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QUICK FACT GUIDES FOR MACHINISTS
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GUIDES
FUNDAMENTALS OF
DRILLING & TAPPING
FUNDAMENTALS
OF THREADING ON A LATHE
FUNDAMENTALS OF
WORKING BETWEEN CENTERS FUNDAMENTALS OF HEAT TREATING
FUNDAMENTALS
OF MILLING
FUNDAMENTALS
OF SAWING
METALWORKING
SHOP TERMS
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FORGING TERMS: AIR-LIFT
HAMMER: A type of gravity
drop hammer where the ram is raised for each stroke by an air cylinder. Since
length of stroke may be controlled, ram velocity and thus energy delivered to
the workpiece may be varied. ANVIL
(BASE): Extremely large,
heavy blocks of metal which supports the entire structure of conventional
gravity or steam driven forging hammers. Also, the block of metal on which hand
(or smith) forgings are made. ANVIL CAP:
See Sow Block. BACKDRAFT:
See Undercut. BAR:
A rolled or extruded metal product of uniform section usually circular,
rectangular or hexagonal. Bars are relatively smaller in cross section than
other forms of forging stock, such as billets. BAR END: See
End Loss. BASE:
See Anvil. BATCH-TYPE
FURNACE: A furnace for
heating materials in which the loading and unloading is done through a single
door or slot. BENDER: Term
denoting a die impression, tool or mechanical device designed to bend forging
stock to conform to the general configuration of die impressions subsequently to
be used. BILLET: A
semi-finished, hot rolled or continuous-cast metal product of uniform section,
usually rectangular with radiused corners. Billets are relatively larger than
bars. BLANK:
A piece of stock (also called a "slug" or "multiple") from
which a forging is to be made. BLAST
CLEANING (BLASTING): A
process for cleaning or finishing metal objects by use of an air jet or
centrifugal wheel which propels abrasive particles (grit, sand or shot) against
the surface of the workpiece at high velocity. BLOCKING:
A forging operation often used to impart an intermediate shape to a forging,
preparatory to forging of the final shape in the finishing impression of the
dies. Blocking can assure proper "working" of the material and
contribute to greater die life. BLOCKER-TYPE
FORGING: A forging which
approximates the general shape of the final part with relatively generous finish
allowance and radii. Such forgings are sometimes specified to reduce die costs
where only a small number of forgings are desired and the cost of machining each
part to its final shape is not excessive. BLOW: The
impact or force delivered by one work stoke of the forging equipment. BOARD HAMMER:
A type of gravity drop
hammer where wood boards attached to the ram are raised vertically by action of
counter-rotating rolls, then released. Energy for forging is obtained by the
mass and velocity of the freely falling ram and the attached upper die. BOSS:
A relatively short protrusion or projection on the surface of a forging, often
cylindrical in shape. BUSTER
(PRE-BLOCKING IMPRESSION): A
type of die impression sometimes used to combine preliminary forging operations
such as edging and fullering with the blocking operation to eliminate blows. CHARPY TEST: A
pendulum type impact test where the specimen is supported as a simple beam and
is notched opposite the point of impact. The energy required to break the beam
is used as an index of impact strength measurement. CHECK: A
crack in a die impression, generally due to forging pressure and/or excessive
die temperature. Die blocks too hard for the depth of the die impression have a
tendency to check or develop cracks in impression corners. CLEANING: The
process of removing scale, oxides or lubricants, acquired during heating for
forging or heat treating, form on the surface of the forging. See Blasting,
Pickling, Tumbling. CLOSED DIE
FORGING: See Impression
Die Forging. CLOSE
TOLERANCE FORGING: A forging
held to unusually close dimensional tolerances. Often little or n machining is
required after forging. COINING:
The process of applying necessary pressure to all or some portion of a forgings
surface in order to obtain closer tolerances, smoother surfaces or to eliminate
draft. Coining may be done while forgings are hot or cold and is usually
performed on surfaces parallel to the parting line of the forging. COINING DIES:
Dies in which coining or
sizing operations are performed. COLD HEADING:
Working metal at room temperature in such a manner that the cross-sectional area
of a portion or all of the stock is increased. COLD
INSPECTION: A visual
(usually final) inspection of the forgings for visible defects, dimensions,
weight, and surface condition at room temperature. The term may also be used to
describe certain non-destructive tests such as magnetic particle, dye penetrate
and sonic inspection. COLD SHUT:
A defect characterized by a fissure or lap on a forgings surface which has been
closed with out fusion during the forging operation. COLD
TRIMMING: Removing flash or
excess metal from the forging in a trimming press when the forging is at room
temperature. COLD WORKING:
Permanent plastic
deformation of a metal at a temperature below its recrystallization point, low
enough to produce strain hardening. CONVENTIONAL
FORGING: A forging
characterized by design complexity and tolerances which fall within the broad
range of general forging practice. COUNTERBLOW
FORGING EQUIPMENT: A
category of forging equipment wherein two opposed rams are activated
simultaneously, striking repeated blows on the workpiece at a midway point.
