www.boltscience.com 10.04.13

7/27/2019 Www.boltscience.com 10.04.13

1/55

www.boltscience.com 10.04.13

http://www.boltscience.com/pages/glossary.htm

Glossary

Terminology related to nuts and bolts

Presented below is a glossary of terminology on topics related to nuts and bolts, threaded fasteners and

tightening techniques. If you have any questions about any of the content or you think we've missed somethingwhy not send us an Email on the topic.

A| B |C| D | E| F | G | H | I | J | K| L |M |N | O | P | Q | R| S | T | U | V |W | X |Y| Z

We have a web site dedicated to training, have a look at www.bolting.info - for additionalinformation on bolting technology.ACORN NUT

A nut (so-called because of its shape) that has a domed top sothat it prevents contact with the external thread.

AEROTIGHT NUTA torque prevailing nut of all metalconstruction. The nut is slotted in two

places which, after the nut has beentapped, are bent slightly inwards anddownwards. When the nut is screwed ontothe bolt thread the two slotted parts are forced back to theiroriginal position. Their stiffness causes the nut threads to bind ontothe bolt threads and thus provides a prevailing torque.Aerotight is a registered trade mark of The Premier Screw andRepitition Co. Ltd of Woodgate, Leicester, United Kingdom, LE35GJ.

ANTI-FRICTION COATING
http://www.boltscience.com/http://www.boltscience.com/pages/glossary.htmmailto:[email protected]://www.boltscience.com/pages/glossary.htm#ahttp://www.boltscience.com/pages/glossary.htm#ahttp://www.boltscience.com/pages/glossary.htm#bhttp://www.boltscience.com/pages/glossary.htm#chttp://www.boltscience.com/pages/glossary.htm#chttp://www.boltscience.com/pages/glossary.htm#chttp://www.boltscience.com/pages/glossary.htm#dhttp://www.boltscience.com/pages/glossary.htm#ehttp://www.boltscience.com/pages/glossary.htm#ehttp://www.boltscience.com/pages/glossary.htm#fhttp://www.boltscience.com/pages/glossary.htm#ghttp://www.boltscience.com/pages/glossary.htm#hhttp://www.boltscience.com/pages/glossary.htm#ihttp://www.boltscience.com/pages/glossary.htm#jhttp://www.boltscience.com/pages/glossary.htm#khttp://www.boltscience.com/pages/glossary.htm#lhttp://www.boltscience.com/pages/glossary.htm#mhttp://www.boltscience.com/pages/glossary.htm#mhttp://www.boltscience.com/pages/glossary.htm#nhttp://www.boltscience.com/pages/glossary.htm#nhttp://www.boltscience.com/pages/glossary.htm#ohttp://www.boltscience.com/pages/glossary.htm#phttp://www.boltscience.com/pages/glossary.htm#qhttp://www.boltscience.com/pages/glossary.htm#rhttp://www.boltscience.com/pages/glossary.htm#shttp://www.boltscience.com/pages/glossary.htm#thttp://www.boltscience.com/pages/glossary.htm#uhttp://www.boltscience.com/pages/glossary.htm#vhttp://www.boltscience.com/pages/glossary.htm#whttp://www.boltscience.com/pages/glossary.htm#whttp://www.boltscience.com/pages/glossary.htm#whttp://www.boltscience.com/pages/glossary.htm#whttp://www.boltscience.com/pages/glossary.htm#whttp://www.boltscience.com/pages/glossary.htm#whttp://www.boltscience.com/pages/glossary.htm#whttp://www.bolting.info/http://www.boltscience.com/http://www.boltscience.com/pages/glossary.htmmailto:[email protected]://www.boltscience.com/pages/glossary.htm#ahttp://www.boltscience.com/pages/glossary.htm#bhttp://www.boltscience.com/pages/glossary.htm#chttp://www.boltscience.com/pages/glossary.htm#dhttp://www.boltscience.com/pages/glossary.htm#ehttp://www.boltscience.com/pages/glossary.htm#fhttp://www.boltscience.com/pages/glossary.htm#ghttp://www.boltscience.com/pages/glossary.htm#hhttp://www.boltscience.com/pages/glossary.htm#ihttp://www.boltscience.com/pages/glossary.htm#jhttp://www.boltscience.com/pages/glossary.htm#khttp://www.boltscience.com/pages/glossary.htm#lhttp://www.boltscience.com/pages/glossary.htm#mhttp://www.boltscience.com/pages/glossary.htm#nhttp://www.boltscience.com/pages/glossary.htm#ohttp://www.boltscience.com/pages/glossary.htm#phttp://www.boltscience.com/pages/glossary.htm#qhttp://www.boltscience.com/pages/glossary.htm#rhttp://www.boltscience.com/pages/glossary.htm#shttp://www.boltscience.com/pages/glossary.htm#thttp://www.boltscience.com/pages/glossary.htm#uhttp://www.boltscience.com/pages/glossary.htm#vhttp://www.boltscience.com/pages/glossary.htm#whttp://www.boltscience.com/pages/glossary.htm#whttp://www.boltscience.com/pages/glossary.htm#whttp://www.boltscience.com/pages/glossary.htm#whttp://www.bolting.info/


2/55

AF coatings are dry lubricants consisting of suspensions of solid lubricants, such asgraphite, PTFE or molydbenum disulphide of small particle size in a binder. Such coatingscan be applied to fastener threads to replace metallic coatings such as zinc and cadmiumand offer maintenance free permanent lubrication. By careful selection of the lubricants,

AF coatings can be designed to meet specific applications. The coatings are permanentlybonded to the metal surface and provide a lubricating film preventing direct metal tometal contact.

ANTI-SEIZE COMPOUNDAn anti-seize compound is used on the threads of fasteners in some applications. Thepurpose of the compound depends upon the application. It can prevent galling of matingsurfaces - such compounds are frequently used with stainless steel fasteners to preventthis effect from occurring. In some applications it is used to improve corrosion resistanceto allow the parts to be subsequently dis-assembled Thirdly, it can provide a barrier towater penetration since the threads are sealed by use of the compound.

AUTOLOK NUT

A torque prevailing nut of an all metal construction. Covered by UK patent 1180842 thenut is marketed by GKN Screws and Fasteners Limited.ALLOWANCE

An intentional clearance between internal or external thread and the design form of thethread when the thread form is on it's maximum metal condition. Not all classes of fithave an allowance. For metric threads the allowance is called the fundamental deviation.

ANAEROBIC ADHESIVEAn adhesive which hardens in the absence of air, such adhesives are often used as athread locking medium.

ANGLE CONTROLLED TIGHTENINGA tightening procedure in which a fastener is first tightened by a pre-selected torque

(called the snug torque) so that the clamped surfaces are pulled together, and then isfurther tightened by giving the nut an additional measured rotation. Frequently bolts aretightened beyond their yield point by this method in order to ensure that a precise preloadis achieved. Bolts of short length can be elongated too much by this method and the boltmaterial must be sufficiently ductile to cater for the plastic deformation involved. Becauseof the bolt being tightened beyond yield, its re-use is limited.

BASIC THREAD PROFILEThis is the theoretical profile of external and internal threads with no manufacturingtolerance applied.


3/55

BEARING STRESSThe surface pressure acting on a joint face directly as a result of the force applied by afastener.

BIHEXAGON HEAD

A bolt or screw whose cross section of its head is in the shape of a 12 pointed star.BLACK BOLTS AND NUTSThe word black refers to the comparatively wider tolerances employed and not necessarilyto the colour of the surface finish of the fastener.

BOLTA bolt is the term used for a threaded fastener, with a head, designed to be used inconjunction with a nut.

BREAKAWAY TORQUEThe torque necessary to put into reverse rotation a bolt that has not been tightened.

BREAKLOOSE TORQUEThe torque required to effect reverse rotation when a pre-stressed threaded assembly is

loosened.BRITISH STANDARD BRASSA specialist thread form based upon the Whitworth thread and consisting of 26 threadsper inch whatever the thread diameter.

BSFBritish Standard Fine. A thread form based upon the British Standard Whitworth form butwith a finer thread (more threads per inch for a given diameter). This thread form was firstintroduced in 1908, the thread form is specified in BS 84: 1956.

BSWBritish Standard Whitworth. A thread form developed by Sir Joseph Whitworth in 1841. Thethread form has rounded roots and crests, the thread form is specified in BS 84: 1956.

This thread form was superceded by the Unified thread in 1948 and then the metricthread form.

BUMP THREADA modified thread profile patented and trade mark of the Bosco Tool Inc. The thread formhas a small projection at the pitch diameter that eliminates the clearance from the threadassembly on both flanks. By doing this it is claimed that resistance to vibration looseningis significantly improved.

CADMIUM ELECTROPLATINGCoating of threaded fasteners with cadmium can provide the parts with excellent
http://www.boltscience.com/index.htmhttp://www.boltscience.com/pages/aboutus.htmhttp://www.boltscience.com/pages/copyright.htmhttp://www.boltscience.com/index.htmhttp://www.boltscience.com/pages/copyright.htmhttp://www.boltscience.com/pages/contact.htmhttp://www.gizmology.net/nutsbolts.htmhttp://www.gizmology.net/nutsbolts.htmhttp://www.boltscience.com/index.htmhttp://www.boltscience.com/pages/aboutus.htmhttp://www.boltscience.com/pages/software.htmhttp://www.boltscience.com/pages/services.htmhttp://www.boltscience.com/pages/training.htmhttp://www.boltscience.com/pages/download.htmhttp://www.boltscience.com/pages/pricing.htmhttp://www.boltscience.com/pages/info.htmhttp://www.boltscience.com/pages/copyright.htmhttp://www.boltscience.com/index.htmhttp://www.boltscience.com/pages/contact.htmhttp://www.gizmology.net/nutsbolts.htm


4/55

corrosion resistance. The appearance of the coating is bright silver or yellow ifsubsequently passivated. The friction values associated with this coating are alsocomparatively low. A chromate conversion coating is frequently applied to the surface toimprove corrosion resistance. Cadmium is not now frequently used because of the

environmental and worker health problems associated with the coating process andshould not be used in applications above 250C or when contact with food is possible.CLAMPING FORCE

The compressive force which a fastener exerts on the joint.CLASS OF FIT

The Class of Fit is a measure of the degree of fit between mating internal and externalthreads. Three main Classes of Fit are defined for metric screw threads :FINE: This has a tolerance class of5H for internal threads and 4h for external threads.MEDIUM: This has a tolerance class of 6H for internal threads and 6g for external threads.COARSE: This has a tolerance class of 7H for internal threads and 8g for external threads.For Unified threads, a similar designation as for metric threads is used. The thread classes

used are 1A, 2A and 3A for external threads and 1B, 2B and 3B forinternal threads.CLEVELOC NUT

A torque prevailing nut of all metal construction. The collar of thenut is elliptical in cross section and it is this that provides theflexible locking element. The nut is pre-lubricated to reduce thetorque needed when tightening and to minimise galling.

