A mechanical fastener is a device that is used to mechanically join (or fasten or affixes) two or more objects together. 

In general, fasteners are used to create non-permanent joints; that is, joints that can be removed or dismantled without damaging the joining components.


Bolts are mechanical fasteners used for the assembly of two non threaded components, with the aid of washer and nut.

A bolt has a head on one end and threads on the other end.

When the objects are fastened, the bolt holds the objects together, and washer and nut fasten from the other end that holds it firmly.

  • Bolted joint is a combination of the nut applying an axial clamping force and the plain non threaded length (known as shrank) of the bolt pinning the joint against sideways shear forces.
  • The non threaded grip length should be chosen carefully, to be around the same length as the thickness of the material and washers through which the bolt passes.
  • An overly long non threaded length prevents the nut from being tightened down correctly.
  • An insufficient non threaded length results in the threads extending into the hole, and places the shear load onto the threads, which may cause wear on the hole.
  • No more than two turns of the thread should be within the hole.

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