McGuire Glossary of Fastener Terminology

T - 207 terms

T-HEAD BOLTS - Familiar T-Head design for flush channel assembly.

T-SLOTS - Slots created by machines which are located in the lower bolster and upper slide, that provides a means for attaching die components. T-Slots can be customized in accordance with client specifications.

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.

TAKT TIME - Takt Time is the available production time divided by the rate of customer demand. Takt time becomes the heartbeat of any lean organization. Takt is a German term for rhythm.

TAMPER-RESISTANCE DRIVES - Tamper-resistant drives are commonly used to prevent easy access thereby reducing the incidence of damage, improper repairs or repairs by people without the relevant technical knowledge to a wide variety of equipment. The list of tamper-resistant drives is fairly long and continues to grow. This Glossary highlights many that are known at this time and will probably grow in the coming year(s).

TANGENT PIN - A pin intersecting the periphery of the tool or die bore normal to the axis of the bore and used to hold in a sliding tool or die or a maintain radial orientation of the tool or die.

TANK BOLTS - Truss Slot machine screws used in plumbing and wooden vat construction

TANTALUM - A gray ductile metal with a high melting point and excellent corrosion resistance against chemicals.

TAP - To cut threads in a hole with a rotating tool called a 'Tap' having threads on it and fluted to give gutting edges.

TAPER - Taper, as used for fasteners, is the angle between one side and the axis of the fastener. Taper may refer to the head, shank, or some other feature of a fastener.

TAPERED INSERT - An insert design where the outside diameter of the insert is not parallel to the axis of the insert but is tapered towards the front of the insert.

TAPPED HOLE - A threaded hole in a part

TAPPING - Operation to create internal threads by either cutting or forming.

TARGET MACHINING - Incorporating a (target benchmark of gage point) on a forging to facilitate machining; coined locating surfaces and drilled centers are commonly used.

TARNISH - The dulling, staining or discoloration of metal due to superficial corrosion. The film so formed

TARNISH, TARNISHING - (1) The dulling, staining, or discolouration of metals due to superficial corrosion (2) the film so formed.

TC - Total number of coils in a spring

TEFZEL(R) (ETFE) (PLASTICS) - Ethylene-tetrafluoroethylene copolymer is a high impact material with properties similar to ECTFE. It is commonly used to manufacture pumps, valves, computer housings, and other electrical components.

TEMPER - The state of a metal or alloy involving its structure and mechanical properties. Temper varies from the annealed temper(soft) to spring temper.

TEMPER - A heat treatment process that occurs after quenching. Forgings are heated below critical temperatures and then cooled to relieve stresses caused by quenching. This process helps the forging obtain specific mechanical properties.

TEMPER BRITTLENESS - Brittleness that results when certain steels are held within, or are cooled slowly through, a certain range of temperatures below the transformation range. The brittleness is revealed by notched-bar impact tests at or below room temperatures.

TEMPER CARBON - The free or graphic carbon that comes out of solution usually in the form of rounded nodules in the structure during Graphitizing or Malleablizing.

TEMPERATURE (FORGING) - The temperature of the forging stock just prior to forging.

TEMPERING - Reheating a quench-hardened or normalized ferrous alloy to a temperature below the transformation range and then cooling at any rate desired. This gives it its final tensile strength and hardness. It is done to 'toughen' the metal. Tempering is a stress relieving process.

TEMPERING - Heating a quench-hardened or normalized ferrous alloy to a temperature below the transformation range to produce desired changes in properties.

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.

TENSILE LOAD - The load applied to a fastener along its length.

TENSILE PROPERTIES - The mechanical properties of a metal when subject to tension. These properties including tensile strength, yield strength, elongation, proportional limit, and reduction of area.

TENSILE STRENGTH - The maximum load per unit of original cross-sectional area obtained before rupture of a tensile specimen. The ultimate strength of a given, material, alloy, or product that determines the peak load it can withstand before breaking. It is determined by performing a tension test and observing the maximum load attained. Usually expressed in pounds or Newtons.

TENSILE STRENGTH - An index of the quality of a material through a mathematical expression which divides the material's load capacity in tension by its original cross-sectional area. Particularly accurate for spring steels, as there is only a small difference between ultimate tensile strength and yield strength.