COEFFICIENT OF FRICTIONA dimensionless number representing the ratio of the friction forceto normal force. Typically for threaded connections it is between0.10 to 0,18 but can vary significantly depending upon the

materials used and whether a lubricant has been used. In relationto threaded fasteners, the coefficent of friction can be further sub-divided into the coefficient of friction between the threads and the coefficient of frictionunder the nut face. There is in general a difference in values between the two coefficientsdue to typically the contact surfaces being different. For example, a zinc plated nut on azinc plated bolt, the thread coefficent of friction would be due to zinc plating contactingzinc plating. The nut face coefficient of friction would be due to zinc plating contacting the

joint surface finish.COMMINGLING
http://www.nutsandbolts.co.uk/http://www.nutsandbolts.co.uk/http://www.nutsandbolts.co.uk/http://www.nutsandbolts.co.uk/http://www.nutsandbolts.co.uk/http://www.nutsandbolts.co.uk/http://www.spiralock.com/http://www.nutsandbolts.co.uk/http://www.spiralock.com/


5/55

A term used to describe the undesirable practice of mixing fasteners from differentbatches that are the same size and grade in the same container.

CONELOC NUTThe Coneloc is an all metal prevailing torque type self-locking

nut. The locking action is achieved by localised precisiondeformation of the thread in the cone section on top of thenut. When the nut is tightened onto the bolt, the thread isgripped on the flanks providing the locking action. Coneloc is atrade mark ofNUTS BOLTS Limited

CONE PROOF LOADThis is an axial applied force applied to a nut when it is seatedon a cone shaped washer which has an included angle of 120degrees. Failure in this test is usually due to the nut splitting. The intention of the test isto introduce a nut dilation operation which will assess the potential detrimental effects ofsurface discontinuities. This type of test is sometimes applied to nuts which are intended

for high temperature service.CREEPCreep is deformation with time when a part is subjected to constant stress. Metals creepcan occur at elevated temperature however with gasket materials it can occur at normalambient temperatures. Creep resistance is an important property of gasket materials.Gasket materials are designed to flow under stress to fill any irregularities in the flangesurface. The amount of creep sustained tends to increase with temperature. . Howeveronce the tightening is completed it is important that no further flow occurs since suchdeformation will lead to a reduction in bolt extension and subsequently the stress actingon the gasket. If this stress is reduced to below a certain minimum, which depends uponthe type and construction of the gasket and the operating temperature, a high rate of

leakage can be anticipated to occur.

DECOMPRESSION POINTThe point at which there is zero pressure at the joint interface as a result of forces appliedto the joint. If the applied force is increased beyond the decompression point, a gap willform at the interface. Analytically, a criteria of joint failure is often taken as when theapplied force on the joint reaches the decompression point. This is because forces actingon the bolt(s) can dramatically increase at this point. Loading beyond this point can alsoresult in fretting at the interface that will lead to bolt tension loss that will subsequently


6/55

lower the decompression point. This process can continue until bolt failure does occur.The failure can be by fatigue or other mechanism but the underlying cause was loading ofthe joint beyond the decompression point. It is for this reason that it is frequently taken asa failure criteria in analysis work.

DACROMETA high performance surface coating that can be applied to fasteners. The coating consistsof passivated zinc flakes that are stoved onto the metal surface. The coating can becoloured and eliminates the risk of hydrogen embrittlement associated with electroplatedmetal. DACROMET is a registered trademark of Metal Coatings International, Inc. ofChardon Ohio

DESIGN FORM OF THREADThe design form of an internal or external thread is the thread form in it's maximum metalcondition. It is the same as the basic thread profile except that the thread roots arerounded. If either the internal or external thread form exceeds the design form of thethread profile then a potential interference exists.

DIRECT TENSION INDICATORSDirect Tension Indicators (DTI's) is a term sometimes used to describe load indicatingwashers. Projections on the face of the washer (usually on the face abuting the bolt heador nut) that deform under loading as the bolt is tensioned. An indication of the tension inthe bolt can be made by measuring the gap between the washer face and the nut or bolthead. The smaller the gap - the greater the tension in the bolt. Commonly used in civilrather than mechanical engineering applications.

DYNAMIC FRICTIONResistance to relative movement of two bodies that are already in motion.

EFFECTIVE DIAMETERThis is the diameter of an imaginary cylinder coaxial with the thread, which has equal

metal and space widths. It is often referred to as pitch diameter. Sometimes referred to asthe simple effective diameter to differentiate from the virtual effective diameter.EFFECTIVE NUT DIAMETER

Twice the effective nut radius.EFFECTIVE NUT RADIUS

The radius from the centre of the nut to the point where the contact forces, generatedwhen the nut is turned, can be considered to act.

ELECTROLESS NICKELA relatively thin, hard coating that can be applied to threads and deposited uniformly.


7/55

Bright metallic in appearance this coating has excellent resistance to wear and corrosion.EMBEDMENT

Localized plastic deformation which occurs in the vicinity of clamped fasteners or in thefastener threads. . Embedding is local plastic deformations that occur under the nut face,in the joint faces and in the threads as a result of plastic flattening of the surfaceroughness. This occurs even when the loading is below the yield point of the bolt orlimiting surface pressure of the joint material and is the result of the real area of contactbetween surfaces being less than the apparent area.

ENVIRONMENTALLY ASSISTED CRACKING (EAC)A process that can occur with the use of high strength steel fasteners in which crackinitiation and growth occurs in the fastener at a comparatively low stress level as a resultof interactions that occur with the environment. Hydrogen is suspected of causing EAC inhigh strength steel fasteners, the hydrogen being produced as a result of chemicalreactions (galvanic corrosion in a moist environment) or being present from a platingprocess that may have been applied to the fastener.

EXTERNAL FORCE OR LOADForces exerted on a fastener as a result of an applied loading to the joint.EXTERNAL THREAD

A screw thread which is formed on an external cylinder, such as on bolts, screws, studsetc.

FLOATING TYPE FLANGE JOINTA conventional flanged joint in which a gasket is compressed by bolts - the gasket is notrigidly located. Calculation methods such as the ASME code in the USA and the EN1591code in Europe.

FLUORO-CARBON THREAD COATINGA low friction coating applied to threads. This type of coating is frequently used to prevent

thread fouling when an assembly containing threaded fasteners is painted. Unless maskedin some way before painting, electro deposited primers can cover the threads. If thisoccurs assembly difficulties can result unless the expensive chore of cleaning the threadsis completed. A fluoro-carbon thread coating eliminates the need for masking or cleaningsince paint will not adhere to the coating. This type of coating can also prevent problemscaused by weld splatter obstructing the threads of weld nuts during their placement. Suchcoatings also have the property of reducing the torque-tension scatter during tightening.

FRICTIONMechanical resistance to the relative movement of two surfaces. There are two main
http://www.usi.edu/science/engrtech/COURSWRK/met371/UN_thrds.htmhttp://www.usi.edu/science/engrtech/COURSWRK/met371/UN_thrds.htm


8/55

types of friction; STATIC FRICTION and DYNAMIC FRICTION. Typically static friction isgreater than dynamic friction.

FRICTION STABILIZERSCoating materials used on fasteners with the intention of reducing the scatter in thethread and bearing surface friction coefficients.

FUNDAMENTAL DEVIATIONAn intentional clearance between internal or external thread and the design form of thethread when the thread form is on it's maximum metal condition. For metric threads thefundamental deviation are designated by letters, capitals for internal threads and smallletters for external threads. Some tolerance classes have a fundamental deviation of zero.For imperial threads the fundamental deviation is called the allowance.

FUNDAMENTAL TRIANGLE HEIGHTThe fundamental triangle height is normally designated with the letter H. This is theheight of the thread when the profile is extended to a sharp vee form. For 60 degreethread forms such as metric and Unified thread series, H equals 0.866025 times the

thread pitch.GALLINGA severe form of adhesive wear which occurs during sliding contact of one surface relativeto another. Clumps of one part stick to the mating part and break away from the surface.(Can frequently occur when both the nut and bolt are made from stainless or high alloysteels, titanium or zinc coated fasteners.)

GRIP LENGTHTotal distance between the underside of the nut to the bearing face of the bolt head;includes washer, gasket thickness etc.

HARD JOINTA joint in which the plates and material between the nut and bolt bearing surfaces have a

high stiffness when subjected to compression by the bolt load. A joint is usually defined ashard if the bolt is tightened to its full torque and it rotates through an angle of 30 degreesor less after it has been tightened to its snug condition.

HARDENED WASHERSThe force under the head of a bolt or nut can exceed, at high preloads, the compressiveyield strength of the clamped material. If this occurs excessive embedding anddeformation can result in bolt preload loss. To overcome this hardened washers under thebolt head can be used to distribute the force over a wider area into the clamped material.A more modern alternative is to use a flange headed nuts and bolts.
http://www.boltscience.com/pages/glossary.htm#LOCKNUThttp://www.boltscience.com/pages/glossary.htm#YIELDCONTROLhttp://www.boltscience.com/pages/glossary.htm#LOCKNUThttp://www.boltscience.com/pages/glossary.htm#YIELDCONTROL


9/55

HEAT TIGHTENINGHeat tightening utilises the thermal expansion characteristics of the bolt. The bolt isheated and expands: the nut is indexed (using the angle of turn method) and the systemallowed to cool. As the bolt attempts to contract it is constrained longitudinally by theclamped material and a preload results. Methods of heating include direct flame, sheathedheating coil and carbon resistance elements. The process is slow, especially if the strain inthe bolt is to be measured, since the system must return to ambient temperature for eachmeasurement. This is not a widely used method and is generally used only on very largebolts.

HELICAL SPRING WASHERA split type of spring washer whose purpose is to prevent self loosening of the nut or thebolt. The idea or principle behind the helical spring washer is for one end of the tang ofthe washer to indent into the fastener (the nut or bolt head) and the other into the jointsurface so that any loosening rotation is prevented. Junker in his paper in 1969 on thecause of self-loosening of fasteners (reference:Junker, G., New criteria for self-loosening of

fasteners under vibration. SAE Paper 690055, 1969) concluded that this type of lockwasher has no ability to lock. This type of washer is sometimes called a spring lock washeror sometimes a standard lock washer.

HIGH STRENGTH FRICTION GRIP BOLTSSometimes abbreviated to HSFG bolts. Bolts which are of high tensile strength used inconjunction with high strength nuts and hardened steel washers in structural steelwork.

