Glossary

ALL

Shoe

A holder used as a support for the stationary portions of forging and trimming dies.

Shot blasting

A process of cleaning forgings by propelling metal shot at high velocity by air pressure or centrifugal force at the surface of the forgings. See also Blast cleaning.

Shrink scale

A measuring scale or rule, used in die layout, on which graduations are expanded to compensate for thermal contraction (shrinkage) of the forging during cooling.

Shrinkage

The contraction of metal during cooling after hot forging. Die impressions are made oversize according to precise shrinkage scales to allow the forgings to shrink to design dimensions and tolerances.

Shut height

For a press, the distance from the top of the bed to the bottom of the ram with the stroke down and adjustment up. In general, it is the maximum die height that can be accommodated for normal operation, taking the bolster plate into consideration.

Shuts (cold)

Faults produced in a forging by incorrect tool design or incorrect flow of steel that results in the formation of a crack in the forging surface.

Side thrust

Lateral force exerted between the dies by reaction of the forged piece on the die impressions.

Side thrust

Lateral force exerted between the dies by reaction of the forged piece on the die impressions.

Sinking

The operation of machining the impression of a desired forging into die blocks.

Sizing

Secondary forming or squeezing operations needed to square up, set down, flatten, or otherwise correct surfaces to produce specified dimensions and tolerances. Often accomplished with a coining press. See Coining.

Sliver

A slender fragment or splinter that is a part of the material, but that is incompletely attached. A torn fiber of metal forced into the surface of a forging.

Slot furnace

A common batch-type forge furnace where stock is charged and removed through a slot or opening.

Slug

(1) Forging stock for one workpiece cut to length. See also Blank. (2) Metal removed when punching a hole in a forging (also termed “punchout”).

Smith

The blacksmith, forger, or pressman.

Smith hammer

Any power hammer where impression dies are not used for the reproduction of commercially exact forgings.

Snag grinding (snagging)

The process of removing portions of forgings not desired in the finished product, by grinding.

Sow block

A block of heat-treated steel placed between a hammer anvil and a forging die to prevent undue wear to the anvil. Sow blocks are occasionally used to hold insert dies. Also called Anvil cap.

Split die

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

Splitter impression

(1) A die cavity used to divide laterally or split the material being worked so that it better covers the impression and reduces forging load; (2) A die cavity used to cut the material apart in the desired section by means of a shearing action.

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.

Stainless steels

Steels that are corrosion and heat resistant and contain a minimum of 10% to 12% chromium. Other alloying elements are often present.

Stamp (marking)

An operation performed to identify the particular forgings as specified or requested by the customer.

Station

A regular stopping place in the die during the forging sequence.

Steam hammer

A type of drop hammer where the ram is raised for each stroke by a double-action steam cylinder and the energy delivered to the workpiece is supplied by the velocity and weight of the ram and attached upper die driven downward by steam pressure. Energy delivered during each stroke may be varied.

Stock

The material to be forged regardless of form. Also, an individual piece of metal used to produce a single forging.

Stock marks

In cutting forging stock to specified length for a die-forged part, the ends of the bar always contain surface imperfections caused by the cutting tool; these are often retained on the surface of the finished part. If pronounced, such marks are removed by light grinding. On parts where repeated indications of stock marks are encountered, efforts are usually made to eliminate them by conditioning the stock ends prior to forging by polishing the cut ends and beveling the edge of the cut.

Straighten

Finishing operation for correcting misalignment in a forging or between different sections of a forging. Straightening may be done by hand, with simple tools, or in a die in forging equipment.

Straighten, coin

A combination coining and straightening operation performed in special cavity dies designed to impart a specific amount of working in specified areas of the forging to relieve stresses set up during heat treatment.

Straighten, die

A straightening operation performed in either a hammer or a press using flat or cavity dies to remove undesired deformation and bring the forging within straightness tolerance.

Straighten, hand

A straightening operation performed on a surface plate to bring a forging within straightness tolerance. Frequently, a bottom die from a set of finish dies is used instead of a surface plate; hand tools used include mallets, sledges, blocks, jacks, and oil gear presses, in addition to regular inspection tools.

Strain hardening

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

Stripper

A lug or ring on the forging or an impression in the dies of a mechanical upsetter to ensure firm clamping of the workpiece in the gripper dies.

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 and Knockout.

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.

Structural integrity

Inherent microstructural soundness of forgings as a result of achieving 100% density, uniform metallurgical structure and grain size, as well as the absence of porosity, segregation, large inclusions, and other non-forged part defects.

Sub-sow block (die holder)

A block used as an adapter in order to permit the use of forging dies that otherwise would not have sufficient height to be used in the particular unit or to permit the use of dies in a unit where the shank sizes are different.

Suck-in

A defect caused by the “sucking in” of one face of a forging to fill a projection on the opposite side.

Superalloys

A term broadly applied to iron-base, nickel-base, and cobalt-base alloys, often quite complex, that exhibit high elevated-temperature mechanical properties and oxidation resistance.

Superplasticity

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

Swaging

(1) Reducing the diameter of or rounding out a section of a forging by a series of blows, tapering the forging lengthwise until the entire section attains the smaller dimension of the taper. (2) Tapering forging stock by forging, hammering, or squeezing.