TENSILE STRESS AREA - The effective cross section area through the threaded section which resists bolt fracture in tension. There are a variety of different methods used to calculate the tensile stress area. All these methods use the PD and/or the minor diameter as the basis for the calculation.

TENSILE STRESS AREA - The amount of force applied on the stress area of a thread. Fine threads have a greater tensile stress area than coarse threads.

TENSION FASTENER - A fastener whose primary function is to resist forces which tend to elongate it.

TENSION JOINT - A joint with forces acting parallel to the fastener's axis.

TEST REPORT - A written or electronic document provided by the authorized party to certify that a tested fastener's chemical and mechanical properties conform to the specification required.

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

THERMAL EXCURSIONS - If the joint and fasteners are different materials, differential thermal expansion and contraction can cause tightening or loosening.

THERMAL EXPANSION - An increase in the volume of the bolt or joint when heated.

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.

THERMOPLASTIC - Polymers characterized by their ductility (fillers may be added to increase stiffness or other characteristics). Thermoplastics can be re-melted and reformed several times without degrading the material.

THERMOSET - These polymers are characterized by extreme stiffness. The initial molding process causes a chemical reaction which "cures" the material, so the resin cannot be reprocessed.

THICK WAL - A style of part having a wall thickness of rounghly 14% of sthe counterbore diameter. Thick wall parts have higher installation loads and typically cn not be installed with spin-spin tools. Although they have narrower grip ranges than thin wall parts, they provide a higher level of performance.

THICKNESS (SPRING TERM) - Thickness of rectangular or side of square material.

THICKNESS OF THREAD - The distance between the flanks of the thread measured at a specified position and parallel to the axis.

THIEF - An auxiliary cathode so placed as to divert to itself some current from portions of the article which would otherwise receive too high a current density.

THIN WALL - A style of part having a wall thikness of rouhgly 8% of the counterbore diameter. Thin wall parts haver lower installation loads sllowing them to be installed with spin-spin tools. They also have wider grip ranges than thick wall parts, but provide a lower level of performance.

THREAD - A ridge of uniform section in the form of a helix on the external or internal surface of a cylinder. This is known as a straight or parallel thread to distinguish it from a taper thread which is formed on a cone or frustum of a cone.

THREAD - The thread us the inclined plane that wraps around the cylinder of the fastener; a ridge of uniform section in the form of a helix on the external or internal surface of a cylinder.

THREAD CREST - The top part of the thread. For external threads, the crest is the region of the thread which is on it's outer surface, for internal threads it is the region which forms the inner diameter.

THREAD CUTTING - A method of producing screw threads that generally uses a single-point tool to cut a blank or workpiece as it rotates on a lathe.

THREAD ENGAGEMENT - The percentage of the thread height that is in the material being fastened.

THREAD FILLER - A special filler screwed into the back of a tapered insert design case. This filler is used to keep the tapered inserts in position with axial pressure.

THREAD FIT - The set of allowances and tolerances that determines the degree of tightness or looseness between mating components.

THREAD FLANK - The thread flank joins the thread roots to the crest.

THREAD FORM - The shape or profile of a thread. Thread forms include V or square threads.

THREAD FORM - Defined as the profile of an axial section through one complete pitch. Basic form for Unified National and M Profile threads is a 30 degree flank angle with a P over 8 truncation at the major diameter and a P over 4 truncation at the minor diameter. Design forms for internal and external threads are different from each other, maybe slightly different from the basic form and represent maximum material conditions.

THREAD GALLING - The displacement of material between mating threads during tightening, which causes contact points to shear, producing friction, increased resistance to tightening and even seizing of the threads. Thread galling is most common with fasteners made of materials that self-generate an oxide surface film such as stainless steel.

THREAD HEIGHT - This is the distance between the minor and major diameters of the thread measured radially.

THREAD LENGTH - The length of threads on a fastener. There are formulas for standard fasteners and then there are special lengths determined by applications.

THREAD MILL - Cutters used in CNC milling machines to produce internal and external threads in a workpiece.

THREAD PITCH - The distance between corresponding points such as root to root or crest to crest on adjacent threads. Used to designate threads in the Metric system. The inverse of the YTPI is the pitch.