The bolts are tightened to a specified minimum shank tension so that transverse loads aretransferred across the joint by friction between the plates rather than by shear across thebolt shank.

HOLD AND DRIVE BOLTS

Special bolts that have a tang at the threaded end of the shank. This tang is gripped bythe tightening tool during assembly so that the reaction torque is absorbed whilst the nutis tightened from the same side. Such bolts allow what used to have to be done by twomen to become a one-man task.

HOT BOLTINGThis term is used for the completion of maintenance work on a bolted joint when the jointis under loading. This can involve the replacement of individual bolts. There are risks bothto the joint itself and to health and safety associated with this technique.

HYDRAULIC TENSIONER


10/55

A hydraulic tool used to tighten a fastener by stretching it rather than applying a largetorque to the nut. After the fastener has been stretched, the nut is run down the thread tosnug up with the joint, the hydraulically applied load is then removed resulting in tensionbeing induced into the fastener.

HYDROGEN EMBRITTLEMENTSteel fasteners exposed to hydrogen can fail prematurely at a stress level well below thematerials yield strength. Hydrogen embrittlement occurs in fasteners usually as a result ofthe part being exposed to hydrogen at some time during its manufacturing process but itcan also occur through in-service corrosion. Electroplating is generally considered to be amajor cause of hydrogen absorption in steel fasteners due to the release of hydrogenduring this process. Higher strength steels are more susceptible to hydrogenembrittlement than lower strength steels, however it is considered that there is no lowerstrength limit. As a rule of thumb, steels below Rockwell C 35 are considered to be far lesssusceptible. Tests such as the incremental load hydrogen embrittlement test can becompleted to assess if hydrogen embrittlement is present in a batch of fasteners.

IMPACT WRENCHA wrench, usually powered by electricity or air, in which repeated blows from littlehammers are used to generate torque to tighten fasteners. The torque applied to thefastener depends upon the time and the air pressure applied to the tool (for pneumaticwrenches). The torque applied by an impact wrench to a fastener is influenced by the jointstiffness.

INSTANTANEOUS CENTRE OF ROTATIONThe point in space that an eccentrically shear loaded joint rotates about. The deformationand the load sustained by an individual bolt in a bolt group is dependent upon thedistance that the bolt is from the instantaneous centre. The direction that the individualbolt force acts is perpendicular to a line joining that bolt to the instantaneous centre.

INTEGRAL FASTENERA term used to describe types of fasteners which are highly resistant to vibrationloosening and/or removal. Some types have special thread forms.

INTERNAL THREADA screw thread which is formed in holes, such as in nuts.

JAM NUTSSee LOCKNUT

JOINT CONTROL TIGHTENINGSeeYIELD CONTROLLED TIGHTENING


11/55

JOST EFFECTThe name given to the reduction in the frictional resistance that occurs in a directiondifferent to that inwhich slip is occurring. This effect is used in many applications includingthe removal of corks from bottles. If the cork is first rotated the force needed to pull thecork from the bottle is significantly reduced. It is also the fundamental reason whythreaded fasteners experience self-loosening. Frictional resistance is first overcome in thetransverse direction by slip occurring on the joint resulting in the frictional resistance inthe circumferential direction reducing to a small value. The torque acting on the fastenerin the loosening direction (as a result of its preload) that when coupled with the Jost Effectresults in self-loosening occurring.

The term is named after the Institute that completed research into this effect, the Jost Institute of

Tribotechnology at the University of Central Lancashire in the UK.

K FACTOR

The factor in the torque tightening equation: T=KDF where T is the fastener tighteningtorque in Newton metres, D is the fastener diameter in metres, F is the fasteners preloadin Newtons and K is a factor whose value is often taken as 0.2. The formula gives theapproximate tightening torque for standard fasteners used under normal conditions. The Kfactor is also known as the nut factor and the torque coefficient.

KEPSA pre-assembled nut and washer assembly (the washer is attached to the nut so that itwon't fall off)- a trademark of ITW Shakeproof. The origin of the word came fromShaKEProof. The s on the end being acquired due to them being purchased in quantitiesusually greater than one.

LEFTHAND THREAD

A screw thread that is screwed in by rotating counterclockwise.LENGTH OF ENGAGEMENT

The axial distance over which an external thread is in contact with an internal thread.LOCK NUT

There are two common usage's of this term:1. A nut which provides extra resistance to vibration loosening by either providing someform of prevailing torque, or, in free spinning nuts, by deforming and/or biting into matingparts when fully tightened.2. The term is sometimes used for thin (or jam) nuts used to lock a thicker nut. When used
mailto:[email protected]://www.colinusher.info/Livesteam/mewdata.htmlhttp://www.gizmology.net/index.htmhttp://www.gizmology.net/index.htmhttp://en.wikipedia.org/wiki/Screwhttp://en.wikipedia.org/wiki/Screw#mw-navigationhttp://en.wikipedia.org/wiki/Screw#p-searchhttp://en.wikipedia.org/wiki/Screw_(disambiguation)mailto:[email protected]://www.coburnmyers.com/html/technical_dimensional_specifications.asphttp://www.colinusher.info/Livesteam/mewdata.htmlhttp://www.gizmology.net/index.htmhttp://en.wikipedia.org/wiki/Screwhttp://en.wikipedia.org/wiki/Screw#mw-navigationhttp://en.wikipedia.org/wiki/Screw#p-searchhttp://en.wikipedia.org/wiki/Screw_(simple_machine)http://en.wikipedia.org/wiki/Screw_(disambiguation)


12/55

in this way the thin nut should be adjacent to the joint surface and tightened against thethick nut. If placed on top of the thick nut the thin nut would sustain loads it was notdesigned to sustain.

MAJOR DIAMETERThis is the diameter of an imaginary cylinder parallel with the crests of the thread; inother words it is the distance from crest to crest for an external thread, or root to root foran internal thread.

MEANSHIFTThe difference in tightening torque values produced by the same tightening tool on hardand soft joints. A hard joint typically gives a higher torque value than a soft joint.Generally speaking, the lower the meanshift of a tightening tool, the better it will be inachieving a specified torque value irrespective of the joint condition.

METAL TO METAL CONTACT FLANGE JOINTA flanged joint in which a gasket is compressed by bolts - the gasket being located in arecess within the joint so that it is compressed by the bolt loads until metal to metal

contact occurs. Unlike the FLOATING TYPE FLANGE JOINT, for metal to metal type jointsthere are no standardised gasket factor definitions, test procedures, nor generallyacknowledged calculation procedures available.

MINOR DIAMETERThis is the diameter of an imaginary cylinder which just touches the roots of an externalthread, or the crests of an internal thread.

MODEL ENGINEERS THREAD (M.E.)A thread based upon the Whitworth thread form that was established in 1912. A very finethread (a 3/32 inch thread having 60 tpi for example).

MOLYBDENUM DISULPHIDEA solid lubricant that acts as a high pressure resistant film. Can be used by itself as a dry

lubricant as well as in with other solid lubricants and in oils and greases. Used in threads,such lubricants act as a separating film to prevent corrosion formation on the threadsurface (even under adverse temperature and environmental conditions) ensuring therelease of the threaded connection. Such films can also act as friction stabilisers.

NICKED THREADSNicks or indentations in threads can occur during the manufacturing process and duringfastener transportation. In general, nicked thread problems tend to increase as the threaddiameter increases and for fine pitches.

There are acceptance tests for nicked threads that involve measuring the maximum
http://en.wikipedia.org/wiki/File:Screws.jpghttp://en.wikipedia.org/wiki/File:Screws.jpghttp://en.wikipedia.org/wiki/File:Screws.jpghttp://en.wikipedia.org/wiki/File:Screws.jpghttp://en.wikipedia.org/wiki/File:Screws.jpghttp://en.wikipedia.org/wiki/File:Screws.jpghttp://en.wikipedia.org/wiki/File:Screws.jpghttp://en.wikipedia.org/wiki/File:Screws.jpghttp://en.wikipedia.org/wiki/File:Screws.jpghttp://en.wikipedia.org/wiki/File:Screws.jpghttp://en.wikipedia.org/wiki/File:Screws.jpghttp://en.wikipedia.org/wiki/Quarter_(U.S._coin)http://en.wikipedia.org/wiki/Fastenerhttp://en.wikipedia.org/wiki/Helixhttp://en.wikipedia.org/wiki/Screw_threadhttp://en.wikipedia.org/wiki/Screwdriverhttp://en.wikipedia.org/wiki/Bearing_surfacehttp://en.wikipedia.org/wiki/Diameterhttp://en.wikipedia.org/wiki/Screw#cite_note-1http://en.wikipedia.org/wiki/Clockwise_and_counterclockwisehttp://en.wikipedia.org/wiki/Mnemonic_devicehttp://en.wikipedia.org/wiki/Bicycle_pedal#Attachmenthttp://en.wikipedia.org/wiki/Bicyclehttp://en.wikipedia.org/wiki/Bicycle_pedal#Attachmenthttp://en.wikipedia.org/wiki/Bicyclehttp://en.wikipedia.org/wiki/Micrometerhttp://en.wikipedia.org/wiki/Archimedes'_screwhttp://en.wikipedia.org/wiki/File:Screws.jpghttp://en.wikipedia.org/wiki/Quarter_(U.S._coin)http://en.wikipedia.org/wiki/Fastenerhttp://en.wikipedia.org/wiki/Helixhttp://en.wikipedia.org/wiki/Screw_threadhttp://en.wikipedia.org/wiki/Nut_(hardware)http://en.wikipedia.org/wiki/Screwdriverhttp://en.wikipedia.org/wiki/Wrenchhttp://en.wikipedia.org/wiki/Bearing_surfacehttp://en.wikipedia.org/wiki/Set_screwhttp://en.wikipedia.org/wiki/Diameterhttp://en.wikipedia.org/wiki/Screw#cite_note-1http://en.wikipedia.org/wiki/Clockwise_and_counterclockwisehttp://en.wikipedia.org/wiki/Mnemonic_devicehttp://en.wikipedia.org/wiki/Bicycle_pedal#Attachmenthttp://en.wikipedia.org/wiki/Bicyclehttp://en.wikipedia.org/wiki/Micrometerhttp://en.wikipedia.org/wiki/Archimedes'_screw


13/55

torque required to drive a GO gauge down the thread. Examples of acceptance tests areSAE J123 and the Ford Motor specification WA990 1993. Nicks and indentations in threadsare sometimes referred to as gouges.

NOMINAL DIAMETERThe diameter equal to the external diameter of the threads.

NUT DILATIONUnder load, the wedging action of the threads causes dilation of the nut resulting in anincrease in the minor diameter of the nut, and reducing the effective shear areas of boththe external and internal threads.

