grade-A surfaces of panels due to improper hemming operation. (See Figure S6)

surge tank

A tank designed to accept a volume of air, gas on the compression stroke of a cylinder and to provide an extra volume of air, gas, or oil on the power stroke of the cylinder.  Also prevents excess pressure buildup in a cylinder and/or lines.

swift cup test

A simulative test in which circular blanks of various diameter are clamped in a die ring and deep drawn into a cup by a flat-bottomed cylindrical punch.  The ratio of the largest blank diameter that can be drawn successfully to the cup diameter is known as the limiting drawing ratio (LDR) or deformation limit.

swivel ring

A load-centering eye bolt which allows the eye to pivot 180⁰ and the base to swivel 360⁰ to allow pulling at any angle without fear of bending or breaking the bolt.  Also called hoist ring.