THREAD PROFILE, THREAD FORM - The configuration of the thread in an axial plane. A thread has three parts: the crest, root, and flanks. Common thread forms UN, UNR, and UNJ.

THREAD ROLLING - A cold-forging process whereby screw threads are formed by displacement of metal as opposed to cutting. The process is usually used for producing external threads and is seldom practical for small quantities.

THREAD ROLLING - A method of forming external threads on a blank buy squeezing the part between two forming dies. In flat die forming, one of the dies is stationary and fastened to the bed of the machine. The other die is mounted to a reciprocating slide.

THREAD ROLLING DIE - A component that shapes metal using extreme pressure into grooved rollers to form threads.

THREAD ROOT - The thread root is the bottom of the thread, on external threads the roots are usually rounded so that fatigue performance is improved.

THREAD RUNOUT - The portion at the end of a threaded shank which is not cut or rolled to full depth, but which provides a transition between full depth threads and the fastener shank or head.

THREAD SERIES - Groups of diameter-pitch combinations distinguished from each other by the number of threads per inch applied to a specific diameter. Three common series: UNC, UNF, and 8-UN.

THREAD TOLERANCE - The slight variation between the theoretically perfect threads and the unit of actual production that is allowed and expected. The total amount by which a specific dimension is permitted to vary.

THREADED FASTENING SYSTEM - An assembled combination of a fastener, an internally threaded part such as a nut or an insert, and also the region of all parts clamped between them, including washers, compressed by the fastener preload.

THREADED INSERT - A metal fastener usukally threaded, that can provide a strong attachment point to a section of material. Threaded inserts can provide strong threads to soft materials such as platics or composites. Other stype of threaded inserts can be clinched or may utilize blind threaded rivet technology to provide strong threads in thin metal sheets. The use of threaded inserts eliminates the need for tapping or otherwise creating threads directly into the base material which may not offer the strength required or in some cases may be more costly.

THREADLOCKER - Anaerobic Adhesives applied to fastener threads.

THREADS - (1) Pitch diameter - Generally used as the thread rolling diameter for machine screw threads. (2) Major diameter - The outside diameter of the threads. (3) Minor diameter - The smallest diameter or (root) diameter for the thread.

THREADS PER INCH (TPI) - The number of threads contained in one inch of a threaded fastener's length. Used to designate threads in the Unified System. The inverse of the pitch is the TPI.

THROAT (GAP) - An open space in the press frame that allows for the positing of material in the workspace. It is located behind the slide center line.

THROUGH HARDENED - A process to increase uniform material hardness.

THROUGHHOLE - A hole threaded or unthreaded, which transverses the entire length of a part and is usable from either end.

THROWING POWER - The property of a solution to obtain an even distribution of the coating on an article of complex shape.

THRUST LOAD CAPACITY (PG) OR (PR) - Overall capacity of an assembly to withstand a given value of thrust load in pounds, The limitation being the lesser of two mathematical calculations: ring thrust load capacity (PR) or groove thrust load capacity (PG).

THUMBSCREW - Thumbscrew is a type of screw drive with either a tall head and ridged or knurled sides, or a key-like flat sided vertical head. They are intended to be tightened and loosened by hand, and not found in structural applications. ASME 18.6.8 covers dimensions for Type A (shoulder under the head), regular or heavy, along with Type B (without shoulder), regular and heavy.

TIE ROD - A steel rod which is threaded at both ends and utilized for trying sections of dies together or for repairing broken dies. These rods are stretched to place members under a predetermined compressive load.

TIMED AIR - Special machining to allow for the introduction of timed compressed air directly into the tool or die. Used to blow a pierced slug off a piercing punch.

TIMED HOLD - The first portion of the TKO motion in the heading slide. During this part of the stroke, the dimension from the face of the die to the face of the TKO lever or rod stays the same. The majority of the formed part should be removed from the tool during this part of the stroke.

TIN - A malleable and ductile metal which increases strength, hardness and corrosion resistance against salt water when added to brass alloys.

TIN, ELECTROPLATED - Silver gray in color. Excellent corrosion protection for fasteners in contact with food. Improves lubricity on steel fasteners.

TIN/ZINC ALLOY ELECTROPLATING - Tin/zinc alloy coatings (typically 70 percent tin and 30 percent zinc) are applied to threaded fasteners to provide a corrosion resistant coating. One of the advantages of such coatings is that bimetallic corrosion will not occur when placed into contact with such metals as aluminum or steel.