NUT RUNNERA torque control fastener tightening tool that is usually powered by compressed air. Thedesign of the tool is such that attempts are made to ensure that the applied torque isindependent of joint stiffness.

NYLOC NUTA torque prevailing nut that uses a nylon patented insert to provide

a locking feature. The nylon insert, it is claimed, helps to seal thebolt thread against seepage of water, oil, petrol, paraffin and otherliquids. The nut is covered by UK patent 8028437 and Europeanpatent 81303450-1. Nyloc is a registered trade name of ForestFasteners.

OCTAGON HEADA bolt or screw whose head cross section is a regular polygon with8 sides.

OVERTAPPINGTapping of a thread following a plating operation so that the threadtolerances comply within specification allowing the internal and external threads to

assemble. It is normal practice to overtap the internal rather than the external thread.PILESTerm used in structural engineering for the joint plates.

PITCHThe nominal distance between two adjacent thread roots or crests.

PLYA single thickness of steel forming part of a structural joint.

POOCHINGPooching is a term sometimes used to describe the effect of the area immediately
http://en.wikipedia.org/wiki/Screw#Differentiation_between_bolt_and_screwhttp://en.wikipedia.org/wiki/Screw#Machine_screwshttp://en.wikipedia.org/wiki/Screw#Hex_cap_screwshttp://en.wikipedia.org/wiki/Screw#Lug_bolts_and_head_boltshttp://en.wikipedia.org/wiki/Screw#Lag_screwhttp://en.wikipedia.org/wiki/Screw#Government_standardshttp://en.wikipedia.org/wiki/Screw#Historical_issuehttp://en.wikipedia.org/wiki/Screw#Controlled_vocabulary_versus_natural_languagehttp://en.wikipedia.org/wiki/Screw#Other_distinctionshttp://en.wikipedia.org/wiki/Screw#Types_of_screw_and_bolthttp://en.wikipedia.org/wiki/Screw#Fasteners_with_a_tapered_shank_.28self-threading_screws.29http://en.wikipedia.org/wiki/Screw#Fasteners_with_a_non-tapered_shankhttp://en.wikipedia.org/wiki/Screw#Other_threaded_fastenershttp://en.wikipedia.org/wiki/Screw#Superbolt.2C_or_multi-jackbolt_tensionerhttp://en.wikipedia.org/wiki/Screw#Hanger_screw_or_hanger_bolthttp://en.wikipedia.org/wiki/Screw#Materialshttp://en.wikipedia.org/wiki/Screw#Bolted_jointshttp://en.wikipedia.org/wiki/Screw#Mechanical_classificationshttp://en.wikipedia.org/wiki/Screw#Inchhttp://en.wikipedia.org/wiki/Screw#Metrichttp://en.wikipedia.org/wiki/Screw#Screw_head_shapeshttp://en.wikipedia.org/wiki/Screw#Screw_head_shapeshttp://en.wikipedia.org/wiki/Screw#Types_of_screw_driveshttp://en.wikipedia.org/wiki/Screw#Toolshttp://en.wikipedia.org/wiki/Screw#Thread_standardshttp://en.wikipedia.org/wiki/Screw#Whitworthhttp://en.wikipedia.org/wiki/Screw#Unified_Thread_Standardhttp://en.wikipedia.org/wiki/Screw#Historyhttp://en.wikipedia.org/wiki/Screw#Other_fastening_methodshttp://en.wikipedia.org/wiki/Screw#See_alsohttp://en.wikipedia.org/wiki/Screwhttp://en.wikipedia.org/wiki/Screw#Differentiation_between_bolt_and_screwhttp://en.wikipedia.org/wiki/Screw#Machine_screwshttp://en.wikipedia.org/wiki/Screw#Hex_cap_screwshttp://en.wikipedia.org/wiki/Screw#Lug_bolts_and_head_boltshttp://en.wikipedia.org/wiki/Screw#Lag_screwhttp://en.wikipedia.org/wiki/Screw#Government_standardshttp://en.wikipedia.org/wiki/Screw#Historical_issuehttp://en.wikipedia.org/wiki/Screw#Controlled_vocabulary_versus_natural_languagehttp://en.wikipedia.org/wiki/Screw#Other_distinctionshttp://en.wikipedia.org/wiki/Screw#Types_of_screw_and_bolthttp://en.wikipedia.org/wiki/Screw#Fasteners_with_a_tapered_shank_.28self-threading_screws.29http://en.wikipedia.org/wiki/Screw#Fasteners_with_a_non-tapered_shankhttp://en.wikipedia.org/wiki/Screw#Other_threaded_fastenershttp://en.wikipedia.org/wiki/Screw#Superbolt.2C_or_multi-jackbolt_tensionerhttp://en.wikipedia.org/wiki/Screw#Hanger_screw_or_hanger_bolthttp://en.wikipedia.org/wiki/Screw#Materialshttp://en.wikipedia.org/wiki/Screw#Bolted_jointshttp://en.wikipedia.org/wiki/Screw#Mechanical_classificationshttp://en.wikipedia.org/wiki/Screw#Inchhttp://en.wikipedia.org/wiki/Screw#Metrichttp://en.wikipedia.org/wiki/Screw#Screw_head_shapeshttp://en.wikipedia.org/wiki/Screw#Types_of_screw_driveshttp://en.wikipedia.org/wiki/Screw#Toolshttp://en.wikipedia.org/wiki/Screw#Thread_standardshttp://en.wikipedia.org/wiki/Screw#ISO_metric_screw_threadhttp://en.wikipedia.org/wiki/Screw#Whitworthhttp://en.wikipedia.org/wiki/Screw#British_Association_screw_threadhttp://en.wikipedia.org/wiki/Screw#Unified_Thread_Standardhttp://en.wikipedia.org/wiki/Screw#Manufacturehttp://en.wikipedia.org/wiki/Screw#Historyhttp://en.wikipedia.org/wiki/Screw#Other_fastening_methodshttp://en.wikipedia.org/wiki/Screw#See_alsohttp://en.wikipedia.org/wiki/Screw#References


14/55

surrounding a tapped hole being raised up as a result of the tension from the stud.Tapped holes are often bored out for the first couple of threads to eliminate this problem.

PRELOADThe tension created in a fastener when first tightened. Reduces after a period of time dueto embedding and other factors.

PREVAILING TORQUEThe torque required to run a nut down a thread on certain types of nuts designed to resistvibration loosening. The resistance can be provided by a plastic insert or a noncircularhead.

PREVAILING TORQUE NUTA type of lock nut which has a prevailing torque to assist in preventing self loosening.

There are two main categories of prevailing torque nuts, all metal and nylon insert. Allmetal torque prevailing nuts generally gain a prevailing torque by distorting the threadsat the top of the nut by some means. Nylon insert torque prevailing nuts ultilise a nylon(or other polymer) insert to achieve a prevailing torque.

PROOF LOADThe proof load of a nut is the axially applied load the nut must withstand without threadstripping or rupture. The proof load of a bolt, screw or stud is the specified load theproduct must withstand without permanent set.

PROPERTY CLASSA designation system which defines the strength of a bolt or nut. For metric fasteners,property classes are designated by numbers where increasing numbers generallyrepresent increasing tensile strengths. The designation symbol for bolts consists of twoparts:1. The first numeral of a two digit symbol or the first two numerals of a three digit symbolapproximates 1/100 of the minimum tensile strength in MPa.

2. The last numeral approximates 1/10 of the ratio expressed as a percentage betweenminimum yield stress and minimum tensile stress.Hence a fastener with a property class of 8.8 has a minimum tensile strength of 800 MPaand a yield stress of 0.8x800=640 MPa.

The designation system for metric nuts is a single or double digit symbol. The numeralsapproximate 1/100 of the minimum tensile strength in MPa. For example a nut of propertyclass 8 has a minimum tensile strength of 800 MPa. A bolt or screw of a particularproperty class should be assembled with the equivalent or higher property class of nut toensure that thread stripping does not occur.
http://en.wikipedia.org/wiki/Screw#External_linkshttp://en.wikipedia.org/wiki/Screw#Bibliographyhttp://en.wikipedia.org/wiki/Screw#External_linkshttp://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=1http://en.wikipedia.org/wiki/File:Bolt_(PSF).pnghttp://en.wikipedia.org/wiki/File:Bolt_(PSF).pnghttp://en.wikipedia.org/wiki/File:Bolt_(PSF).pnghttp://en.wikipedia.org/wiki/File:Bolt_(PSF).pnghttp://en.wikipedia.org/wiki/File:DIN6914_UNI5587.jpghttp://en.wikipedia.org/wiki/File:DIN6914_UNI5587.jpghttp://en.wikipedia.org/wiki/File:DIN6914_UNI5587.jpghttp://en.wikipedia.org/wiki/File:DIN6914_UNI5587.jpghttp://en.wikipedia.org/wiki/File:DIN6914_UNI5587.jpghttp://en.wikipedia.org/wiki/File:DIN6914_UNI5587.jpghttp://en.wikipedia.org/wiki/File:DIN6914_UNI5587.jpghttp://en.wikipedia.org/wiki/File:DIN6914_UNI5587.jpghttp://en.wikipedia.org/wiki/File:DIN6914_UNI5587.jpghttp://en.wikipedia.org/wiki/File:DIN6914_UNI5587.jpghttp://en.wikipedia.org/wiki/File:DIN6914_UNI5587.jpghttp://en.wikipedia.org/wiki/File:DIN6914_UNI5587.jpghttp://en.wikipedia.org/wiki/File:DIN6914_UNI5587.jpghttp://en.wikipedia.org/wiki/File:DIN6914_UNI5587.jpghttp://en.wikipedia.org/wiki/File:DIN6914_UNI5587.jpghttp://en.wikipedia.org/wiki/File:DIN6914_UNI5587.jpghttp://en.wikipedia.org/wiki/File:DIN6914_UNI5587.jpghttp://en.wikipedia.org/wiki/File:DIN6914_UNI5587.jpghttp://en.wikipedia.org/wiki/File:DIN6914_UNI5587.jpghttp://en.wikipedia.org/wiki/Machinery's_Handbookhttp://en.wikipedia.org/wiki/File:DIN6914_UNI5587.jpghttp://en.wikipedia.org/wiki/File:DIN6914_UNI5587.jpghttp://en.wikipedia.org/wiki/File:Bolt_(PSF).pnghttp://en.wikipedia.org/wiki/File:Bolt_(PSF).pnghttp://en.wikipedia.org/wiki/Screw#Bibliographyhttp://en.wikipedia.org/wiki/Screw#External_linkshttp://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=1http://en.wikipedia.org/wiki/Machinery's_Handbook


15/55

PRYINGThe amplification of an external force acting on a bolt by a lever action which can occurwhen that force is an eccentric tensile load.