Table mill

In ring rolling, a type of ring forging equipment employing multiple mandrels with a common main roll. Usually used in high volume production of small-diameter rolled rings.

Target machining

Incorporating a “target” (benchmark or gage point) on a forging to facilitate machining; coined locating surfaces and drilled centers are commonly used.

Template (Templet)

A gage or pattern made in a die department, usually from sheet steel; used to check dimensions on forgings and as an aid in sinking die impressions in order to correct dimensions.

Thermal cracks

Ruptures in metal set up by stresses due to thermal differentials.

Thermal stress

Stresses in metal resulting from non-uniform distribution of heat.

Thermomechanical working

A general term covering a variety of processes combining controlled thermal and deformation treatments to obtain synergistic effects, such as improvement in strength without loss of toughness.

Tolerance

The permissible deviation from a specification for any design characteristic.

Tong hold

The portion of the forging billet, usually on one end, that is gripped by the operator’s tongs. It is removed from the part at the end of the forging operation. Common to drop hammer and press-type forging.

Tongs

Metal holder used to handle hot or cold forgings.

Tool steel

A superior grade of steel made primarily for use in tools and dies.

Tooling marks

Indications imparted to the surface of the forged part from dies containing surface imperfections or dies on which some repair work has been done. These marks are usually slight rises or depressions in the metal.

Trepanning

Removal of a core of metal by a hollow tool. May be performed by a hollow punch at forging temperatures or by a hollow cutting tool by machining at ambient temperatures.

Trim

The removal of the excess metal or flash produced during the forging process. The operation takes place in tools produced to the peripheral shape of the component, the component being pushed through the female impression by the identically-shaped male punch. The operation may be carried out hot or at room temperature.

Trim and punch

(1) A shearing operation to remove both an inner and an outer section of metal from a blocked or finished forging. (2) A combination of two operations whereby flash and punchout are removed simultaneously. The operation is generally performed on a trim press using a combination trim and punch die.

Trimmer

The combination of trimmer punch, trimmer blades, and perhaps trimmer shoe used to remove flash from a forging.

Trimmer blade

The portion of the trimmers through which the forging is pushed to shear off the flash. The shearing edge may be in more than one plane in order to fit the parting line of the forging.

Trimmer die

The upper portion of the trimmer that comes in contact with the forging and pushes it through the trimmer blades; the lower end of the trimmer punch is generally shaped to fit the surface of the forging against which it pushes. Also termed Trimmer punch.

Trimming press

A power press suitable for trimming flash from forgings.

Tryout

Preparatory run to check or test equipment, lubricant, stock, tools, or methods prior to a production run. Production tryout is run with tools previously approved; new die tryout is run with new tools not previously approved.

Tumbling

(1) The process for removing scale from forgings in a rotating container by means of impact with each other and abrasive particles and small bits of metal. (2) A process for removing scale and roughness from forgings by impact with each other, together with abrasive material in a rotating container.

Turning

Removing metal from the outside of a part by means of a tool in a lathe or similar machine tool.

Ultrasonic testing

A method of nondestructive testing of solid metal for internal flaws utilizing high-frequency sound waves.

Undercuts

Sections of a forging which, if driven into the impression while the metal is hot, would lock themselves into a die impression and prevent removal of the forging without distortion.

Underfill

A portion of a forging that has insufficient metal to give it the true shape of the impression.

UNS

The Unified Numbering System. A system that provides a means of correlating many nationally used numbering systems currently administered by societies, trade associations, and individual users and producers of metals and alloys, thereby avoiding confusion caused by use of more than one identification number for the same material. It also avoids having the same number assigned to two or more entirely different materials.

Upset forging

(1) A forging made by upsetting an appropriate length of bar, billet or bloom. (2) Working metal to increase the cross-sectional area of a portion or all of the stock. (3) A forging formed by heading or gathering the material by pressure upon hot or cold metal between dies operated in a horizontal plane.

Upsetter (Forging machine)

A horizontal forging machine where the workpiece is gripped between two grooved dies and deformed by a punch that exerts force on the end of the stock.

Vent

A small hole in a punch or die for admitting air to avoid suction holding or for relieving pockets of trapped air that would prevent die closure or action.

Vent mark

A small protrusion resulting from the entrance of metal into die vent holes.

Warm forging

Deformation at elevated temperatures below the recrystallization temperature. The flow stress and rate of strain hardening are reduced with increasing temperature; thus, lower forces are required than in cold working. For steel, the temperatures range from about 1000° F to just below the normal hot working range of 1900 to 2300° F. See also Cold Working and Hot Working.

Warpage

Term generally applied to distortion that results during quenching from heat-treating temperatures; hand straightening, press straightening, or cold restriking is employed, depending on the configuration of the part and the amount of warpage involved. The condition is governed by applicable straightness tolerances; beyond tolerances, warpage is defect and cause for rejection. The term is not to be confused with “bend” or “twist.”

Ways

The fitted V-shaped grooves in the ram and columns of a hammer or press that guide the descent and ascent of the ram.

Web

A relatively flat, thin portion of a forging, generally parallel to the forging plane—that connects ribs and bosses. See also Rib.

Wrought steel

A descriptive term for any particle of steel that has been produced by hot mechanical working.