McGuire Glossary of Fastener Terminology

B - 192 terms

B - When followed by a number (ex: B-90), hardness measured on the Rockwell Scale.

B - When referring to sheet metal screws, Type B indicates a blunt point with more threads per inch and smaller thread depth than a Type A sheet metal screw.

BACK FACE - In screw machine work, to face the back or cutoff end of a part after it has been cutoff while the work piece is held in the pickoff collet.

BACK WORK - General term applied to any operation done in the scree machine after the part has been cut off and is being held in the pick-off collet.

BACKING OFF - Loosening of a nut over time by spinning back up the thread.

BACKSIDE PROTRUSION - Protrusion of a fastener from the back side of the work piece. May apply to protrusion either before or after installing the fastener.

BACKWARD EXTRUSION - Forcing metal to flow on a direction opposite to the motion of a punch or die.

BACKWARD EXTRUSION - When metal is contained in a die or punch insert and forced to flow around a penetrating punch or pin. Typically applies to the forming of a hole in a workpiece.

BAKING - The process of heating fasteners for an extended period of time preferably within one hour after electroplating. This is done to reduce the risk of hydrogen embrittlement. Stress Relieving of parts that are over a hardness of HRc 30 that have had an electroplating operation.

BAKING - Fasteners to be electroplated that are RC38 or higher in hardness, should be further processed to relieve hydrogen embrittlement. This process should include baking at 395 deg. F for 8 hours or more within 4 hours of the plating process. If fasteners are over 40 RC, the baking should be for 24 hours minimum. The baking should be done before the chromate treatment. The fasteners are re-dipped in acid very briefly to reactivate the surface prior to chromate process.

BAKING OF CASE HARDENED PARTS - Electroplated fasteners which are case hardened should be baked for a minimum of four hours within the temperature range of 375-450 degrees F, no later than four hours after the plating process. This baking process does not guarantee that hydrogen embrittlement will not still be present after baking or that it will not occur at a later date while in service. Specialized testing or a substitute part may be required depending on the application.

BALANCE (GAGING) - The resultant non-movement on the display of an amplifier that occurs when one nozzle or a two-nozzle of a two-nozzle tool is closed toward the workpiece and the other nozzle equally compensates for the movement.

BALL LOCK TYPE DRIVING TOOL - This retention design uses a ball and spring tension method to secure sockets to an extension or adaptor. Tools can typically be removed by hand allowing for quick changes.

BANDING - Segregation of alloying elements in a metal, seen as parallel bands, in the direction of rolling.

BAR - A section hot rolled from a billet to a form, such as round, hexagonal, octagonal, square or rectangular, with sharp or rounded corners or edges, with a cross-sectional area of less than 16 sq in. (A solid section that is long in relation to its cross-sectional dimensions, having a completely symmetrical cross section and whose width or greatest distance between parallel faces is 3/8 inches or more.

BAR CODING - Machine readable alphabetic and/or numeric information used for identification of packaged parts.

BAR END - See End Loss.

BARREL - Long cylindrical portion of a fastener. Most used about a cylindrical portion of a standoff.

BARREL - Long cylindrical portion of a fastener. Most commonly used in reference to a cylindrical portion of a standoff. Also applied to the cylindrical portion of the type FE and PL locknuts. Sometimes applied to the cylindrical portion of Type B nuts

BARREL PLATING - A particular example of barrel processing by which electrodeposits are applied to articles in bulk: in contract to vat plating in which articles are individually suspended during the electrodeposition process.

BARREL PROCESSING - Mechanical, chemical or electrochemical treatment of articles in bulk in a rotating container. Examples: barrel burnishing, barrel polishing, barrel cleaning.

BARREL TUMBLING - Process in which parts to be deburred are put together with abrasive material into a barrel and rotated for prolonged periods for the purpose of burr removal.

BARRELING - Convexity of the surfaces of cylindrical or conical bodies, often produced unintentionally during upsetting or as a natural consequence during compression testing.

BARRIER PROTECTION - A method of fighting corrosion in which a layer of inert material (e.g. paint) is placed over the fastener to prevent rust.

BASE MATERIAL - The concrete, brick, or block material into which an anchor is placed.

BASE METAL - Opposite of noble metal. (Not to be confused with basis metal). Examples of base metals are aluminum, magnesium, zinc, cadmium, iron, etc.