TINY FINISHWORK HEAD - The tiny finishwork head has been specifically engineered to be almost invisible when mounted, without compromising strength of the head or screw. The head size fits with concealed mounting tools.

TIR OR T.I.R. - An abbreviation for (Total Indicator Reading). This is used to indicate the amount of runout between formed surfaces.

TITANIUM - A silver gray metal with high corrosion resistance against salt waters, chlorides, and many acids. It is strong and lightweight. High strength to weight ratio, temperature swings from subzero to 600 degrees F. Grade 5 is about 4x stronger than steel but 45 percent lighter.

TITANIUM NITRIDE BIT - These bits have a rough surface crating millions of micro gripping points. The Titanium coating provides an extra hard surface over the gripping points to protect them during use. The increase in roughness grips the entire recess of the screw and reduces cam out.

TKO OR T.K.O. - An abbreviation for (Timed Kickout). This is the part ejection mechanism on the machine heading slide. It is used to remove parts from the tools after forming.

TNAK VOLTAGE - The total potential difference between the anode and cathode of an electroplating bath or electrolytic cell during electrolysis.

TOLERANCE - The absolute amount of maximum or minimum dimensional deviation allowed that will not affect the performance of a mechanical part. The total amount of variation permitted on the size of a dimension. When min. and mx. dimensions are given, tolerance is the difference between the two. Internal threads are tolerance above basic dimensions and external threads are tolerance below basic dimensions.

TOLERANCE - Permissible variation from a specification for any characteristic of the product.

TOLERANCE - The permissible deviation from a specification for any design characteristic.

TOLERANCE CLASS - A combination of tolerance grade and a fundamental deviation which is given to an internal or external thread. A tolerance class for an internal thread when combined with the tolerance class for an external thread gives the class of fit for mating threads.

TOLERANCE GRADE - The difference between maximum and minimum metal conditions for a tolerance applied to a screw thread. For metric threads the tolerance grade is given a number.

TOLERANCE LIMIT - The variation, positive or negative, by which a size is permitted to depart from the design size.

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.

TONNAGE - The counteracting force exerted by the press against the workpiece in the die. The tonnage rating capacity of the machine is specified at a distance above the bottom of the stroke of the slide.

TOOL - A general term used to describe a heading tool or punch carried on the heading slide as compared to a stationary die. Often (Tooling) refers to a complete die set.

TOOL & DIE - Precision tools or metal forms that are utilized to cut, shape and form metals. They may include molds, holding down devices, stamping or drilling tools, as well as gauges and other measuring devices.

TOOL CAP - This is a removable portion of the tool holder on the FORMAX and FORMAX PLUS machines. It allows for the quick changing form one style of tool holder to another and still maintaining the centering of that tool holder.

TOOL CHANGER - The component of a CNC machine center that stores and automatically switches between multiple tools.

TOOL HOLDER - This is the machine part fastened to the face of the heading slide that holds the moving tooling components.

TOOL SLIDE - The linear distance a sliding tool must move to allow for the backward extrusion of a hole, piercing, or the upsetting of a preform.

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.

TOOLPAK - The punch side assembly of the Formapak on FORMAX & FORMAX PLUS machines. It includes the tool holders and wedges.

TOP DEAD CENTER (TDC) - The uppermost point on a slide, that is, when the press is at the top of the stroke.

TOP FEED - A method of automatic installation in which the fastener to be isntalled is presented automatically to the pulnch.

TORLON(R) (PAI) (PLASTICS) - Polyamide-imide possesses a combination of great mechanical strength, the ability to withstand radiation, usability from approoximately -300F to 500F, and resistance to most chemicals at room temperature. It is also flame retardant and gives off almost no smoke when burned. It is available in unreinforced grades and is readily machinable. This combination of assets makes it a good metal substitute for aerospace and electronic applications. It is commonly used for bushings, seals and distributors in engines and machinery.