REDUCED SHANK BOLTA bolt whose shank diameter is smaller than the nominal diameter of the bolt (normallythe shank diameter of such a bolt is approximately equal to the effective diameter ofthethread).

RELAXATIONThe loss of clamping force in a bolt that occurs typically without any nut rotationoccurring. Commonly occurs as a result of embedment but can also be due to gasketcreep, metal creep (at elevated temperatures), differential thermal expansion and stressrelaxation.

RIGHTHAND THREADA screw thread that is screwed in by rotating clockwise. The majority of screw threads areright handed.

ROLLED THREADA thread formed by plastically deforming a blank rather than by cutting. The majority ofstandard fasteners have their threads formed by rolling. Most threads are rolled beforeany heat treatment operation. Significant improvements in fatigue life can be achieved byrolling the thread after heat treatment, this improvement is due to compressive stressesbeing induced in the roots of the thread. However, because of the increased hardness ofthe bolt blank, the die life can be significantly reduced. Rolling the thread also generallyimproves the surface finish which can have a beneficial effect on fatigue life.

ROOT DIAMETERIdentical to MINOR DIAMETER

SCREW

A headed threaded fastener that is designed to be used in conjunction with a pre formedinternal thread or alternatively forming its own thread. Historically, it was a threadedfastener with the thread running up to the head of the fastener that has no plain shank.However this definition has largely been superseded to avoid confusion over thedifference between a bolt and a screw.

SCREW THREADA ridge of constant section which is manufactured so that a helix is developed on theinternal or external surface of a cylinder.

SELF LOOSENING
http://en.wikipedia.org/w/index.php?title=ASME_B18.2.1&action=edit&redlink=1http://en.wikipedia.org/wiki/Screw#cite_note-3http://en.wikipedia.org/wiki/Screw#cite_note-4http://en.wikipedia.org/wiki/Screw#cite_note-5http://en.wikipedia.org/wiki/Screw#cite_note-6http://en.wikipedia.org/wiki/Screw#cite_note-7http://en.wikipedia.org/wiki/Screw#cite_note-8http://en.wikipedia.org/wiki/Wikipedia:Verifiabilityhttp://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=2http://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=3http://en.wikipedia.org/wiki/Screw#cite_note-11http://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=4http://www.boltscience.com/pages/glossary.htm#ANGLECONTROLhttp://www.boltscience.com/pages/glossary.htm#ANGLECONTROLhttp://en.wikipedia.org/wiki/Screw#cite_note-2http://en.wikipedia.org/w/index.php?title=ASME_B18.2.1&action=edit&redlink=1http://en.wikipedia.org/wiki/Screw#cite_note-3http://en.wikipedia.org/wiki/Screw#cite_note-4http://en.wikipedia.org/wiki/Screw#cite_note-5http://en.wikipedia.org/wiki/Screw#cite_note-6http://en.wikipedia.org/wiki/Screw#cite_note-7http://en.wikipedia.org/wiki/Screw#cite_note-8http://en.wikipedia.org/wiki/Wikipedia:Verifiabilityhttp://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=2http://en.wikipedia.org/wiki/Screw#cite_note-9http://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=3http://en.wikipedia.org/wiki/Diameterhttp://en.wikipedia.org/wiki/Screw#cite_note-10http://en.wikipedia.org/wiki/Screw#cite_note-11http://en.wikipedia.org/wiki/Screw#cite_note-12http://en.wikipedia.org/wiki/Screw#cite_note-13http://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=4


16/55

Threaded fasteners can come loose on occasions without human intervention. Thisloosening can be due to creep, embedding, stress relaxation or the fastener self-rotating(which is often called vibration loosening). Creep, embedding and stress relaxation willgenerally not completely loosen a fastener, these loosening mechanisms occur withoutthe nut rotating relative to the bolt. The term self loosening is sometimes used for the nutrotating relative to the bolt without human intervention. It is know that the fastener canself rotate under the action of transverse joint movement that can completely loosen atightened fastener such that the nut will become detached from the bolt.

SEMSA screw and washer assembly. A screw or bolt which has a captive washer. The washer isfrequently loose on the plain shank of the fastener, the shank diameter being equal to theeffective diameter ofthe thread; the thread being rolled from this diameter. The origin ofthe word is a frequent question. In the 1930's E. C. Crowther was a representative for acompany that sold both shakeproof washers and screws. He came up with the idea ofplacing the washer on the screw before it was thread rolled. The major diameter of the

screw being larger than the washer hole prevents it from coming off. The Illinois ToolWorks made machines that produced these patented pre-asSEMbled washers and screws.The s at the end of SEMs is thought to have been subsequently picked up because theyare not usually purchased individually. In spite of the original patents and trademarks theword SEMS is generally recognised as a generic term applicable to screw and washerassemblies.

SET SCREWA set screw is a threaded fastener that is typically used to hold a sleeve, collar or gear ona shaft to prevent relative motion. It is a threaded member that normally does not have ahead. Unlike most other threaded fasteners it is basically a compression device normallyused to generate axial thrust. Various socket types are provided to allow the set screw to

be rotated. These types include hexagon socket, fluted socket, screwdriver slot andsquare head. Various point designs are available (the part of the set screw that rotatesagainst the shaft being secured) and include:Cup - Hollowed end, is the most commonly used point style. Used when the digging in ofthe point is not undesirable.Cone - Pointed end, this type generates the highest torsional holding power and istypically used for a permanent connection.Oval - Rounded end that is typically used when frequent adjustment is required. The ovalend prevents/reduces indentation.
http://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=5http://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_001.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_001.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_001.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_001.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_001.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_001.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_001.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_001.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_001.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_001.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_001.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_001.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_001.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_001.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_001.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_001.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_002.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_002.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_002.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_002.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_002.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_002.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_002.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_002.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_002.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_002.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_002.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_002.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_001.pnghttp://en.wikipedia.org/wiki/File:Lag_screws_aka_lag_bolts_001.pnghttp://www.boltscience.com/pages/glossary.htm#ahttp://www.boltscience.com/pages/glossary.htm#bhttp://www.boltscience.com/pages/glossary.htm#chttp://www.boltscience.com/pages/glossary.htm#dhttp://www.boltscience.com/pages/glossary.htm#ehttp://www.boltscience.com/pages/glossary.htm#fhttp://www.boltscience.com/pages/glossary.htm#ghttp://www.boltscience.com/pages/glossary.htm#hhttp://www.boltscience.com/pages/glossary.htm#ihttp://www.boltscience.com/pages/glossary.htm#jhttp://www.boltscience.com/pages/glossary.htm#khttp://www.boltscience.com/pages/glossary.htm#lhttp://www.boltscience.com/pages/glossary.htm#mhttp://www.boltscience.com/pages/glossary.htm#nhttp://www.boltscience.com/pages/glossary.htm#ohttp://www.boltscience.com/pages/glossary.htm#phttp://www.boltscience.com/pages/glossary.htm#qhttp://www.boltscience.com/pages/glossary.htm#rhttp://www.boltscience.com/pages/glossary.htm#shttp://www.boltscience.com/pages/glossary.htm#thttp://www.boltscience.com/pages/glossary.htm#uhttp://www.boltscience.com/pages/glossary.htm#vhttp://www.boltscience.com/pages/glossary.htm#whttp://www.boltscience.com/pages/glossary.htm#whttp://www.boltscience.com/pages/glossary.htm#whttp://www.boltscience.com/pages/glossary.htm#whttp://en.wikipedia.org/wiki/Screw#cite_note-14http://en.wikipedia.org/wiki/Screw#cite_note-15http://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=5


17/55

Flat - Cause little damage to the shaft and are used when frequent adjustment is required.

Dog - Flat end with the threads stopping short of the end with the end fitting into a hole.SHANK

That portion of a bolt between the head and the threaded portion.SHOULDER SCREWS

A threaded fastener with a plain, precision machined, shank that is used for locationpurposes. They are typically used for pulleys and linkages.

SKIDMORE BOLT TENSION CALIBRATORThe Skidmore-Wilhelm bolt tension calibrator is a hydraulic load cell used to determinethe tension in a bolt or other threaded fastener. The tension in the bolt compresses fluidin a hydraulic cylinder, a pressure gauge connected to the cylinder is then calibrated toread in terms of force rather than pressure.

SNUG TORQUEThe torque required to pull plates together so that direct contact occurs; often used inangle control tightening. The snug torque ensures that metal to metal contact occurs atall the interfaces within the joint. It is only at this point that the required angle of rotationstart in order that the bolt is tightened sufficiently. The snug torque is usually determinedexperimentally on the actual joint.

SNUGGINGThe process of pulling parts of a joint together, most of the input turn during this processis absorbed in the joint with little tension being given to the bolt.

SOCKET HEAD CAP SCREWA screw with a round head, usually with a hexagon indentation in the head for tighteningpurposes. Used on machine parts and is typically made from high strength steel (grade12.9 in metric).

SOFT JOINTA joint in which the plates and material between the nut and bolt bearing surfaces have alow stiffness when subjected to compression by the bolt load. In such a joint, the bolt (ornut) typically has to be tightened by two or more complete turns, after it has beentorqued to the snug condition, before the full tightening torque is achieved. Often theplacement of a gasket in a joint results in a soft joint.

SOFT TORQUEAn alternative name, used by some manufacturers, for snug torque.
http://en.wikipedia.org/wiki/Hot-dip_galvanizinghttp://en.wikipedia.org/wiki/Screw#cite_note-16http://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=6http://en.wikipedia.org/wiki/US_governmenthttp://en.wikipedia.org/wiki/US_governmenthttp://en.wikipedia.org/wiki/Engineering_tolerancehttp://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=7http://en.wikipedia.org/wiki/Society_of_Automotive_Engineershttp://en.wikipedia.org/wiki/Society_of_Automotive_Engineershttp://en.wikipedia.org/wiki/Screw#cite_note-dyke-18http://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=8http://en.wikipedia.org/wiki/Controlled_vocabularyhttp://en.wikipedia.org/wiki/Standards_organizationhttp://en.wikipedia.org/wiki/Natural_languagehttp://en.wikipedia.org/wiki/Retronymhttp://en.wikipedia.org/wiki/Galvanizationhttp://en.wikipedia.org/wiki/Hot-dip_galvanizinghttp://en.wikipedia.org/wiki/Screw#cite_note-16http://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=6http://en.wikipedia.org/wiki/US_governmenthttp://en.wikipedia.org/wiki/Tariffshttp://en.wikipedia.org/wiki/Screw#cite_note-CBP.gov_bolts-vs-screws-17http://en.wikipedia.org/wiki/Engineering_tolerancehttp://en.wikipedia.org/wiki/Screw_thread#Coarse_versus_finehttp://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=7http://en.wikipedia.org/wiki/United_States_Standardhttp://en.wikipedia.org/wiki/Society_of_Automotive_Engineershttp://en.wikipedia.org/wiki/Screw#cite_note-dyke-18http://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=8http://en.wikipedia.org/wiki/Controlled_vocabularyhttp://en.wikipedia.org/wiki/Standards_organizationhttp://en.wikipedia.org/wiki/Natural_languagehttp://en.wikipedia.org/wiki/History_of_technologyhttp://en.wikipedia.org/wiki/Retronym


18/55

SPIRAL WOUND GASKETA type of gasket that is made by winding V-section metal strip and a softer filler materialtogether. Support or retaining rings, inside and/or outside the spiral, improve the gasket'shandling and fitting. The filler material used is typically graphite or PTFE. The metal stripand retaining rings being typically made from stainless steel.