BASIC SIZE - That size from which the limits of size are derived by the application of allowances and tolerance.

BASIC THREAD PROFILE - This is the theoretical profile of external and internal threads with no manufacturing tolerance applied.

BASIS MATERIAL - Material upon which coatings are deposited or formed (Not to be confused with base metal).

BATCH/BATCH-TYPE FURNACE - A furnace for heating materials where all loading and unloading is done through a single door or slot.

BDC OR B.D.C. - An abbreviation for Back Dead Center. This is when the heading slide is at the opposite end of the forming stroke, furthest from the face of the dies.

BEARING STRESS - The surface pressure acting on a joint face directly as a result of the force applied by the fastener.

BEARING SURFACE - The supporting or locating surface of a fastener (head or tail) with respect to the part which it fastens (mates). The loading of a fastener is usually through the bearing surface. Washers are commonly used to increase the bearing surface. A part of a fastener such as the washer face on a nut or under the head of a hex head cap screw that actually comes in contact with the part it fastens.

BEARING-TYPE JOINT - A bolted connection that assumes that shear forces are transmitted by the bolt bearing against the sides of the holes in the connected material. Often denote on drawings with an (X) (i.e. A-325-X) which excludes threads from the shear plane on (N) (i.e. A325-N) which includes threads in the shear plane.

BED - A stationary and rigid structure, typically constructed from metal, to which the bolster plate of metal stamping equipment is attached.

BED CUSHION - A plate or series of vertically moving plates mounted below the bolster plates of a press. The cushion helps regulate the metal flow by controlling the blank force.

BELL MOUTH - A slightly conical shape at the front of a tooling impression

BEND OR TWIST (DEFECT) - Distortion similar to warpage, but resulting from different causes; generally caused in the forging or trimming operations. When the distortion is along the length of the part, it is called (BEND), when across the width, it is called (TWIST).

BEND RADIUS - The radius of a bent pipe, tube, sheet, or cable measured from the inside curvature. It can also be defined as the minimum radius that an element can bend without kinking or sustaining damage.

BEND RELIEF - Clearance notch at an end of flange to allow bending without distorting or tearing adjacent material.

BEND TEST - A test commonly made by bending a cold sample of specified size through a specified circular angle. Bend tests provide an indication of the ductility of the sample.

BENDER - 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.

BENDING - Generally applied to forming. Creation of a formed feature by angular displacement of a sheet metal workpiece. A preliminary forging operation to give the piece approximately the correct shape for subsequent forming. Also note Drawing and Forming.

BENDING - Exactly as it sounds, bending is the process of twisting and flexing sheet metal or rod in a desired shape. Typically, pieces are bent around one axis into L-,U-, or V-shaped forms

BENDING FORCE - A force that acts to bend a component putting one side of the part in tension and the opposite side in compression. Bending forces have the same units as torque, but instead of twisting a part in-line with its longitudinal axis, bending forces can be applied in any orientation. Typically, these are described as prying or eccentric forces for fasteners.

BEST WIRE SIZE - The diameter of a wire that will contact the thread flank at the pith diameter. Best wire size can be calculated from thread pitch and flank angle using simple geometry.

BEVEL - A surface not at right angles to the rest of the piece. A small slant, usually describing a flat washer which is square and thicker on one side than the other. The slant of the beveled washer can offset a slanted surface, so that a bolt going into a beveled washer may be parallel to the ground.

BI-HEXAGON HEAD - A bolt or screw whose cross section of its head is in the shape of a 12 pointed star.

BILLET - A semi-finished, cogged, hot-rolled, or continuous-cast metal product of uniform section, usually rectangular with radiused corners. Billets are relatively larger than bars.

BINDING HEAD - Rounded top surface and slightly tapered sides. The bearing surface is flat, with annular undercut optional.

BITE - Amount of the die in contact with the workpiece throughout one entire forging reduction, e.g. heavy bite is three-quarter to full width of the die.

BLACK BOLTS & NUTS - The word black refers to the comparatively wider tolerances employed and not necessarily to the colour of the surface finish of the fastener.

BLACK NICKEL - Generally used as a matching finish without lacquer coating.

BLACK OXIDE - A "Conversion Coating" which means it is formed by a chemical reaction with the metal to form an integral surface, as opposed to an "Applied Coating" which bonds with the metal. An oil finish is applied as a rust inhibitor. No risk of hydrogen embrittlement. An attractive black finish. Salt Spray protection approaches 24 hours (ASTM-B-117) depending on he sealant used.