TORQ-SET - TORQ-SET is a cruciform screw drive used in torque-sensitive applications. The Torq-Set head is similar in appearance to a Phillips drive in that it has a cross with 4 arms. In Torq-Set however, the lines are offset from each other, so they do not align to form intersecting slots across the top of the head. Because of this, a regular Phillips or flat-blade screwdriver will not fit the head. It is used in military and aerospace applications. The National Aerospace Standard is NASM 33781 and the NASM 14191 standard for the ribbed version (ACR Torq-Set).

TORQSPLINE® LEAD SCREWS - A power screw series characterized by the use of multiple start threads to produce very fast linear motion. Torqspline screws have a minimum of 4 starts and a lead greater than the diameter of the screw.

TORQUE - A twisting force that causes the rotation of a shaft or will set up a twist in a stationary shaft and is generally expressed in foot pounds or inch pounds. Metric fasteners are measured in newton-metres (Nm).

TORQUE - A rotational moment; it is a measure of how much twisting is applied to a fastener. The units used to measure torque are in the form of force times length. Usually measured in newton-metres (Nm) if metric units are used or pounds feet (Lb-ft) when imperial unites are used.

TORQUE - (Also known as Moment) The product of the distance from the spring axis to the point of load application and the force component normal to the distance line. Usually expressed in N.mm

TORQUE FORCE - SET SCREWS - The compressive force developed at the point depends on lubrication, finish and, material.

TORQUE OR MOMENT (SPRING TERM) - A twisting action in torsion springs which tends to produce rotation, equal to the load multiplied by the distance (of moment arm) from the load to the axis of the spring body. Usually expressed in inch pounds (in/lbs.) or Newton millimeters (N/mm).

TORQUE WRENCH - A manual wrench which incorporates a gauge or other method to indicate the amount of torque transferred to the nut or bolt.

TORQUE-OUT - The amount of torque necessary to spin the fastener out of the sheet. The torsional holding power of a self-clinching fastener in a sheet. Torque-out testing is conducted by applying pure tension (no axial load) to the self-clinching fastener.

TORQUE-THRU - An indirect measure of the tensile strength of a self-clinching fastener. The term torque-thru is most applied to studs. Torque-thru tests on studs are conducted by placing a bushing over the stud, applying a nut, and tightening until failure results from the induced tensile load exceeding the tensile strength of the stud.

TORQUE-TO-TURN - Typically the torque required to rotate the installed fastener in the application material, usually applies to threaded inserts.

TORSION SPRING - A spring that is rotated offering resistance to externally applied torque. Ends can vary in length and be bent.

TORSION SPRING - A helical spring which provides rotational energy or torque. The material is such a spring is stressed in bending. A torsion spring can have two separate sets of coils in which case it is known as a double torsion spring.

TORSION ZONE - In a true torsion bit this is the reduced diameter section of the shank between the hex body and tip. This area absorbs torque during impact extending the life of the bit.

TORSIONAL STRENGTH - A load expressed in terms of torque, at which the fastener fails by being twisted until it fractures.

TORX - A hexalobular socket drive for better cam-out resistance, extended bit life and reduced operator fatigue.

TORX - The hexalobular socket screw drive, often referred to the name of star drive, uses a star-shaped recess in the fastener with six rounded points. It was designed to permit increased torque transfer from the driver to the bit compared to other drive systems. Torx is very popular in the automotive and electronics industries because of resistance to cam-out, and extended bit life, as well as reduced operator fatigue by minimizing the need to bear down on the drive tool to prevent cam out.

TORX PLUS - Torx-Plus is an improved version of Torx that extends the tool life even further and permits greater torque transfer compared to Torx. An External Torx version exists, where the screw head has the shape of a Torx screwdriver bit, and a Torx socket us used to drive it.

TORX PLUS TAMPER-RESISTANCE - This is a tamper-resistant variant of Torx Plus, sometimes called Torx Plus Security, is a five-lobed variant, with a center post. It is used for security as the drivers are uncommon.

TORX TTAP - Torx ttap is a version of Torx that reduces wobbling between the fastener and the tool, and is backward compatible with standard hexalobular tools.

TOTAL HOLD - This is the addition of the timed hold and untimed hold movements during the TKO stroke. The tooling needs to be designed to accommodate the total hold value selected.

TOTAL NUMBER OF COILS - The total of all active and inactive coils.

TOTAL THREAD - The total thread includes the complete or effective thread and the incomplete thread.

