Fastener

fastener banner 3A fastener, abbreviated as FSTNR, is hardware that mechanically joins two or more objects together.

 

 

 

 

 

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fastener Types

  • Permanent  -  These parts will never be disassembled like rivets and welding.
  • Removable  -  These parts can be disconnected without damaging the fastener like nut and bolt.
  • Semi-permanent  -  These parts can be disconnected, but some damage can occurs to the fastener like a cotter pin.

 

fastener standards

ASME Standards

  • ASME B1.20.1 - Pipe Threads, General Purpose, Inch
  • ASME B1.20.3 - Dryseal Pipe Threads, Inch
  • ASME B18.12 - Glossary of Terms for Mechanical Fasteners
  • ASME B18.18 - Quality Assurance for Fasteners

 

Fastener Glossary

A

  • Aerotight nut  -  A torque prevailing nut for all metal construction. The nut is slotted in two places which, after the nut has been tapped, are bent slightly inwards and downwards.  When the nut is screwed onto the bolt thread the two slotted parts are forced back to their original position.  Their stiffness causes the nut threads to bind onto the bolt threads and thus provides a prevailing torque. 
  • Allowance  -  The clearance is between internal or external threads.  Not all classes of threads have an allowances.  For metric threads the allowance is called the fundamental deviation.
  • Alloy steel  -  A steel that one or more elements (other than carbon) have been added.
  • Anchor  -  Types of anchores.
  • Anchor bolt  -  Anchor bolt is a threaded item used to secure an embed fastener into concrete, structural supports, walls, etc..
  • Angle controlled tightening  -  A 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 is further tightened by giving the nut an additional measured rotation.
  • Anti-friction coating  -  These coatings are dry lubricants consisting of suspensions of solid lubricants, such as graphite, PTFE or molydbenum disulphide of small particle size in a binder.
  • Anti-seize compound  -  An anti-seize compound is used on the threads of fasteners in some applications.  The purpose of the compound depends upon the application.
  • Annealing  -  A process of heat treatment that changes the properties of metals.
  • Autolock nut  -  A torque prevailing nut.

B

  • Band hanger  -  A pipe attachment providing vertical adjustment, normally of a formed steel strap.
  • Basic thread profile  -  This is the theoretical profile of external and internal threads with no manufacturing tolerance applied.
  • Beam clamp  -  A clamp that is used to attach rod hangers to beams by clamping onto the beam flange.
  • Black bolts and nuts  -  The word black refers to the comparatively wider tolerances employed and not necessarily to the colour of the surface finish of the fastener.
  • Bolt  -  A fastener with a head and threaded on one end only.
  • Bolt head  -  Formed by heating the end of a round piece of steel round bar then forged in to a head shape.
  • Bolt grip length  -  Total distance between the underside of the nut to the bearing face of the bolt head, includes washer and gasket thickness etc.
  • Bolt normal length  -  The distance from the bottom of the bolt head to the end of the bolt.
  • Bolt stud  -  A bolt stud is threaded on both ends or the full length.
  • Bolt torque  -  Torque, also called moment of force, is a rotational moment. It is a measure of how much twisting is applied to tighten (turn) the nut on a bolt.
  • British Sandard 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 in BS 84: 1956.
  • BSW  -  British Standard Whitworth
  • Bump thread  -  It is a modified thread profile.  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.

C

  • Center beam clamp  -  A jaw type beam clamp use with I-beams and wide flange beams which provides a centered beam connection.
  • Clevis hanger  -  A fastener that provides vertical adjustment, consisting of a clevis type top bolted to a formed steel bottom strap
  • Cold forming  -  A material is placed between two dies and compressed into a shape.
  • Compression spring  -  A compression spring is a open-coil helical springs wound to resist the compression force along the wind axis.  The spring will always resist and pushing back the compression force to its origional length.
  • Compression strength  -  Compression strength is the ability of a material to withstand applied loads without failure.
  • Corrosion resistant  -  The ability to resist corrosin under certain conditions.
  • Cut thread  -  A threading method produced by removing material from the surface with a form cutting tool.

D

  • Dacromet  -  A high performance surface coating that can be applied to fasteners.  The coating consists of zinc flakes that are oven heated onto the metal surface.
  • Decompression point  -  The point at which there is zero pressure at the joint interface as a result of forces applied to the joint. 
  • Deformation  -  Is measured by how much an object is deformed from its origional dimensions.
  • Direct tension indicator  -  Projections on the face of the washer that deform under pressure as the bolt is put under tension. An indication of the tension in the bolt can be made by measuring the gap between the washer face and the nut or bolt head. The smaller the gap - the greater the tension in the bolt.

E

  • Effective diameter  -  See pitch diameter.
  • Elastic modulus  -  The ratio of the stress applied to a body or substance to the resulting strain within the elastic limits.
  • External thread  -  A screw thread that is formed on the external cylinder.  Also called male thread.