Action may be vertical, as in the case of counterblow forging hammers, or
horizontal with the "Impactor". COUNTERBLOCK:
A jog in mating surfaces of
dies to prevent lateral die shift caused by side thrust during forging of
irregularly shaped pieces. CROSS
FORGING: Preliminary working
of forging stock in flat dies to develop mechanical properties, particularly in
the center portions of heavy sections. CUTOFF:
A pair of blades positioned in dies or equipment (or a section of the die milled
to produce the same effect as inserted blades) used to separate the forging from
the bar after forging operations are completed.
(Used only when forgings are produced from relatively long bars instead of from
individual, pre-cut multiples or blanks). DIES: (DIE
BLOCKS): The metal block
into which forging impressions are machined and from which forgings are
produced. DIE SET: A
guided die holder to assure alignment of the dies during processing. DIE LAYOUT: The
transfer of the forging drawing or sketch dimensions to a template or die
surface for use in sinking dies. DIE LIFE: The
productive life of a die impression, usually measured in terms of the number of
forgings produced before the impression has worn beyond the permitted
tolerances. DIE
LUBRICANT: A compound
sprayed, swabbed or otherwise applied on die surfaces or forgings during forging
to reduce friction between the
forgings and the dies. Lubricants may also ease release of forgings from the
dies and provide thermal insulation. DIE MATCH:
The condition where dies, after having been set up in the forge equipment, are
in proper alignment relative to each other. DIE PROOF
(CAST): A casting of the die
impression made to confirm the exactness of the impression. DIE SHIFT: A
condition requiring correction where, after dies have been set up in the forging
equipment, displacement of a point in one die from the corresponding pint in the
opposite die occurs in a direction parallel to the fundamental parting lines of
the dies. DIESINKING:
The process of machining impressions in die blocks. DOWEL:
A metal insert placed between mating surfaces of the die shank and die holder in
the forging equipment to assure lengthwise die match. DRAFT: The
amount of taper on the sides of the forging necessary for removal of the
workpiece from the dies. Also, the corresponding taper on the side walls of the
die impressions. DRAFT ANGLE:
The angle of taper, expressed in degrees, given to the sides of the forging and
the side walls of the die impression. DRAWING:
A forging operation in which the cross section of forging stock is reduced and
the stock lengthened between flat or simple contour dies. See Fuller. DROP FORGING:
A forging produced by hammering metal in a drop hammer between dies containing
impressions designed to produce the desired shape. See Impression Die
Forging. DROP HAMMER: A
term generally applied to forging hammers wherein the energy for forging is
provided by gravity, steam or compressed air. See Air-Lift Hammer, Board
Hammer, Steam Hammer. DYE PENETRATE
TESTING: Inspection
procedures for detecting surface irregularities using penetrating liquids
containing dyes or fluorescent substances. See Zyglo. EDGER (EDGING
IMPRESSIONS): The portion of
the die impression which distributes metal, during forging, into areas where it
is most needed to facilitate filling the cavities of subsequent impressions to
be used in the forging sequence. See Fuller. ELASTIC
LIMIT: The maximum stress a
metal will withstand without permanent deformation. ELONGATION:
The amount of permanent stretch in a tensile test specimen before rupture. It is
usually expressed as a percentage of the original gauge length, such as 25
percent in 2 inches. END LOSS
(CROP END): Bar end left
over after cutting bar lengths of stock into forging multiples. See Multiple.