TOUGHNESS - The ability of a material to absorb considerable energy (impact or shock loading) without fracturing.

TPI THREADS PER INCH - The number of threads contained in one inch of a threaded fastener's length. Used to designate threads in the Unified System. The inverse of the pitch is the TPI.

TRACEABILITY - The capability of authenticate manufacturing history by documentation of raw materials, heat number, locations, or application of the product.

TRACEABILITY - Is the path by which a measurement can be traced back to the source from which it is derived, such as NIST in the United States. Direct traceability implies that the laboratory has its primary masters calibrated directly by such an agency for reduced measurement uncertainty.

TRANSFER ASSIST - A machine mechanism that is mounted below the die block. It raises and lowers a support tip that keeps the formed part from falling during the kickout stroke until the transfer fingers can grip the part. Primarily used with straight across transfers and formed parts that had multiple steps or tapers on the outside diameter.

TRANSFER CORRIDOR - The theoretical space that the transfer fingers move through from station to station. It is important that any tooling items do not infringe on the corridor during the transfer movement.

TRANSFER DIE - Variation of a progressive die where the part is transferred from station to station by a mechanical system. Mainly used where the part has to be free from the strip to allow operations to be performed in a free state.

TRANSFER DIE STAMPING - Transfer die stamping operations are the same as progressive die stamping operations except the sheet metal blank is separated early and transferred along a conveyor belt or similar structure.

TRANSFORMATION RANGES - Those ranges of temperature within which austenite forms during heating and transforms during cooling. The two ranges are distinct, sometimes overlapping but never coinciding. The limiting temperatures of the ranges depend on the composition of the alloy and on the rate of change of temperature, a particularly during cooling.

TRANSFORMATION TEMPERATURE - The temperature at which a change in phase occurs. The term is sometimes used to denote the limiting temperature of a transformation range. The following symbols are used for iron and steels: Accm = in hypereutectoid steel, the temperature at which the solution of cementite in austenite is completed during heating. Ac1 = The temperature at which austenite begins to form during heating. Ac3 = The temperature at which transformation of ferrite to austenite is completed during heating. Arcm = In hypereutectoid steel, the temperature at which precipitation of cementite starts during cooling. Ar1 = The temperature at which transformation of austenite to ferrite or to ferrite plus cementite is completed during cooling. Ar3 = The temperature at which austenite begins to transform to ferrite during cooling. Ar4 = The temperature at which delta ferrite transforms to austenite during cooling. Ms = The temperature at which transformation of austenite to martensite starts during cooling. Mf = The temperature, during cooling, at which transformation of austenite to martensite is substantially completed. All these changes except the formation of martensite, occur at lower temperatures during cooling than during heating, and depend on the rate of change of temperature.

TRAP - A condition where an incoming blank or tooling item forms an enclosed cavity that does not allow the escape of oil or air from that cavity.

TRAPPED EXTRUSION - This refers to a forward extrusion where the incoming blank is totally enclosed inside the tooling before the extrusion takes place.

TREES - Branched or irregular projections formed on a cathode during electrodeposition, especially at edges and other high current density areas.

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.

TRI-ANGLE DRIVE - The TA is a type of screw drive that used a triangle-shaped recess in the screw head. This drive can restrict access to the device internals but can readily be driven with hex keys. The sides of the triangle are straight, which differs from the Tri-Point-3 fastener drive.

TRI-GROOVE DRIVE - Tri-Groove or T-Groove is a design for a security screw with a flat-topped conical head and three short radial slots that do not join in the center.

TRI-POINT DRIVE - The TP (or Y-Type) security screw drive is similar to the Phillips screw head, but with three points rather than four. Often used in electronics.

TRI-POINT-3 DRIVE - tp3 (sometimes referred to as Tri-Lobe or Tri-Lobular) uses a Reuleaux triangle-shaped recess in the screw head , to make it semi-secure because it cannot be driven by a flat-blade screwdriver and is not readily driven, as Tri-Angle is by hex keys. There are four sizes available in Metric.

TRI-WING DRIVE - The TRI-WING, also known as Triangular Slotted, is a screw with three slotted "wings" and a small triangular hole in the center. Unlike the "tri-point" fastener, the slots are offset, and do not intersect the center of the fastener. A version with left-hand threads is called an OPSIT screw, where unscrewing can be done by turning the screwdriver tool clockwise, which is opposite the tri-wing and regular screws. Tri-Wing fasteners are used as a primary fastener on commercial aircraft.