STATIC FRICTIONFriction at rest; a force is required to initiate relative movement between two bodies -static friction is the force that resists such relative movement. Sometimes referred to asstiction.

STEP-LOCK BOLT (SLB)The Step-Lock Bolt (SLB) is a thread form that has been modified to resist vibrationloosening. The thread has several horizontal portions (i.e. no lead angle) whose purpose isto prevent torsion being developed in the bolt as a result of the loosening purpose. It isthese horizontal portions that are known as steps. Published literature indicates that thethread form performs well when tested on a transverse vibration test machine. Howevermanufacturing difficulties may prevent its widespread adoption.

STIFFNUTA term used to describe a lock nut which has a prevailing torque.

STRENGTH GRADESee PROPERTY CLASS

STRESS AREAThe effective cross sectional area of a thread when subjected to a tensile force. It is basedupon a diameter which is the mean of the pitch (or effective) and the minor (or root)diameters of the thread. The use of this diameter stems from the work of E. M. Slaughterin the 1930's. He completed carefully controlled tests using various sizes of standardthreads and compared their strength with machined bars made from the same bar of

material. He found that this mean diameter gave results that agreed with the tensile testresults to within about 3%. The error on the minor and pitch diameters was about 15%.Tests completed subsequent to these by other investigators have also shown that thestress diameter is a reasonable approximation to a thread's tensile strength. (Referance:'Tests on Thread Sections Show Exact Strengthening Effect of Threads.' by E. M.Slaughter, Metal Progress, vol 23, March 1933 pp. 18-20)

STRESS RELAXATIONA significant problem with bolting at high temperatures is a phenomenon known as stressrelaxation. Creep occurs when a material is subjected to high temperature and a constant
http://en.wikipedia.org/wiki/Gimlet_(tool)http://en.wikipedia.org/wiki/Crossbowhttp://en.wikipedia.org/wiki/Clinker_(boat_building)#Fastening_the_centre-line_structurehttp://en.wikipedia.org/wiki/Cylinder_headhttp://en.wikipedia.org/wiki/Natural_languagehttp://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=9http://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=9http://en.wikipedia.org/wiki/ISO_metric_screw_threadhttp://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=10http://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=10http://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=11http://en.wikipedia.org/wiki/Gimlet_(tool)http://en.wikipedia.org/wiki/Crossbowhttp://en.wikipedia.org/wiki/Clinker_(boat_building)#Fastening_the_centre-line_structurehttp://en.wikipedia.org/wiki/Cylinder_headhttp://en.wikipedia.org/wiki/Natural_languagehttp://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=9http://en.wikipedia.org/wiki/ISO_metric_screw_threadhttp://en.wikipedia.org/wiki/Unified_Thread_Standardhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=10http://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=11


19/55

load. Stress relaxation occurs when a high stress is present that is relieved over time; thestress is relaxed with a subsequent reduction in the bolts preload. The only way tominimise the effects of stress relaxation is to use materials that have an adequateresistance to it at the products operating temperature. The effect of bolt stress relaxationis to reduce the clamp force provided by the bolts; this phenomena alone will not fullyloosen a joint.

STRUCTURAL BOLTA structural bolt is a heavy hexagon head bolt having a controlled thread length intendedfor use in structural connections and assembly of such structures as buildings andbridges. The controlled thread length is to enable the thread to stop before the joint plyinterface to improve the fastener's direct shear performance.This term is used in civil andstructural engineering but is not frequently used in mechanical engineering.

STUDA fastener which is threaded at both ends with an unthreaded shank in between. One end(which often has a thread tolerance which results in more thread interference) is securedinto a tapped hole, the other is used with a nut.

SYMMETRICAL THREADA symmetrical thread is one which has both flanks of the thread profile inclined at thesame angle.

TAYLOR-FORGE METHODA method developed by four engineers of the Taylor-Forge Company in Chicago in the1930's that subsequently formed the basis of the ASME code for flanged joint design. Theassumptions made by the method are now generally regarded as too simplistic. Thismethod gives rise to the m and y gasket factors.

TENSION WASHERS

A general name given to spring washers, curved washers, Belleville washers and discsprings. This type of washer provides a relatively low stiffness (compared to the jointstiffness) and can be used to act as a spring take-up with a bolt to prevent movementbetween parts.

THREAD CRESTThe top part of the thread. For external threads, the crest is the region of the threadwhich is on it's outer surface, for internal threads it is the region which forms the innerdiameter.

THREAD FLANK
http://en.wikipedia.org/wiki/File:Stockschraube.jpghttp://en.wikipedia.org/wiki/File:Stockschraube.jpghttp://en.wikipedia.org/wiki/File:Screw.agr.jpghttp://en.wikipedia.org/wiki/File:Screw.agr.jpghttp://en.wikipedia.org/wiki/File:Screw.agr.jpghttp://en.wikipedia.org/wiki/File:Screw.agr.jpghttp://en.wikipedia.org/wiki/File:Screw.agr.jpghttp://en.wikipedia.org/wiki/File:Stockschraube.jpghttp://en.wikipedia.org/wiki/Screw#cite_note-19http://en.wikipedia.org/wiki/Hammer_drill


20/55

The thread flanks join the thread roots to the crest.THREAD HEIGHT

This is the distance between the minor and major diameters of the thread measuredradially.

THREAD LENGTHLength the portion of the fastener with threads.

THREAD ROOTThe thread root is the bottom of the thread, on external threads the roots are usuallyrounded so that fatigue performance is improved.

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

THREADLOCKERCan be a term used for a number of vibration resistant products but is now usuallyreserved for threadlocking adhesives. Specifically, a liquid anaerobic adhesive applied tonut or bolt thread, once hardened it fills the inner spaces between the threads to producea solid plastic of a known shear strength.

TIN/ZINC ALLOY ELECTROPLATINGTin/zinc alloy coatings (typically 70% tin and 30% zinc) are applied to threaded fastenersto provide a corrosion resistant coating. One of the advantages of such coatings is thatbimetallic corrosion will not occur when placed into contact with such metals asaluminium or steel.

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

TOLERANCE GRADEThe difference between maximum and minimum metal conditions for a tolerance appliedto a screw thread. For metric threads the tolerance grade is given a number.

TORQUEA rotational moment; it is a measure of how much twisting is applied to a fastener. Theunits used to measure torque are in the form of force times length. Usually measured innewton-metres (Nm) if metric units are used or pounds feet (lb-ft) when imperial units areused.

TORQUE MULTIPLIER
http://en.wikipedia.org/wiki/File:Eye_bolt_wood_thread.jpghttp://en.wikipedia.org/wiki/File:Eye_bolt_wood_thread.jpghttp://en.wikipedia.org/wiki/File:Eye_bolt_wood_thread.jpghttp://en.wikipedia.org/wiki/File:Eye_bolt_wood_thread.jpghttp://en.wikipedia.org/wiki/File:Eye_bolt_wood_thread.jpghttp://en.wikipedia.org/wiki/File:Tire-fond_cropped.JPGhttp://en.wikipedia.org/wiki/File:Tire-fond_cropped.JPGhttp://en.wikipedia.org/wiki/File:Tire-fond_cropped.JPGhttp://en.wikipedia.org/wiki/File:Tire-fond_cropped.JPGhttp://en.wikipedia.org/wiki/Screw#cite_note-20http://en.wikipedia.org/wiki/File:Tire-fond_cropped.JPGhttp://en.wikipedia.org/wiki/File:Mirror_Screws.jpghttp://en.wikipedia.org/wiki/File:Mirror_Screws.jpghttp://en.wikipedia.org/wiki/File:Mirror_Screws.jpghttp://en.wikipedia.org/wiki/File:Mirror_Screws.jpghttp://en.wikipedia.org/wiki/File:Mirror_Screws.jpghttp://en.wikipedia.org/wiki/File:Phillips_screw.jpghttp://en.wikipedia.org/wiki/File:Phillips_screw.jpghttp://en.wikipedia.org/wiki/File:Phillips_screw.jpghttp://en.wikipedia.org/wiki/File:Phillips_screw.jpghttp://en.wikipedia.org/wiki/File:Phillips_screw.jpghttp://en.wikipedia.org/wiki/File:Phillips_screw.jpghttp://en.wikipedia.org/wiki/File:Mirror_Screws.jpghttp://en.wikipedia.org/wiki/File:Tire-fond_cropped.JPGhttp://en.wikipedia.org/wiki/File:Eye_bolt_wood_thread.jpghttp://en.wikipedia.org/wiki/Screw#cite_note-20http://en.wikipedia.org/wiki/Timber_framing


21/55

A gearbox used to increase the torque produced by a small hand wrench.TORQUE WRENCH

A manual wrench which incorporates a gauge or other method to indicate the amount oftorque transferred to the nut or bolt.

TURN OF THE NUT METHODSee ANGLE CONTROLLED TIGHTENING

U BOLTA U shaped fastener threaded at both ends used primarily in suspension and related areasof vehicles.

ULTRASONIC EXTENSOMETERAn instrument which can measure the change in length of a fastener ultrasonically as thefastener is tightened or measure the length before and after it is tightened).

UNCUnified National Coarse (UNC) is a thread form with a 60 degree flank angle rounded rootsand flat crests. For a given diameter it has a larger thread pitch than an equivalentdiameter UNF thread. The unified thread is based on inch sizes and was first standardisedin 1948 unifying the Whitworth and American standard thread forms.

UNEFUnified National Extra Fine (UNEF) is a Unified thread form with a very fine (small) pitchthat are typically used on instruments and parts requiring a fine adjustment.

UNFUnified National Fine (UNF) is a thread form with a 60 degree flank angle rounded rootsand flat crests. For a given diameter it has a smaller thread pitch than an equivalentdiameter UNC thread.