EXTRUSION: The
process of forcing metal to flow through a die orifice in the same direction
which energy is being applied (forward extrusion); or in the reverse direction
(backward extrusion) in which case the metal usually follows the contour of the
punch or moving forming tool. The extrusion principle is used in many impression
die forging applications. FILLET: The
concave intersection of two surfaces. In forging, the desired radius at the
concave intersection of two surface is usually specified. FINISH: The
material machined off the surface of a forging to produce the finish machine
component. Also, the surface condition of the component resulting from
machining. FINISH ALL
OVER (F.A.O.): Specification
designating that forgings musts be made sufficiently larger than the dimensions
shown to permit machining on all surfaces to a given size. FINISH
ALLOWANCE: Amount of stock
left on the surface of the forging for machining. FINISH
FORGING: See Conventional
Forging. FINISHER OR
FINISHING IMPRESSION: The
die impression which imparts the final shape to the forging. FLASH:
Necessary metal in excess of that required to completely fill the finishing
impression of the dies. Flash extends out from the body of the forging as a thin
plate at the line where the dies meet and is subsequently removed by trimming.
Cooling faster than the body of the component during forging, flash can serve to
restrict metal flow at the line where dies meet, thus assuring complete filling
of the finishing impression. FLASH
EXTENSION: Portion of flash
remaining after trimming. Flash extension is measured from the intersection of
the draft and flash on the body of the forging to the trimmed edge of the stock.
FLASH LAND:
Configuration in the finishing impression of the dies designed either to
restrict or encourage growth of flash at the parting line, whichever may be
required in a particular instance in order to assure complete filling of the
finish impression. FLASH LINE:
See Parting Line. FLAT DIE
FORGING (OPEN DIE FORGING):
Forging worked between flat or simple contour dies by repeated strokes and
manipulation of the workpiece. Also known as hand or smith" forging. FLOW LINES:
Patterns in a forging resulting from the elongation of nonhomogeneous
constituents and the grain structure of the material in the direction of working
during forging, usually revealed by macroetching. See Grain Flow. FORGEABILTIY:
Term used to describe the
relative ability of material to deform without rupture. FORGING: The
product of work on metal formed to a desired shape by impact or pressure in
hammers, forging machines (upsetters), presses, rolls and related forming
equipment. Forging hammers, counterblow equipment and high-energy-rate forging
machines impart impact to the workpiece, while most other types of forging
equipment impart squeeze pressure in shaping the stock. Some metals can be
forged at room temperature, but the majority of metals are made more plastic for
forging by heating. FORGING
MACHINES (UP-SETTERS OR HEADER):
A type of forging equipment, related to the mechanical press, in which the main
forming energy is applied horizontally to the workpiece which is gripped and
held by prior action of the dies. FORGING
PLANE: The plane which
includes the principal die face and which is perpendicular to the direction of
the ram travel. When parting surfaces of the dies are flat, the forging plane
coincides with the parting line. See Parting Line. FORGING
QUALITY: Term describing
stock of sufficiently superior quality to make it suitable for commercially
satisfactory forgings. FORMER: Part
of a master used in machining impressions in dies. See Master, Model,
Template. FOUNDATION:
The mass of structural material on which forging equipment is placed to
support the weight and to absorb residual energy of the forging operation. FRACTURE
TEST: Examination of the
broken surface of a test specimen or forging to determine the structure of the
metal or certain of its properties. FULLER
(FULLERING IMPRESSION): Portion
of the die which is used in hammer forging primarily to reduce the cross section
and lengthen a portion of the forging stock. The fullering impressions often
used in conjunction with an edger (or edging impression). GATE
(SPRUCE): A portion of the
die which has been removed by machining to permit a connection between multiple
impressions or between an impression and the bar. GATHERING
STOCK: Any operation whereby
the cross section of a portion of the stock is increased above its original
size. GRAIN: The
characteristic crystalline structural unit of metals as measured against an
accepted standard. GRAVITY
HAMMER: A class of forging
hammer wherein energy for forging is obtained by the mass and velocity of freely
falling ram and the attached upper die. Examples; board hammers and air-lift
hammers. GRINDING: Process
of removing metal by abrasion from bar or billet stock to prepare stock surfaces
for forging. Occasionally used to remove surface irregularities and flash from
forgings. GUTTER: A
slight depression machined around the periphery of an impression in the die
which allows space for the excess metal (flash) during forging. HAMMER
FORGING: Shaping of metal by
impact between dies in one of several types of equipment known as forging
hammers. See Air-Lift Hammers, Board Hammers, Counterblow Forging Equipment,
Steam Hammers. HAND FORGING:
See Flat Die Forging.