TRIAGE - A system used to sort workloads into categories in a service environment. This method facilitates prioritization of the workloads by urgency, level of difficulty, or length of activity, to reduce delays in performing the service.

TRILOBULAR™ SCREWS - Developed specifically for plastics. Deep wide spaced threads in a tri-lobular form. Several tradename fasteners for these types of screws and applications.

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 - A metal removal process where the excess metal is sheared from the outside surface of the part. (Example: to trim the hex shape on a bolt blank). (1) BOLTMAKER (pinch) TRIM - The metal is sheared from the outside of a button upset and formed into a trim chip between the trim punch and die. A machine mechanism provides a bump kick through the die kickout pin to shear off the trim chip. (2) HEX FLANGE BOLT (crush) TRIM - The metal is sheared from the outside of a preform upset and formed into the flange. The outside of the flange is trimmed in a subsequent BOLTMAKER TRIM operation. (3) PUSH THRU TRIM - The formed blank is pushed through a die insert and the outside surface is trimmed from the part. No trim kick mechanism is required.

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.

TRIM CHIP - See Scrap

TRIM DIE - The tooling component that shears the metal during the trim operation.

TRIM HEADS - Similar to the 82 degrees flat and oval head machine screws except that the size of the head for a given size screw is one or two sizes smaller than the regular flat and oval sizes.

TRIM KICK - A positive mechanical die kick motion at or slightly after dead center to and used to shear off the trim kick.

TRIM PAK - A special Toolpak for FORMAX & FORMAX Plus machines with a special trim discharge wedge in the last station that discharges the trimmed parts under the heading slide.

TRIM PUNCH - The stationary component of the trim tooling typically mounted in the die blcok.

TRIM TUBE - The tube in the heading slide on traditional machines that guides the trimmed parts from the heading slide to the pointer.

TRIMMED-KNURL - When a knurl platform is knurled in screw machine work, the knurl rolls over or overhanges the platform. Knurls may be trimmed flush with the platform (-O S type nuts) trimmed to some value slightly greater than the platform height (-1 and -2 S Type nuts) or may be left untrimmed (type R retainlers).

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 contrast 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 - The term applied to the process of shaping or sizing by forcing a part through a die of desired size and shape.

TRIMMING PRESS - A power press suitable for trimming flash from forgings.

TRIPLE-SQUARE (XZN) - The Triple-square is a type of screw drive with 12 equally spaced protrusions, each ending in a 90 degree internal angle. The drive comes from overlaying three equal squares to form such a pattern with 12 right-angled protrusions (a 12-point star). The idea being that it resembles a square (Robertson) drive but can be engaged at more frequent angles by the driver bit. Bits available in 10 sizes. Triple-square drive fasteners have been used in high-torque applications. The fasteners involved have been hardened and tempered to withstand the driving torque without destroying the star points.

TRIPOLI - Friable and dust like silica used as an abrasive.

TRIVALENT ZINC CHROMATE PLATING - Zinc trivalent chromate plating provides a bright silver/blue like finish, with the added benefit of ROHS Compliance. This chromate conversion coating is a type of coating used to passivate aluminum, zinc, cadmium, copper, silver, magnesium, and tin alloys. It is primarily used as a corrosion inhibitor, primer, decorative finish and it can retain electrical conductivity. Trivalent chromate is an iridescent conversion that can exhibit different hues. This is considered normal when applying iridescent conversions.

TRIZ - A Russian abbreviation for the "the theory of inventive problem solving." The term is pronounced "trees". It consists of 9 action steps and some 40 basic principles. (Further research this term)

TRUNCATION - In general terms truncation is some measure of the amount that was removed from a sharp V profile. A truncation at the major diameter of an external thread or the minor diameter of an internal thread is known as crest truncation. The truncation at the major diameter of an internal thread or the minor diameter of an external thread is known as root truncation. Truncation can be measured radially in which it is generally shown as a fraction of the theoretical thread height. It can also be measured axially in which case it is typically as a portion of the thread pitch.