UNRUnified National (UN) thread form with a rounded root contour, applies only to external

threads. (The UN thread form has a flat, or optionally, a rounded root contour.) Themajority of fasteners with a Unified thread form have a rounded root contour i.e. are UNRthreads.

VIRTUAL EFFECTIVE DIAMETERThe effective diameter of a thread but allowing for errors in pitch and flank angles.

WAISTED SHANK BOLTA bolt whose diameter is less than the minor diameter of the thread. Frequently the shankof the bolt is 0.9 times the root diameter.
http://en.wikipedia.org/wiki/Lead_(engineering)http://en.wikipedia.org/wiki/File:Screw_for_wood.JPGhttp://en.wikipedia.org/wiki/File:Screw_for_wood.JPGhttp://en.wikipedia.org/wiki/File:Screw_for_wood.JPGhttp://en.wikipedia.org/wiki/File:Screw_for_wood.JPGhttp://en.wikipedia.org/wiki/File:Screw_for_wood.JPGhttp://en.wikipedia.org/wiki/File:Screw_for_wood.JPGhttp://en.wikipedia.org/wiki/File:Screw_for_wood.JPGhttp://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=12http://en.wikipedia.org/wiki/File:AnchorBolt_M12_01.jpghttp://en.wikipedia.org/wiki/File:AnchorBolt_M12_01.jpghttp://en.wikipedia.org/wiki/File:AnchorBolt_M12_01.jpghttp://en.wikipedia.org/wiki/File:AnchorBolt_M12_01.jpghttp://en.wikipedia.org/wiki/File:Vis_6_pans_creux_coupee.JPGhttp://en.wikipedia.org/wiki/File:Vis_6_pans_creux_coupee.JPGhttp://en.wikipedia.org/wiki/File:Vis_6_pans_creux_coupee.JPGhttp://en.wikipedia.org/wiki/File:Vis_6_pans_creux_coupee.JPGhttp://en.wikipedia.org/wiki/File:AnchorBolt_M12_01.jpghttp://en.wikipedia.org/wiki/File:Screw_for_wood.JPGhttp://en.wikipedia.org/wiki/Lead_(engineering)http://en.wikipedia.org/wiki/Screw#cite_note-21http://en.wikipedia.org/wiki/Screw#cite_note-22http://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=12


22/55

WIRE THREAD INSERTA threaded insert that is typically used for tapped hole repair or to improve the threadstripping strength of softer metals such as zinc and aluminium. The inserts are assembledinto a previously tapped hole using a special driving tool. A thread locking compound isfrequently used to secure the insert if the assembly is subject to vibration.

YIELD CONTROLLED TIGHTENINGA fastener tightening method which allows a fastener to be tightened to yield. The angleof rotation of the fastener is measured relative to the applied torque, yield being assessedwhen the slope of the relationship changes to below a certain value. Sometimes called

joint controlled tightening.ZINC ELECTROPLATING

Zinc electroplating is a common way to protect threaded fasteners from the effects ofcorrosion. Zinc electroplating can be completed in acid chloride, alkaline or cyanide baths.Supplemental coatings are frequently applied to zinc electroplating. These coatings, suchas zinc phosphate or chromate conversion, provide a protective passivation layer on thezinc which assists in reducing the corrosion rate.

ZINC/COBALT ALLOY ELECTROPLATINGThis coating is similar to zinc electroplating completed in an acid chloride bath - a smallamount of cobalt (typically about 1%) is added to increase the plating speed.

ZINC PHOSPHATE CONVERSION COATINGA zinc phosphate conversion coating is frequently added to zinc electroplated parts, suchas bolt threads, to improve corrosion resistance. This type of chemical conversion coatingprovides a protective passivation layer on the zinc improving its corrosion resistance.

A | B | C | D | E | F | G | H | I | J | K| L | M | N | O | P | Q | R| S | T | U | V | W | X | Y | Z

| Home | About Us | Software | Services |Training | Download | Pricing | Bolting Info |

Copyright 1996-2013 Bolt Science Limited. All Rights ReservedFor more information on any of our products or services please feel free to Contact Us
http://en.wikipedia.org/wiki/Screw#cite_note-23http://en.wikipedia.org/wiki/Screw#cite_note-24http://en.wikipedia.org/wiki/File:Tornillo_(Tipos_de_cabeza).pnghttp://en.wikipedia.org/wiki/File:Tornillo_(Tipos_de_cabeza).pnghttp://en.wikipedia.org/wiki/Screw#cite_note-26http://en.wikipedia.org/wiki/Real_versus_nominal_valuehttp://en.wikipedia.org/wiki/Real_versus_nominal_valuehttp://en.wikipedia.org/wiki/Alloyhttp://en.wikipedia.org/wiki/File:Tornillo_(Tipos_de_cabeza).pnghttp://en.wikipedia.org/wiki/File:Tornillo_(Tipos_de_cabeza).pnghttp://en.wikipedia.org/wiki/File:Vis_6_pans_creux_coupee.JPGhttp://en.wikipedia.org/wiki/Screw#cite_note-23http://en.wikipedia.org/wiki/Screw#cite_note-24http://en.wikipedia.org/wiki/Screw#cite_note-25http://en.wikipedia.org/wiki/Screw#cite_note-26http://en.wikipedia.org/wiki/Screw#cite_note-dyke-18http://en.wikipedia.org/wiki/Real_versus_nominal_valuehttp://en.wikipedia.org/wiki/Major_diameterhttp://en.wikipedia.org/wiki/Forginghttp://en.wikipedia.org/wiki/Heat_treathttp://en.wikipedia.org/wiki/Alloy


23/55

http://www.gizmology.net/nutsbolts.htm

Notes on Nuts and Bolts

A screw thread is a helical groove on a shaft. When used for delivering power, it is called a drive screw. Drive screws aren't really all

that efficient, as they loose a significant amount of power to friction. However, this friction can be put to use in the case ofthreadedfasteners. You might say that a drive screw is an inclined plane wrapped around a post, while a fastener is a wedge wrapped around a

post.

Bolt Terms

A 1/2-13UNC-2A-3 bolt, with a 2" thread and a 1" shank.

As nuts and bolts are not perfectly rigid, but stretch slightly under load, the distribution of stress on the threads is not uniform. In fact,

on a theoretically infinitely long bolt, the first thread takes a third of the load, the first three threads take three-quarters of the load, andthe first six threads take essentially the whole load. Beyond the first six threads, the remaining threads are under essentially no load at

all. Therefore, a nut or bolt with six threads acts very much like an infinitely long nut or bolt (and it's a lot cheaper).
http://en.wikipedia.org/wiki/Countersinkhttp://en.wikipedia.org/wiki/Hex_keyhttp://en.wikipedia.org/wiki/Hex_keyhttp://en.wikipedia.org/wiki/Hex_driverhttp://en.wikipedia.org/wiki/File:Bout.jpghttp://en.wikipedia.org/wiki/File:Bout.jpghttp://en.wikipedia.org/wiki/File:Bout.jpghttp://en.wikipedia.org/wiki/File:Bout.jpghttp://en.wikipedia.org/wiki/File:Elevatorbolt.jpghttp://en.wikipedia.org/wiki/File:Carriage_bolts.jpghttp://en.wikipedia.org/wiki/Countersinkhttp://en.wikipedia.org/wiki/Hex_keyhttp://en.wikipedia.org/wiki/Hex_driverhttp://en.wikipedia.org/wiki/Hex_driverhttp://en.wikipedia.org/wiki/Socket_wrenchhttp://en.wikipedia.org/wiki/Screw#cite_note-27


24/55

Stress on bolt threads. Note how the majority of

the stress is on the first thread to the left.Image from Spiralock.

Thread

%%Sum

134%

34%

2

23

% 55%

316%

71%

411%

82%

5 9% 91%

6 7% 98%

There is little point in having more than six threads in anything. Nuts with National Coarse threads typically have 5 threads in them,

whereas nuts with National Fine threads have about 8 threads. Nuts are usually stronger than the bolts they are on, which is to say that

the bolt will usually break before the nut strips.

It is often said that two threads must be exposed above a nut. The reason for this is that the first two threads of a bolt are often poorly

formed, and may not engage the nut properly. If they're not doing their share, the other threads in the nut will be overloaded, and the

nut may strip.

Thread Terms

Metric and American threads both conform to the same profile, a series of equilateral triangles with the crests chopped off and the

roots rounded.
http://en.wikipedia.org/wiki/File:Vis-auto-taraudeuse.jpeghttp://en.wikipedia.org/wiki/File:Vis-auto-foreuse.jpeghttp://en.wikipedia.org/wiki/File:100_TPI_fine_adjustment_screw_with_close_up,_Oct_2012.jpghttp://en.wikipedia.org/wiki/Fine_adjustment_screwhttp://en.wikipedia.org/wiki/Fine_adjustment_screwhttp://en.wikipedia.org/wiki/Screw#cite_note-28http://en.wikipedia.org/wiki/Screw#cite_note-29http://en.wikipedia.org/wiki/Screw#cite_note-30


25/55

External Standard Thread Profile

The depth of the threads is 54.127% of the distance between threads, and the radius of the rounded root is 14.434% of the distance

between threads. Another way of looking at it would be to say that 1/8 of the height of each equilateral triangle is chopped off the top,and 1/4 of the height off the bottom, leaving only

5/8 of the height available. (The height of an equilateral triangle is equal to the width

times half of the square root of three; 5/8 of this is 0.54127.)

The root diameter of the thread is the nominal diameter minus 108.3% of the pitch of the thread. This means that fine threads have

larger root diameters than coarse threads, and thus larger tap drill sizes. For threading using a tap or die, most threads are not cut tofull depth, but to 75% or so. The resulting threads are not quite as strong, but full depth threading is very hard on the tap or die.

Threading on a lathe presents no difficulty cutting to full depth.

Thread Specifications

Thread specifications are written thus:

1/2-13UNC-2
http://en.wikipedia.org/wiki/Mechanism_(engineering)http://en.wikipedia.org/wiki/Linkage_(mechanical)http://en.wikipedia.org/wiki/Stripper_platehttp://en.wikipedia.org/wiki/Die_(manufacturing)http://en.wikipedia.org/wiki/File:Setscrews_(PSF).pnghttp://en.wikipedia.org/wiki/Set_screwhttp://en.wikipedia.org/wiki/Alloyhttp://en.wikipedia.org/wiki/Heat_treathttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Mechanism_(engineering)http://en.wikipedia.org/wiki/Linkage_(mechanical)http://en.wikipedia.org/wiki/Stripper_platehttp://en.wikipedia.org/wiki/Die_(manufacturing)


26/55

which means:

bolt diameter threads per inch thread type fit class

There are four Fit Classes, ranging from falling-off-loose to scientific-instrument-tight.

