Anti-seize is a lubricant designed to limit the friction on fasteners during installation and reduce the chance of thread galling.
Threadlocker is a paste that is applied to fastener threading before installation. Once installed the paste cures and holds the threads in place.
Tolerance is the accepted amount of variation from fastener to fastener that is allowed while still being considered the same size.
Shear strength is the amount of force a fastener can handle from its side without shearing.
Tensile strenght is the maximum load in tension a fastener can handle before or at breaking point.
When a fastener is exposed to multiple elements (heat, removal and reapplying pressure and other stress factors), a fastener will change shape and return to its original form. Fatigue strength refers to the maximum amount of stress it can handle for a number of cycles and still return to normal. Once a fastener exceeds its fatigue strength it is very likely to develop faults.
Galling can be prevented by making sure an quality anti-seize lubrication is applied to the threads of a fastener prior to installation.
Installation torque is the highest torque needed to install a fastener before axial loading occurs.
Breakloose torque is the initial amount of torque required to begin decompressing a fastener assembly
An axail load is the amount of pulling or stretching force placed on the axis of rotation. One way to think of axial load is when attatching two pieces of wood together with a nut and bolt. Once the nut begins to firmly press against the wood, it begings to exert compression force. As the two pieces of wood struggle to maintain their original shape, force is exerted against the nut and bolt head by the wood. The force exerted against the nut and bolt are the axial load. This load can be increased by adding additional weight to the wood itself.
Tensile load is maximum load that can be applied to a fastener before its breaking point. This force is tested by the installation materials pushing against the head and nut of the bolt.
Elongation is the stretching of a fastener from head to tip which causes the bolt to warp. It is caused by too much torque applied to a bolt or too much pressure being applied.
Torsional strength is the amount of torque a fastener can handle before it breaks.
Yield strength is the amount of force that can be applied to a fastener before it “yields” and begins to warp.
Hardness refers to a materials ability to cause damage to another material without causing damage to itself. Example: It is possible to scratch your phone screen with your keys without damaging the keys. This is because your keys are harder than the glass screen.
Galling is the fusion that occurs when metal is moving very fast against metal with friction and pressure. It causes the two pieces to weld together on the surface level which is known as galling. Stainless steel, aluminum, titanium and hot dip galvanized fasteners are all prone to galling.
Corrosion is the breakdown of a material due to contact with either a corrosive chemical or another material it reacts with. The latter is known as galvanic corrosion.
Prevailing torque is the measure pressure it takes to cause frictional resistance to rotation.
The amount of torque required to start rotation between a fastener and its locking mechanism (such as a nut) when no axial load is present.
Seating torque is the torque that needs to be applied to create a compressive load under the head of the fastener.