F

  • Fastener length  -  Measured from the top of the head to the bottom of the threads.
  • Force  -  The push or pull of an object resulting in a change from rest or motion.
  • Forging  -  The process of forming raw steel by displacement under force into specified shapes.
  • Friction  -  The mechanical resistance to the relative movement of two surfaces.

G

  • Galling  -  A severe wear which occurs during the pressure of sliding contact, one surface relative to another.

H

  • Hex head bolt  - A bolt with six sided head.
  • Hex head cap screw  -  A hex head screw with a flat and washer faced bearing surface under the head.
  • Hooke's law  -  States that the amount of spring force, compressed or stretched, is proportional applied to the spring deformation.  The minus sign shows that the force is in the opposite direction of the force that is compressed of stretched.

I

  • IFI  -  Industrial Fasteners Institute
  • Internal thread  -  A screw thread that is formed inside a hole.  Also called female thread.

J

K

L

  • Leaf spring stiffness  -  Leaf springs are spring made of thin strips of metal (could be a single strip) stacked in layers to asorbe the vibration.  They are normally used on suspension systems for wheeled vehicles or trailers.

  • Left hand thread  -  A screw head that rotates counterclockwise direction.  Not as widely used as righthanded threads.
  • Lock nut  -  Resists loosening under vibration and torque.

M

  • Major diameter  -  The largest diameter of a screw thread.
  • Minor diameter  -  The smaller diameter of a screw thread.
  • Moment arm  - The distance from the pivot point to the point where the force occurs.

N

  • Nail  -  Types of nails.
  • National pipe thread  -  NPT pipe threades or American Standard Taper Pipe Threads are used frequently in the oil and gas industry.
  • Nominal diameter  -  The external size diameter designated of pipe or threads.
  • Nut  -  Types of nuts.
  • Nut runner  -  A torque control fastener tightening tool that is usually powered by compressed air.

O

P

  • Pitch diameter  -  See thread pitch diameter.
  • Preload  -  The tension created in a fastener when first tightened but reduces after a period of time.
  • Pressure  -  The force exerted perpendicular to the surface of an object and is expressed as force per unit area.
  • Proof load  -  The amount of stress that the fastener can withstand without experiencing deformation.

Q

  • Quenching  -  A process of quickly cooling an elevated temperature.

R

  • Right hand thread  -  A screw head that rotates clockwise.

S

  • Shank diameter  -  The smooth part of the bolt above the threads.
  • Shear stress  -  Tends to deform the material by breaking rather than stretching without changing the volume by restraining the object.
  • Spring diameter  -  Distance from center of wire diameter to center of wire diameter.
  • Spring displacement  -  Spring deflection or travel distance, is the compression (a repulsive force) or stretching (an attractive force) of a spring.
  • Spring index  -  The ratio between the spring and wire diameter for a helical spring.
  • Spring load  -  The load applied to a spring to compress the length.
  • Spring number of active coils  -  Active coils are the open wound coils exerting energy while under a load of compression, extending, or deflection.  A coil is formed when it is wound one complete 360 degree helix starting with the second coil and count to the second coil on the other end.
  • Spring tension  -  How much load/force is initially exerted on the spring to expand it.
  • Strain  -  The deformation, stretched or compressed, of a material compared to its original length.
  • Stress  -  The force per unit area of cross-section.

T

  • Tap bolt  -  A bolt that is threaded to the botom of the head.
  • Tensile strength  -  The maximum stress a material can resist before it starts to elongate.
  • Tension strength  -  The capacity of a material to resist a force tending to stretch it.
  • Thread angle  -  The angle between the thread flanks.
  • Thread axis  -  The imaginary distance equally between the major and minor diameters.
  • Thread count  -  The number of threads per inch (TPI), used for US threads.
  • Thread crest  -  The peak of a thread at the major diameter.
  • Thread flank  -  The side of a thread between the major and minor diameters.
  • Thread height  -  The perpendicular distance between the major and minor diameters.
  • Thread length  -  Length of the cylinder that is threaded.
  • Thread pitch  -  The distance measured parallel between the crests of one thread to the next thread.
  • Thread pitch diameter  -  The imaginary diameter equal distance between the major and minor diameters.  Also called effective diameter.
  • Thread root  -  The bottom of the thread.
  • Torque  -  A rotational moment.

U

  • UNC  -  United National Course
  • UNEF  -  United National Extra Fine
  • UNF  -  United National Fine
  • UNR  -  United National (UN)

V

W

  • Wahl correction factor  -  A method to find out the effect of direct sheat and change in coil curvature in a spring.
  • Washer  -  Types of washers.

X

Y

  • Yield point  -  The point where an elastic material is permanent change in length with no extra load force.

Z

 

Display #
Title
Anchor
Angle Controlled Tightening
Anti-friction Coating
Anti-seize Compound
Bolt