HANDLING
HOLES: Holes drilled in the
ends of forging die blocks to provide for handling by crane or bar. HEADER: See
Forging Machine. HEAT
(FORGING): Amount of forging
stock placed in a batch-type furnace at one time. HEAT OF
METAL: The quantity of
material manufactured from one melt at the metal producer's facility. Metal from
a single heat is extremely uniform in chemical analyses. HIGH-ENERGY-RATE
FORGING (HIGH VELOCITY OR HIGH SPEED FORGING): The
process of producing forgings on equipment capable of extremely high ram
velocities resulting from the sudden release of a compressed gas against a free
piston. HOG OUT:
A product machined from bar stock or from a hand forging rather than from an
impression die forging. The process is commonly known as "hogging out"
material. HOT
INSPECTION: An in-process
visual examination of forgings, using gages, templates or other non-destructive
inspection equipment to ensure quality. HOT STAMP: Impressing
markings in forging while the forging is in the heated, plastic condition. HOT TRIM: Removing
flash or excess metal from the forging in a trimming press while the forging is
in the heated state. HOT WORKING: The
mechanical working of metal at a temperature above its recreystallization point,
a temperature high enough to prevent strain hardening. IMPACT
EXTRUSION: A relative rapid
extrusion. See Extrusion. IMPRESSION:
A cavity machined into a forging die to produce a desired configuration in the
workpiece during forging. IMPRESSION
DIE FORGING: A forging that
is formed to the required shape and size by machined impressions in specially
prepared dies which exert 3-dimensional control on the workpiece. INCLUSION: Impurities
in metal, usually in the form of particles in mechanical mixture. INSERT: A
piece of steel which is removable from a die. The insert may be used to fill a
cavity, or to replace a portion of the die with a grade of steel better suited
for service at that point. INSERT DIE:
A relatively small die containing part or all of the impression of a forging,
and which is fastened to the master die block. INSPECTION: The
process of checking a forging for adherence to standards given in the
specifications. IRONING: (1)
A press operation used to obtain a more exact alignment of the various parts of
a forging, or to obtain a better surface condition: (2) An operation to increase
the length of a tube by reduction of wall thickness and out-side diameter. See Coining,
Swaging. IZOD TEST: A
pendulum type of impact test, in which the specimen is supported at one end as a
cantilever beam and the energy required to break off the free end is used as a
measure of impact strength. JOMINY:
A hardenability test for steel to determine degree of hardenability obtainable
by specified heat treatment. LAP: A
surface irregularity appearing as a seam, caused by the folding over of hot
metal, fins or sharp corners and by subsequent rolling or forging (but not
welding) of these into the surface. LAYOUT: The
checking of a forging to determine whether its dimensions are in accordance with
those given on the drawing or model. See Die Layout. LEAD PROOF:
See Die Proof.. LOCKS: Changes
in the plane of the mating faces of the dies. Locks aid in holding die alignment
during forging by counteracting lateral thrust which is present to an extent
dependent on the shape of the workpiece. MACHINE
FORGING (UPSETTER FORGING):
The process of forging in a forging machine (upsetter), in which the metals
moved into the die impression by pressure applied in a horizontal direction by
the moving die in the ram. MACHINING
ALLOWANCE: See Finish
Allowance. MACROETCH:
A testing procedure for conditions in metal, such as porosity, inclusion,
segregation's, carbonization, and flow lines from hot working. After applying a
suitable etching solution to the polished surface, the structure revealed by the
action of the reagent can be observed visually. MACROGRAPH: A
photographic reproduction of any object that has been magnified not more than 10
diameters. MACROSTRUCTURE:
The structure and internal condition of metals are revealed on a polished and
etched sample, examined either by the naked eye or under low magnification (up
to 10 diameters). MAGNAFLUX
TEST: See Magnetic
Particle Testing. MAGNETIC
PARTICLE TESTING: A
nondestructive test method of inspecting areas on or near the surface of ferro-magnetic
materials. The metal is magnetized, then iron powder is applied. The powder
adheres to lines of flux leakage revealing surface
and near-surface discontinuities. Magnetic particle testing is used for
both raw material acceptance testing and product inspection. Actual levels are
usually agreed upon in advance by forging producer and purchaser. MAGNAGLO: A
type of magnetic particle testing where the magnetic powder is fluorescent and
inspection is performed under black light. See Magnetic Particle Testing.