BLACK OXIDE OR BLACKENING - A conversion coating for ferrous mateerials, stainless steel , copper and copper-based alloys, zinc, powdered metals, and silver solder. It is used to add mild corrosion resistance, for appearance and to minmize light reflection.

BLACK PHOSPHATE - Standard finish on retaining rings, drywall and particle board screws. Color is dull black to a bright black appearance.

BLACK PHOSPHATE & OIL - Standard coating on black phosphate. Non-drying petroleum oil is 1100 mg per sq/ft minimum. Oil serves as a rust inhibitor and a lubricant. Some fasteners with this plating call out required salt-spray test. Common fasteners include frame bolts, spring nuts, floorboard screws and Grade GT locknuts.

BLACK ZINC - A shiny black appearance with fair rust resistance qualifies.

BLACKENING - Black finishing: Black Oxide

BLANK - Raw material or forging stock (also called a slug or multiple) from which a forging is made.

BLANK - (1) A specific length of stock after being sheared from the coil of wire. (2) A part while in the process of being formed. (3) A formed but not yet completed part. Example: Screw Blank

BLANK - A fastener in some intermediate stage of manufacture. The material has been cut to weight or length and is used to create forged parts, also known as forging stock.

BLANK - (1) Sheet metal stock from which a product is to be made. (2) Workpiece resulting from blanking operation. By stoking blanks, a fastener manufacturer can meet a variety of fastener orders.

BLANK - A stud that has been headed but has not yet been thread rolled. A defective condition in which a part is supposed to contain a thread, but does not contain a thread.

BLANK DIAMETER - Sometimes referred to as the before rolled diameter. The diameter of the pin portion of a headed stud onto which threads will be rolled.

BLANKING - Die cutting of the outside shape of a part.

BLANKING - Blanking involves cutting pieces out of a piece of sheet metal using a die. It creates clean components, or blanks, that can undergo further processing by the stamping press or other machinery.

BLAST CLEANING - A process for cleaning or finishing metal objects by use of an air jet or centrifugal wheel that propels abrasive particles (grit, sand, or shot) against the surfaces of the workpiece at high velocity.

BLASTING - A process in which particles are projected at high velocity against the work piece.

BLIND APPLICATION - Structure with access from only one side, requiring fasteners that can be fully installed from the exposed side.

BLIND FASTENER - A fastener that can be placed with access to only one side of the application.

BLIND HOLE - A hole which can only be accessed from one end.

BLIND INSERT - A straight, cylindrical insert pressed into a case with a mating counterbore. The insert does not go all the way through the case.

BLIND RIVET - A rivet designed for use where only one side of the work is accessible. A two-part fastener with a mandrel and a body (eyelet).

BLIND SIDE - The side of the joint, which cannot be accessed (e.g. the inside surface of a tubular or box section).

BLIND THREADED INSERT - Applies to an internal thread that does not go all the way through the product.

BLIND-SIDED HOLE - A type of hole that does not go completely through the material. Most screws are assembled into blind-threaded holes.

BLOCK - The forging operation in which metal is progressively formed to general desired shape and contour by means of an impression die (used when only one block operation is scheduled).

BLOCK AND FINISH - The forging operation in which the part to be forged is blocked and finished on one heat through the use of a die having both a block impression and a finish impression in the same die. This also covers the case where two tools mounted in the same machine are used, as in the case of aircraft pistons. Only one heat is involved for both operations.

BLOCK, FIRST AND SECOND - Blocking operation performed in a die having two blocking cavities in the same die; the part being forged is successively blocked in each impression all in one heat. As many as three blocker dies are sometimes needed for some forgings and up to three operations are sometimes required in each die.

BLOCK, FIRST, SECOND AND FINISH - The forging operation in which the part to be forged is passed in progressive order through three tools mounted in one forging machine; only one heat is involved for all three operations

BLOCKER IMPRESSION - The forging die impression which gives the forging its general shape, but omits any details that might restrict the metal flow; corners are well rounded. The primary purpose of the blocker is to enable the forming of shapes too complex to be finished after the preliminary operations; it also reduces die wear in the finishing impression.