Class 1 = Loose Class 2 = Free Class 3 = Medium Class 4 = Close

The class is followed by an A for external (screw) threads and a B for internal (nut) threads. Most are class 2. 3 is for precision

assembly, and 4 is used for things like lathe lead screws and measuring instruments.

In November 1948, NATO issued a new standard for threads, the Unified National system. American bolts had flat-bottomed grovesbetween threads, which interfered with British round-topped threads. Likewise, British bolts wouldn't fit American nuts. The Unified

system uses a round-bottom grove to fit the British threads, and a flat-topped thread to fit the American threads, so it not only fit itself,

but both existing systems.

American/United National Threads

Size

Diameter

TPICoarse

TPIFine

RootDia.Coars

e

HexHead

Size

SAEWasherID

SAEWasher

OD

SAE

Washer

Thickness

#0 0.0600 - 80 0.0447

#1 0.0730 64 72 0.0560

#2 0.0860 56 64 0.0668 3/32" 1/4" 1/32"

#3 0.0990 48 56 0.0771
http://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=15http://en.wikipedia.org/wiki/Screw#cite_note-31http://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=13http://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=14http://en.wikipedia.org/wiki/Multi-jackbolt_tensionerhttp://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=15


27/55

#4 0.1120 40 48 0.0813 1/8" 5/16" 1/32"

#5 0.1250 40 44 0.0971

#6 0.1380 32 40 0.1073 5/32" 3/8" 3/64"

#8 0.1640 32 36 0.1299 3/16" 7/16" 3/64"

#10

0.1900 24 32 0.1570 7/32" 1/2" 1/16"

#12

0.2160 24 28 0.1722 1/4" 9/16" 1/16"

1/4" 0.2500 20 28 0.1850 3/8" 9/32" 5/8" 1/16"5/16"

0.3125 18 24 0.2400 1/2" 11/32" 11/16" 1/16"

3/8" 0.3750 16 24 0.2940 9/16" 13/32" 13/16" 1/16"7/16" 0.4375 14 20 0.3440

5

/8"15

/32"15

/16"1

/16"1/2" 0.5000 13 20 0.4000 3/4" 17/32" 1-1/16" 3/32"9/16"

0.5625 12 18 0.4540 7/8" 19/32" 1-3/16" 3/32"

5/8" 0.6250 11 18 0.5070 15/16" 21/32" 1-5/16" 3/32"3/4" 0.7500 10 16 0.6200 1-1/8" 13/16" 1-1/2" 1/8"

7/8" 0.8750 9 14 0.73101-

5/16"15/16" 1-3/4" 1/8"

1" 1.0000 8 12 0.8370 1-1

/2" 1-1

/16" 1-3

/4"1

/8"

A much more complete table is available here.

Metric Threads

Metric threads use the same thread profile as SAE threads. The biggest difference is that the thread pitch (distance between

consecutive threads) is given instead of threads per unit distance.
http://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Brasshttp://en.wikipedia.org/wiki/Titaniumhttp://en.wikipedia.org/wiki/Bronzehttp://en.wikipedia.org/wiki/Nylonhttp://en.wikipedia.org/wiki/Polytetrafluoroethylenehttp://en.wikipedia.org/wiki/Polytetrafluoroethylenehttp://en.wikipedia.org/wiki/Polytetrafluoroethylenehttp://en.wikipedia.org/wiki/Polytetrafluoroethylenehttp://en.wikipedia.org/wiki/Electrical_insulationhttp://en.wikipedia.org/wiki/File:Rustybolt_th.jpghttp://en.wikipedia.org/wiki/File:Rustybolt_th.jpghttp://en.wikipedia.org/wiki/File:Rustybolt_th.jpghttp://en.wikipedia.org/wiki/File:Rustybolt_th.jpghttp://en.wikipedia.org/wiki/File:Rustybolt_th.jpghttp://en.wikipedia.org/wiki/File:Rustybolt_th.jpghttp://en.wikipedia.org/wiki/File:Rustybolt_th.jpghttp://en.wikipedia.org/wiki/File:Rustybolt_th.jpghttp://en.wikipedia.org/wiki/File:Rustybolt_th.jpghttp://en.wikipedia.org/wiki/File:Rustybolt_th.jpghttp://en.wikipedia.org/wiki/File:Rustybolt_th.jpghttp://en.wikipedia.org/wiki/File:Rustybolt_th.jpghttp://en.wikipedia.org/wiki/American_Institute_of_Steel_Constructionhttp://en.wikipedia.org/wiki/American_Institute_of_Steel_Constructionhttp://en.wikipedia.org/wiki/AISChttp://en.wikipedia.org/wiki/File:Rustybolt_th.jpghttp://en.wikipedia.org/wiki/File:Rustybolt_th.jpghttp://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=16http://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Brasshttp://en.wikipedia.org/wiki/Titaniumhttp://en.wikipedia.org/wiki/Bronzehttp://en.wikipedia.org/wiki/Galvanic_corrosionhttp://en.wikipedia.org/wiki/Aluminiumhttp://en.wikipedia.org/wiki/Nylonhttp://en.wikipedia.org/wiki/Polytetrafluoroethylenehttp://en.wikipedia.org/wiki/Electrical_insulationhttp://en.wikipedia.org/wiki/Japanninghttp://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=17http://en.wikipedia.org/wiki/Bolted_jointhttp://en.wikipedia.org/wiki/American_Institute_of_Steel_Constructionhttp://en.wikipedia.org/wiki/AISC


28/55

Diameter

Coarse

Pitch

mm

Fine

Pitchm

m

RootDia.

Coarse

mm

HexHeadSize

mm

ISOWash

erID

mm

ISOWash

erOD

mm

ISOWashe

rThickn

ess

mm

1 0.25 0.7294

1.1 0.25 0.8294

1.2 0.25 0.9294

1.4 0.30 1.075

1.6 0.35 1.221 3.2

1.8 0.35 1.421

2 0.40 1.567 4

2.2 0.45 1.7132.5 0.45 2.013 5

3 0.50 2.459 5.5 3.4 7.0 0.6

3.5 0.60 2.850

4 0.700.50

3.242 7 4.5 9.0 0.9

4.5 0.750.50

3.688

5 0.80

0.5

0 4.134 8 5.5 10 11

5.50.50

6 1.000.50

4.917 10 6.7 12.5 1.8

7 1.000.75

5.917
http://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=18http://en.wikipedia.org/wiki/International_Organization_for_Standardizationhttp://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=18http://en.wikipedia.org/wiki/International_Organization_for_Standardizationhttp://en.wikipedia.org/wiki/Ultimate_tensile_strengthhttp://en.wikipedia.org/wiki/Megapascalhttp://en.wikipedia.org/wiki/Yield_strength#Definitionhttp://en.wikipedia.org/wiki/Counterfeithttp://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=19


29/55

8 1.250.75

6.647 13 8.7 17 1.8

9 1.250.75

7.647

10 1.50 0.75 8.376 16 10.9 21 2.2

11 1.500.75

9.376

12 1.750.75

10.11 18 13.4 24 2.7

14 2.001.00

11.83 21

16 2.001.00

13.83 24 17.4 30 3.3

18 2.501.00

15.29

20 2.501.00

17.29 30 21.5 37.9 3.3

Bolt Strength

The Society of Automotive Engineering has issued standard J429, which sets forth standards for both strength. The SAE grade of abolt is marked on it's head in the form of short radial lines, the number of lines being two less than the SAE grade (i.e.. 3 lines for

grade 5).

SAEGrade

SizeRange

Strength(psi)

1 1/4" to 1-1/2" 60,000

2 1/4" to 3/4" 74,000

2 7/8" to 1-1/2" 60,000

5 1/4" to 1" 120,000
http://en.wikipedia.org/wiki/Screw#cite_note-siu-32http://en.wikipedia.org/wiki/Screw#cite_note-33http://en.wikipedia.org/wiki/ISO_898http://en.wikipedia.org/w/index.php?title=SAE_J1199&action=edit&redlink=1http://en.wikipedia.org/wiki/Screw#cite_note-F568M-42http://en.wikipedia.org/wiki/Screw#cite_note-metrichandbook-43http://en.wikipedia.org/w/index.php?title=SAE_J429&action=edit&redlink=1http://en.wikipedia.org/wiki/Screw#cite_note-siu-32http://en.wikipedia.org/wiki/Screw#cite_note-33http://en.wikipedia.org/wiki/Screwhttp://en.wikipedia.org/wiki/Screw#cite_note-boltdepot-34http://en.wikipedia.org/w/index.php?title=Screw&action=edit&section=20http://en.wikipedia.org/wiki/ISO_898http://en.wikipedia.org/w/index.php?title=SAE_J1199&action=edit&redlink=1http://en.wikipedia.org/wiki/ASTM_F568Mhttp://en.wikipedia.org/wiki/Screw#cite_note-41http://en.wikipedia.org/wiki/Screw#cite_note-F568M-42http://en.wikipedia.org/wiki/Screw#cite_note-metrichandbook-43http://en.wikipedia.org/wiki/Screwhttp://en.wikipedia.org/wiki/Screw#cite_note-metrichandbook-43


30/55

51-1/8" to 1-

1/2"105,000

7 1/4" to 1-1/2" 133,000

8 1/4" to 1-1/2" 150,000

ASTM standards are sometimes used as well; A325 bolts are the equivalent of SAE 5, and A490 bolts are the equivalent of SAE 8.

Preload

A very misunderstood part of bolting stuff together is preload, which is the tension placed on the bolt by the nut (as opposed to theload). A sufficiently high preload will protect the bolt from fat igue as the load changes, as the varying load will change the clamping

force on the bolted components, rather than the tension on the bolt. (This is not strictly true, but for a tinkerer like me, it's adequate.)As a rule of thumb, the preload should exceed the maximum load by 15% or so.

In order for this to work, however, the joint must be stiffer than the bolt. For this reason, the shank of high-tech bolts are often neckeddown to the same diameter of the root of the thread. As long as it isn't thinner than the root of the thread, it isn't any weaker than the

thread, and therefore doesn't effect overall bolt strength, but it is significantly less stiff than the original shank.

There are two ways to measure preload on a bolt; a torque wrench, and by measuring the angle the nut has turned. Of the two, the

latter is more accurate, as frictionplays a significant - and more importantly, indeterminate - role when using a torque wrench.

Torque = K preload diameter

K, the so-calledNut Factor, usually varies between 0.3 and 0.1, and is very sensitive to a number of factors, ranging from temperature

to thread condition, even to how fast the bolt is tightened.

Measuring the angle the nut has turned is simply measuring how much the bolt is stretching, equal to the pitch (distance between

threads) times the number of turns. Using this requires that the com

www.boltscience.com 10.04.13

Documents