Threadlocking

HOW TO: THREADLOCKING

 

Every day we use products which contain numerous threaded fasteners. Screwed joints are among the most common form of a detachable yet secure fixing between two parts.

Although they come in various shapes and sizes, all threaded fasteners have the same purpose: to ensure a durable assembly.

This tutorial gives you more information about:

Threadlocking methods

Reasons for failure

Curing method of anaerobic productsM

Threadlocking: Additional Knowledge

Learn everything you need to know about the subject of threadlocking.

Application of tightening torque (unsecured nut & bolt)

  • Bolt is stretched like a spring
  • Required clamp load is reached
Threadlocking of fasteners and fittings - How nuts and bolts work.

Retention of clamp load:
Clamp load of unsecured nuts and bolts is only retained by bolt head friction or thread friction. To prevent loosening in case of e.g. vibration, an additional securing device is required.

Transverse shock test to show the performance of the different threadlocking methods.

Threadlocking of fasteners and fittings - Transverse shock test to show performance of threadlocking methods.

Relaxation

A change in bolt tension causes relaxation, leading to a reduced clamping force.

This effect is triggered by:

  • Settling ā€“ pressure-induced smoothing of the surface roughness.
  • Creeping ā€“ time-dependent yielding of substrates when loads exceed the compressive strength of the material e.g. when clamping gaskets.

If the elastic capacity of the assembly is inadequate, e.g. if bolts are too stiff or the wrong length-to-diameter ratio is selected, the loss of bolt tension cannot be compensated.

Threadlocking of fasteners and fittings - Relaxation as reason for failure.

Self-loosening

This is caused by dynamic loading, vibration or changes in temperature. Relative movements increase the risk of self-loosening.

Load changes lead to short-term frictionless situations where the bolt unwinds from the nut. Ultimately these movements result in the loosening of the threaded assembly. Self-loosening can only be avoided by using the appropriate threadlocking methods.

Threadlocking of fasteners and fittings - Self-loosening as reason for failure.

Thermal expansion differentials

Dissimilar metals have different thermal expansion coefficients. This may result in loss in bolt tension and reduction in clamp force.

Threadlocking of fasteners and fittings - Thermal expansion differentials as reason for failure.

Corrosion

Water ingress can create corrosion in the threads. This may result in loss of bolt tension, with disassembly often impeded

Threadlocking of fasteners and fittings - Corrosion as reason for failure.