BLOCKER-TYPE FORGING - A forging that approximates the general shape of the final part with relatively generous finish allowance and radii. Such forgings are sometimes specified to reduce die cost where only a small number of forgings are desired and the cost of machining each part to it final shape is exorbitant.

BLOOM - A semi-finished product of square, rectangular, or even round cross section, hot rolled, or forged. For steel, the width of a bloom is not more than twice the thickness, and the cross sectional area is usually not less than about 36 sq.in. No invariable rule prevails for distinguishing between blooms and billets; the terms are frequently used interchangeably.

BLOW - A particular forming operation or a give die or tool station.

BLOW UP - A term used in screw machine work to indicate a change in external dimensions which occurs in thin wall parts when they are tapped.

BLOW-OUT (Fastener) - A defective condition which occurs on cold formed or headed nuts at the piercing operation. Visible indication of blow out is missing material at the piercing punch exit side.

BLOW-OUT (MOUNTING HOLE) - Panel material sheared away during a hole punch operation causing the die side of the panel to exhibit a larger diameter hole than the punch side.

BLUE ANNEALING - Heating hot-rolled sheet in an open furnace to a temperature with the transformation range and then cooling in air to soften the metal. The formation of a bluish oxide on the surface is incidental.

BLUE POLYMER - Polymer is a barrier coating because it creates a seal around the fastener which resists corrosion and abrasion. A phosphate-zinc base is initially applied to the fastener, followed by the polymer which bonds to the sub-coating. Commonly used to coast and identify concrete screws.

BLUING - The formation of a very thin blue oxide film on steel either by heating in air or by immersion in concentrated oxidizing solutions.

BLUNT DIAMOND POINT - Dulled tip to reduce wood splitting; more difficult to work with comprised of 4 sides and ends in a point.

BLUNT START - The removal of the partial thread at the entering end of the thread.

BOARD HAMMER - A type of gravity drop hammer where wood boards attached to the ram are raised vertically be action on contrarotating rolls, then released. Energy for forging is obtained by the mass and velocity of the freely falling ram and the attached upper die. Also see Drop Hammer

BODY - The unthreaded portion of the shank of a threaded fastener. In blind fasteners, the portion of the rivet that expands into the parent material.

BODY - The portion of a breakstem blind rivet fastener that expands into the parent material.

BODY DIAMETER - The diameter of the body or smooth part of the bolt/screw above the threads. Also called shank diameter.

BODY LENGTH - See Shank Length

BODY-CENTERED CUBIC STRUCTURE (BCC) - A common crystal structure of steel. Refers to the arrangement of atoms within the metal. Atomically, it contains one lattice point in the center of the unite cell and eight corner points creating 2 full atoms per unit cell.

BOLSTER PLATE - A plate to which dies can be fastened; the assembly is secured to the top surface of a press bed. In press forging, such a plate may also be attached to the ram.

BOLT - An externally threaded fastener which accepts a nut in the application to produce the clamping load.

BOLT - A bolt is the term used for a threaded fastener, with a head, designed to be used in conjunction with a nut.

BOLT BLANK - A headed rod or bar intended for a subsequent threading operation.

BOLT CREEP/YIELD - Stress relaxation between the bolt and the washer is sometimes referred to as "bolt creep" or "bolt yield". This condition is the loss in bolt load due to elevated temperatures. The amount of loss depends on the bolt material, operating temperature, and the length of time at that temperature.

BOLT GRIP - For fasteners with a flat bearing surface head, the dimension from the bearing surface under the head to the end of the full diameter body, measured parallel to the axis of the fastener. For fasteners with a conical bearing surface head, the dimensions from the top of the head to the end of the full diameter, measured parallel to the axis of the fastener. Note that these definitions are similar to what some fastener standards use as the definitions for GRIP.

BOLT STOP - A spring loaded stop used in the trim station of Boltmakers that discharge trimmed bolts up through the heading side to the pointer. The stop keeps the trimmed bolts from falling back through the trim discharge tube and trim die.

BOND STRENGTH - The mechanical or chemical bonding capacity of an adhesive to both the insert and the base material.

BOROZING (BODDING) - A surface treatment procedure in which boron atoms are diffused into the workpiece by thermochemical treatment for purpose of increased hardness, wear and corrosion resistance.

BOSS - Protuberance on a plastic part designed to add strength and/or facilitate fastening or alignment.

BOSS - A relatively short protrusion or projection on the surface of a forging, often cylindrical in shape.