MARTEMPERING:
The process of quenching an austeniteied ferrous alloy in a medium at a
temperature in the upper portion of the temperature range of martensite
formation, or slightly above that range, and holding in the medium until the
temperature throughout the alloy is substantially uniform. The alloy is then
allowed to cool in air throughout the temperature range of martensite formation.
MASTER: Wood,
metal or plastic reproduction of one side of a proposed forged shape, used to
control cutters on tracer-controlled die sinking equipment. See Former, Master,
Plaster. MATCH:
A condition in which a point in one die-half is aligned properly with the
corresponding point in the opposite die-half within the specified tolerance. MATCHED EDGES
(MATCH LINES): Two edges of
the die face which are machined exactly at 90 degrees to each other and from
which all dimensions are taken in laying out the die impression and aligning the
dies in the forging equipment. MECHANICAL
PROPERTIES: Those properties
of a material which reveal the elastic and inelastic reaction when force is
applied, or that involve the relationship between stress and strain; for
example, the modules of elasticity, tensile strength and fatigue limit.
Mechanical properties are dependent on chemical composition, forging and heat
treatment. MECHANICAL
WORKING: Subjecting metal to
pressure, exerted by rolls, hammers or presses, in order to change the metal's
shape or physical properties. MICROSTRUCTURE:
The structure an internal
condition of metals as revealed on a ground and polished (and sometimes etched)
surface when observed at high magnification (over 10 diameters). MODEL: See
Former, Master, Plaster. MULTIPLE: A
piece of stock for forging which is cut from bar or billet lengths to provide
the exact amount of material needed for a single workpiece. NO-DRAFT
FORGING: A forging with
extremely close tolerances and little or no draft, requiring a minimum of
machining to produce the final part. Mechanical properties can be enhanced by
closer control of grain flow and retention of surface material in the final
component. NOTCH
SENSITIVITY: The reduction
in impact, endurance, or static strength of a metal, caused by stress
concentration as a result of scratches or other stress raisers on the surface. OPEN DIE
FORGING: See Flat Die
Forging. PARTING LINE:
The line along the surface
of a forging where the dies meet, or the line along the corresponding edge of
the die impression. PARTING
PLANE: The plane which
includes the fundamental parting lines of the dies; the dividing plane between
dies. See Forging Plane. PICKLING:
The process of removing oxide scale from forgings by treating in heated acid
bath. PLAN AREA
VIEW: The area of the plan
view of a forging; sometimes used to indicate the relative size of the forging. PLANSHING:
A finishing operation for the purpose of removing the trim line of forgings or
of obtaining closer tolerances. Usually done by rolling, pressing or hammering,
hot or cold. PLASTER:
A temporary model used to control a duplicating machine in die sinking or for
authenticating the accuracy of the dies. See Model. PLATTER: The
entire workpiece upon which the forging equipment performs work, including the
flash, spruce, tongholder and as many forgings as are made at one time. PREPARATION
CHARGE: A one-time charge
covering the cost of sinking dies and preparing required auxiliary tooling for
producing forgings to a particular design. In the usual practice of the forging
industry this charge conveys to the customer the exclusive right to purchase
forging produced on this tooling. The dies themselves are the property of the
forger, who also has the responsibility for maintaining and replacing the dies
as required for satisfactory production of forgings. PRESS
FORGING: The shaping of
metal between dies by mechanical or hydraulic pressure. Usually this is
accomplished with a single work stroke of the press for each die station. PROOF: Any
reproduction of a die impression in any material, frequently a lead or plaster
cast. See Die Proof. PROPORTIONAL
LIMIT: The greatest stress
that a material is capable of sustaining without a deviation from the law of
proportionality of stress to strain. PUNCH:
(1) The movable die in a trimming press or forging machine: (2) A tool used in
punching holes in metal. PUSHER
FURNACE: A continuous type
of furnace where stock to be heated is charged at one end, carried through one
or more heating zones and discharged at the opposite end. QUANTITY
TOLERANCE: Allowable
variation of quantity to be shipped on a purchase order. This tolerance is
properly agreed to by forging producer and purchaser when the order is placed. RAM: The