TRUSS HEAD - Low rounded top surface with a flat bearing surface.

TRUSS HEAD - Has a rounded top with a flat bearing surface greater in area than a round head screw of the same nominal size. Weaker than pan or round heads but preferred in applications where minimal clearance exists above the head. Truss profile provides a trim finished appearance.

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 trout is run with new tools not previously approved.

TUBE UPSET - The forming of a hollow upset from a hollow preform.

TUMBLING - The process of cleaning or abrading parts in a rotating container, with or without cleaning or abrasive materials.

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.

TURBINE RIBS - The Turbine Ribs cut quickly into the wood, leaving a professional clean finish with maximum wood contact. The cup shaped countersinking provides increased holding power and reduced risk of splitting.

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

TURNING CENTER - AKA a lathe, a machining center that spins a workpiece in order to cut it.

TURRET PRESS - Automatic punch press indexing the material and selecting the intended tool out of the rotary tool holding device (turret) totally by computer control for piercing blanking and forming workpiece as programmed.

TWELVE POINT HEAD - A standard head form for externally wrenched screws designed for use in counterbored holes.

TWIN BLADE KNURLS - This set of knurls cuts fast to dramatically reduce friction and heat on the shank, while reducing load on the drill. They also provide better performance by removing debris faster than a standard fastener's knurl

TWO POINT TKO - A tool side kickout design that uses two intermediate rods connected by a bar. These are located between the TKO lever or rod in the heading slide and two spring loaded pins in the tooling. The pins are mounted on the vertical centerline of the tool bore and are attached to a plate. This design allows for the plate to be pulled back after the TKO stroke to get more die lubricant on the punch. This design also allows for shorter forming punches.

TYPE 1 / TYPE D - A thread cutting screw with a single flute for general use. Produces a fine standard machine screw thread for field replacement.

TYPE 17 - A thread cutting screw for wood with a coarse tapping screw thread and a special long sharp fluted to capture chips.

TYPE 23 / TYPE T - A thread cutting screw in the fine thread series offering maximum thread cutting area and excellent chip clearing with minimum tightening torques.

TYPE 25 / TYPE BT - A thread cutting screw similar to Type 23 point except with coarse Type B threads. For plastics and other soft materials with large chip clearing and cutting edges.

TYPE A - Sheet metal screws (tapping screws) with a sharp point, fewer threads per inch than Type AB screws, and deeper threads with better gripping power than Type AB screws. This thread forming screw is for use in thin metal .015 to .050 thick. Used with drilled, punched, or nested holes. Not recommended for new design.

TYPE AB - Sheet metal screws (tapping screws) with a sharp point and more threads than Type A screws, more like Type B sheet metal screws.

TYPE B / TYPE Z - Sheet metal screws (tapping screws) with a blunt point and more threads per inch than Type A screws. This thread forming screw is for use in heavier metal .050 to .200 thick. Larger root diameter with finer thread pitch for light and heavy sheet metal, non-ferrous castings, plastics, and other materials

TYPE BF - Type BF thread cutter has a blunt, tapered point with incomplete entering threads and multiple flutes for spaced threads. Used in plastics and fibre cement composites.

TYPE BG - Type BG has a slotted, blunt tapered thread for cutting point with incomplete entering threads.

TYPE BP - Type BP have a sharp, conical or pinched point applied to a Type B thread form screw. Screws are popular where there are misaligned holes.

TYPE C - A thread forming screw with either coarse or fine pitch machine screw threads and a blunt point. Eliminates chips and permits replacement with standard screw in the field. Higher driving torque required. Usable in heavy sheet metal and die castings.

TYPE D - Type D thread cutters have a blunt , tapered thread cutting point with incomplete entering threads and one flute for cutting.

TYPE F - A thread cutting screw with machine screw threads with blunt tapered point, having multi-cutting edges and chip cavities. For heavy gauge sheet metal, aluminum, zinc, and lead die castings, cast iron, brass and plastic.

TYPE FZ - A thread cutting screw with a tapping screw thread with blunt tapered point and multi-cutting edges and chip cavities. For Plastics, die castings, metal clad and resign impregnated plywood and asbestos.

TYPE U - A thread forming screw with high Helix thread for driving or hammering into sheet metal, castings. Or plastics for permanent quick assemblies.