BOSS - A raised portion of material.

BOTTLING - The forward extrusion of a hollow part without a mandrel supporting the inside of the hole during extrusion.

BOTTOM DISCHARGE TRIM - A term used to describe the trim in the last station of a FORMAX., FORMAX PLUS, or large FORMAX PLUS machine.

BOTTOM FEED - Particular type of automatic installation tooling in which the part is automatically prsented onto the anvil.

BOUND BODY - (body-bound or fitted) A body which has a definite interference or extremely small clearance with mating hole.

BOW - The longitudinal curvature of the part of cutoff.

BOW DISTORTION - Out of flatness condition in sheet material commonly known as 'Oil Canning' in which, with the edges of the sheet restrained, the center of the sheet can be popped back and forth but cannot be flattened without specialized equipment.

BOW or CAMBER - The amount that a side of a fastener surface deviates from being straight.

BOX (NAIL) - A wire nail with a head; box nails have a smaller shank than common nails of the same size; often used for light general interior and exterior construction, carpentry, framing and box making.

BRAKE - A friction-operated mechanism used to arrest the movement of a press, feed, or other fabricated process or tool.

BRASS - An alloy composed primarily of two-thirds copper and secondarily one-third of zinc. Brass fasteners are non-magnetic and soft in comparison to steel. Brass has good strength and toughness, high electrical conductivity and an attractive lustrous finish. Brass is commonly used by the electrical and communications industries, builders hardware and some marine applications. Brass has good corrosion resistance, but not in salt water.

BRASS, ELECTROPLATED, LACQUERED - Brass electroplated which is then lacquered. Recommended for indoor decorative use only.

BREAK STEM - A fastener, which is installed by gripping and pulling the end of the mandrel/stem. As installation is completed, the end of the stem fractures at the braker groove and is discarded, leaving the head of the stem in the fastener body.

BREAKAWAY HEAD - The Breakaway head (also known as Breakoff or shear fastener) is a high-security fastener whose head breaks off during installation, during or immediately after the driving process, to leave only a smooth surface.

BREAKAWAY TORQUE - The torque necessary to put into reverse rotation a bolt that has not been tightened. Also known as Off-Torque" or "Removal Torque". Torque required to begin relative rotation between the part and mating thread absent an axial load. Subject to change with usage cycling. Considered the critical performance characteristic of a self-locking component.

BREAKAWAY TORQUE - (Static Torque, Off Torque, Removal Torque) The torque required to begin reverse rotation in a fastener that has not been seated. This will change with reuse - they are referred to as the "1st Off, 5th Off" Torque. This torque is due to the locking element only and is considered a critical performance characteristic of a locking component.

BREAKDOWN - (1) An initial rolling or drawing operation, or a series of such operations, for reducing an ingot or extruded shape to desired size before the finish reduction. (2) A preliminary press-forging operation.

BREAKER GROOVE - A weakened groove in the stem or pin of a fastener allowing breakage at a pre-determined load.

BREAKLOOSE TORQUE - The torque required to effect reverse rotation when a pre-stressed threaded assembly is loosened.

BREAKLOOSE TORQUE - The torque required to effect reverse rotation when a pre-stressed threaded assembly is loosened. The amount of torque required to overcome the axial load of a seated fastener (pre-load), relieving the tension, initiating movement in the off direction. A value unrelated to prevailing torque.

BREAKLOOSE TORQUE - The amount of torque required to put into reverse rotation a fastener that is in the seated, clamped por tightened position. The torque is due to clamp load and not related to prevailing torque. NYLOK

BREAKLOOSE TORQUE - The amount of torque required to put into reverse rotation a fastener that is in the seated, clamped or tightened position. The torque is due to clamp load and not related to prevailing torque.

BREAKLOOSE TORQUE - The torque required to begin reverse rotation in a fastener that has not been seated. This will change with reuse - they are referred to as the "1st Off, 5th Off" torque. This torque is due to the locking element only and is considered a critical performance characteristic of a locking component.

BREAKOUT - Fractured portion of the cross section of a cut edge of stock. A condition naturally occurring during shearing, blanking, punching and other cutting operations.

BRIGHT DIPPING - Brief immersion in a solution used to produce a bright surface on a metal.

BRIGHT FINISH - A finish with a uniform non-directional smooth surface of high specular reflectance.