moving part of a forging hammer, forging machine, or press to which one of the
dies is fastened. REDUCTION OF
AREA: The difference, in a
tension test specimen, between the size of the original sectional area and that
of the area at the point of rupture. It is generally stated as a percentage of
the original area. REFRACTORY: Heat
resistant material, usually nonmetallic, used for furnace lining. RESTRIKING: Striking
a trimmed forging an additional blow in the dies in order to align or size its
several components or sections. The operation can be performed hot or cold. RING ROLLING:
The process of shaping weldless rings from pierced discs or thick-walled,
ring-shaped blanks between rolls which control wall thickness, ring diameter,
height and contour. ROLLER
(ROLLING IMPRESSION): The
portion of a forging die where cross sections are altered by hammering or
pressing while the workpiece is being rotated. ROLL FORGING:
The process of shaping stock between power driven rolls bearing contoured dies.
The workpiece is introduced from the delivery side of the roll, and is
reinserted for each succeeding pass. Usually used for performing, roll forging
is often employed to reduce thickness and increase length of stock. ROTARY
FURNACE: A circular furnace
constructed so that the hearth and workpieces rotate around the furnaces axis
during heating. SADDLING
(MANDREL FORGING): The
process of rolling and forging a pierced disc of stock over a mandrel in order
to produce a weldless ring. SAND
BLASTING: The process of
cleaning forgings by propelling sand against them at high velocity, See Blast
Cleaning. SCALE:
The oxide film that is formed on forgings, or other heated metal, by chemical
action of the surface metal with the oxygen in the air. SCALE PIT: A
surface depression formed on the forging due to scale remaining in the dies
during the forging operation. SEAM:
A crack or inclusion on the surface of forging stock which may carry through
forging and appear on the finished product. SEMI-FINISHER
(SEMI-FINISHING IMPRESSION):
An impression in the forging die which only approximates the finished dimensions
of the forging. Semi-finishers are often used to extend die life on the
finishing impression; to assure proper control of grain flow during forging; and
assist in obtaining desired tolerance. SHANK:
The portion of the die or tool by which it is held in position in the forging
unit. SHEARING: A
process of mechanically cutting metal bars to proper stock length necessary for
forging the desired product. SHOE: A
holder used as a support for the stationary portions of trimming and forming
dies; sometimes termed Saw Block. SHOTBLASTING:
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 Blast
Cleaning. SHRINKAGE: The
contraction of metal during cooling after forging. Die impressions are made
oversize according to precise shrinkage scales to allow forgings to shrink to
designed dimensions and tolerances. SHRINK SCALE:
A measuring scale or rule, used in die layout, on which graduations are expanded
to compensate for thermal contraction (shrinkage) or forging during cooling. SIZING:
A process employed to control precisely a diameter of rings or tubular
components. SLOT FURNACE:
A common batch-type forge
furnace where stock is charged and removed through a slot or opening. SLUG: (1)
Metal removed when punching a hole in a forging. Also termed punch out:
(2) Forging stock for one workpiece cut to length. See Blank. SMITH
FORGING: See Flat Die
Forging. SNAG GRINDING
(SNAGGING): The process of
removing portions of forgings not desired in the finished product, by grinding. SOAKING: A
heating process during which metal is held at an elevated temperature for the
length of time sufficient for attainment of uniform temperature throughout the
material, or for homogenization of elements. SOLUTION HEAT
TREATMENT: A process in
which an alloy is heated to a suitable temperature, is held at this temperature
long enough to allow a certain constituent to enter into solid solution and is
then cooled rapidly to hold the constituent in solution. The metal is left in a
supersaturated, unstable state and may subsequently exhibit age hardening. SONIC
TESTING: See Ultrasonic
Testing. SOW BLOCK: Metal
die holder employed in a forging hammer to protect the hammer anvil from shock
and wear. Also called Anvil Cap or Shoe. Sow blocks are
occasionally used to hold insert dies. 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 stoke may be varied. STOCK: Raw
material used to produce forgings. STRAIGHTENING:
A finishing operation for
correcting, within specified tolerances, the misalignment in a forging or
between various sections of a forging often caused by heat treatment.
Straightening may be done by hand, with simple tools, or in a die in forging
equipment. STRIKING
SURFACE: Those areas on the
face of a set of dies which are designed to meet when the upper die and lower
die are brought together. Striking surface help protect impressions from impact
shock and aids in maintaining longer die life. Also termed Beating Area. SURFACE
PEENING (SHOT PEENING): The
process of severe shotblasting to increase the fatigue life of forgings. SWAGE
(SWAGED): Operation of
reducing or changing the cross sectional area by revolving the stock under rapid
impact blows. SWEDGE:
See Swage. TEMPLATE: A
gage or pattern usually made from sheet metal. Templates are used to check
dimensions on forgings and as an aid in sinking die impressions. See Former,
Master, Pattern. TENSILE
PROPERTIES: The mechanical
property data obtained from tensile test on a metal specimen, including tensile
strength, elongation, reduction of area and yield point THERMAL
STRESS: Stress in metal
resulting from the non-uniform distribution o heat. TONGHOLD: The
portion of the stock by which the operator grips the stock with tongs during
forging. TOUGHNESS:
Ability of a metal to absorb energy without failure. Toughness may be expressed
as the total area under the stress-strain curve. TRIMMER
PUNCH: The upper portion of
the trimmers which come 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. TRIMMERS:
The combination of trimmer punch, trimmer blades and perhaps trimmer shoe used
to remove the flash from forgings. TRIMMING: The
process of removing flash or excess metal from a forging. TRIMMING SHOE
(TRIMMING CHAIR): The holder
used to support the trimmer. TUMBLING: The
process for removing scale from forgings in a rotating container by means of
impact with each other, abrasive particles and small bits of metal. Tumbling can
produce a variety of surface finishes depending on the tumbling agents used. ULTRASONIC
TESTING: A non-destructive
test applied to sound-conductive materials having elastic properties for the
purpose of locating nonhomogeneities or structural discontinuities within a
material by means of ultrasonic impulses (inaudible high-frequency sound waves).
UNDERCUT: A
section of a forging or die contour with reverse taper. Stock driven into such a
die contour would lock itself into the impression and prevent removal of the
forging without distortion. Also known as Backdraft. UNDERFILL:
A portion of a forging which has insufficient metal to give it the true shape of
the impression. UPSET
FORGING: A forging obtained
by upset of a suitable length of bar, billet or bloom. UPSETTING:
Working metal in such a manner that the cross-sectional area of a portion or all
of the stock is increased. YIELD POINT: The
level or degree of stress in a material at which there occurs a marked increase
in strain without an increase in stress. YIELD
STRENGTH: The stress at
which a material exhibits a specified limit of permanent stern; often maximum
unit load with a 0.2 percent deviation from a proportional stress-strain
relation. ZYGLO: A
method for non-destructive surface inspection of primarily non-magnetic
materials using fluorescent penetrants. |
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Copyright © 2002 QUICK FACT GUIDES FOR MACHINISTS
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