BRIGHT NICKEL - Electroplated silver-color finish. Used for appliances, hardware, etc.

BRIGHT PLATING (ELECTROLYTIC) - A process that produces an electrodeposit having a high degree of specular reflectance in a as-plated condition.

BRIGHT PLATING RANGE - The range of current densities within an electroplating solution produces a bright deposit und a given set of operating conditions. Brightener: An addition agent in an electroplating solution that improves the brightness of an electrodeposit.

BRINELL HARDNESS - The hardness of a metal or part, as represented by the number obtained from the ratio between the load applied on and the spherical area of the impression made by a steel ball forced into the surface of the material tested. The Brinell Hardness Number (BHN) is determined by measuring the diameter of the impression using a low power microscope, then matching this diameter with the load on a standard table.

BRINELL HARDNESS SCALE - A hardness scale which measures the indentation resistance of a metal. Brinell hardness testing is performed by forcing a steel ball onto a material and measuring the dimensions of the indentation left by the ball. Brinelling refers to surface fatigue caused by repeated impact or overloading. It is common cause of roller bearing failures, and loss of preload in bolted joints when a hardened washer is not used. Engineers will use the Brinell hardness of materials in their calculations to avoid this mode of failure. Fretting corrosion can cause a similar-looking kind of damage and is called false brinelling since the mechanism is different. It was the first widely used and standardized hardness test in engineering.

BRINELL HARDNESS TEST - A method of determining the hardness of metallic materials by applying a known load to the surface of the materials through a hardened steel ball of known diameter. The diameter (or depth) of the resulting impression in the metal is measured. The Brinell hardness number is taken as the quotient of the applied load divided by the area of the surface impression, which is assumed to be spherical.

BRINELLING - Permanent surface deformation of one component by another, resulting from compressive loading.

BRISTOL DRIVE - Bristol drive (or Bristol Spline) with four or six splines, but is not necessarily tamper-resistant. The grooves in the wrench are cut by a square-cornered broach, giving a slight undercut to the outer corners of the driver. The main advantage to this drive system is that almost all of the turning force is applied at right angles to the fastener spline face, which reduces the possibility of stripping the fastener.

BRITISH STANDARD BRASS - A specialist thread form based upon the Whitworth thread and consisting of 26 threads per inch whatever the thread diameter.

BROACH - Similar to trimming but removes a very small amount of metal for a more accurately finished part.

BROACH - The action of pulling the mandrel though the Avdel speed fastener in order to place it.

BROACH - Term used to indicate the manufacture of a non-round hole. Also sometimes used as a noun to indicate the non-round hole. The square holes in type R retainers and the hex holes in type PL are produced by broaching.

BROACH LOAD - The force required to pull the mandrel through the Avdel speed fastener in order to place it.

BROACHING - The process of removing metal by pushing or pulling a cutting tool, called a broach, along the surface.

BROACHING - The act of cutting a shape in any object by using a mandrel of a similar shape. As applied to fasteners, the way a knurled shank "broaches" its way into the mounting hole.

BRONZE, ELECTROPLATED, LACQUERED - Has color similar to 80% copper, 20% zinc alloy. Electroplated and then lacquered. Recommended for indoor decorative use only.

BRUSH PLATING - As method of electrodeposition in which the electrolyte is applied with a pad or brush in contact with an electrode. The brush or pad is applied to the part to be processed which is given opposite polarity.

BSF - British Standard Fine. A thread form based upon the British Standard Whitworth form but with a finer thread (more threads per inch for a given diameter). This thread form was first introduced in 1908, the thread form is specified as BS 84:1956.

BSF BRITISH STANDARD FINE - A thread form based upon the British Standard Whitworth form but with a finer thread (more threads per inch for a given diameter). The thread form is specified in BS 84:1956.

BSW BRITISH STANDARD WHITWORTH - A thread form developed by Sir Joseph Whitworth in 1841. The thread form has rounded roots and crests, the thread form is specified as BS 84: 1956. This thread from was superceded by the United thread in 1948 and then the metric thread form.

BUBBLE - The largest diameter portion of the locking feature on type LK nuts.

BUCK-TAIL - The end of a solid tubular rivet, opposite the head, which is upset, or bucked (deformed) to expand the shaft diameter 1.5 times holding the rivet in place.

BUCKING BAR - A uniquely shaped weight used as an impact reaction mass, at the end of a fastener opposite to the applied load, in forming an upset button on a rivet

BUCKLING - Uncontrolled bending of stock during upsetting. Also encountered on tooling components without proper guide or exceeding the unsupported length.

BUCKLING - The tendency of a compression spring to bow or to deflect laterally, when loaded

BUCKLING (Spring Term) - A bulge, bend, kink, or other wavy condition of the workpiece caused by compressive stresses. The bowing or lateral deflection of compression springs when compressed, related to the slenderness ratio (L/D)

BUFFER - A substance that, when contained in a solution counteracts changes in pH. Each buffer has a characteristic range of pH over which it is effective.

BUFFING (MOPPING) - The smoothing of a surface by means of a rotating flexible wheel to the surface of which is fine, abrasive particles are applied in liquid suspension, paste or grease stick form.

BUGLE HEAD - Similar to countersunk head with a smooth progression from the shank to the angle of the head, similar to the bell of a bugle. Bugle heads that allows the screw to depress the wood surface without breaking it. Used on Deck Screws and Drywall Screws.

BULB - The largest diameter portion above the flange ontype SSC or SSA snaptop standoffs. Also sometimes used to mean the same as bubble on LK nuts.

BULB DIAMETER - The diameter of the bulb. When an insert is used near max grip the bulb diameter will be smaller than when the insert is used near min grip. Thick wall parts have historically been designed to provide a bulb diameter of 125% of shank diameter at max grip and 135% of shank diameter at min brip

BULBING - The physical action of the fastener body swelling (expanding radially) against the rear face of the joint when placed. Generally found in break stem fasteners and threaded inserts.

BULL NOSE - A style of bit where the tip of the bit is a larger diameter than the hex shank body.

BULLNOSE - To make a portion of a tool or die case that is not contained by the tool holder or die block larger in diameter. This gives improved support to the inserted assembly.

BUMP THREAD - A modified thread profile patented and trademark of Bosco Tool Inc. The thread form has a small projection at the pitch diameter that eliminates the clearance from the thread assembly on both flanks. By doing this it is claimed that resistance to vibration loosening is significantly improved.

BURN MARK - Heat discoloration created in the contact area of a welding electrode.

BURNING - Permanently damaging a metal or alloy by heating so as to cause either incipient melting or intergranular oxidation.

BURNISH - A forming operation that produces a smooth, polished surface by rubbing. Usually forcing a slightly larger diameter punch or pin through a hole in the part or forcing a part through a slightly smaller die orifice. The punch or die has a smooth surface to produce a polished finish.

BURNISHING - The process of producing a smooth surface by rubbing or rolling a tool against the surface.

BURNISHING - The smoothing of surfaces by ribbing under pressure, essentially without removal of the surface layer.

BURNT DEPOSIT - A rough unsatisfactory deposit produced by an excessive current density.

BURR - A small amount of material extended out from the edge of a hole, shoulder, etc. as the result of a machining operation.

BURR - Raised, sharp edge inherent in cutting operations such as shearing, blanking, punching and drilling.

BURR - A thin ridge or roughness left on forgings by cutting operation such as slitting, shearing, trimming, blanking or sawing.

BURR DIRECTION - Side of the stock on which burrs appear.

BURR FREE - In the context of a self-locking components, this reference applies to the milled area of strip and pellet installation areas.

BURR HEIGHT - Height of which burr is raised beyond the surface of the material.

BURR ROLLOVER - Condition of burr displacement resulting from mechanical deburring operation.

BURR-FREE - Edge without sharp protrusions

BURST - A seam or other wire defect which opens when the material is upset.

BUS BAR - A rigid conductor for carrying current, for example, to the anode and cathode bars.

BUSTER (PREBLOCKING IMPRESSION) - A type of die impression sometimes used to combine preliminary forging operations such as edging and fullering with the blocking operation to eliminated blows.

BUSTER (ROUGHER) - An impression employed in a die when considerable metal movement is required and which precedes a blocker cavity and a finisher cavity. Also known as breakdown/pancake, scalebreak, cheese.

BUTTON HEAD - A head with a low, rounded top surface and a flat bearing surface. Notably, a Button Head Socket Head Cap Screws.

BUTTON UPSET - Typically refers to the head preform of a bolt blank prior to the trimming operation.

BUTTRESS THREAD - A thread with an asymmetrical ridge that has one straight and one angled flank.