Fasteners A Brief Overview,Choosing a suitable fastener

We probably use some form of fasteners nearly every day in some form or another.The screw thread found on modern stainless steel nuts and bolts can actually be dated back to Archimedes in the 3rd century “The Archimedes Thread”, yet in its modern form it only really came of age in the early 1,800’s when in 1840 Frank Whitworth proposed a set of common sizes of screw thread spacing and pitches.

This resulted in the “Whitworth” threads, which whilst now having been overcome by metric sizes, are still in use today in engineering workshops.

suitable fastener

Fasteners normally come with an internal or an external thread.


An external thread would be that found on the outside of a bolt or screw. An internal thread would be that found on the inside of a nut.

A screw is defined as a fastener that can be tightened simply by applying torque to its head. Where as a bolt cannot be tightened simply by putting torque on its head, it needs a nut on the other side of it in order to be tightened up.

Yet there is a grey area, and that is machine screws. 

Machine screws look identical to bolts yet can be self tightening like a screw when they are inserted into tapped holes.

Screw thread fasteners come in a wide range of sizes and materials, from nuts and bolts that are strong enough to hold bridges together, through to small stainless steel nuts and bolts used in the assembly of motorbikes or machine parts.

Choosing a suitable fastener needs to be done with some care. 

For example in anything that is exposed to the weather on a regular basis then you should always choose stainless steel fasteners, as steel, whilst cheaper will rust very quickly when left exposed to the elements. In high load applications you may well buy fasteners that have been tested and certified to a particular breaking strength.

A great deal of care has to be taken such that you do not choose the wrong fastener material, otherwise electrolytic action may occur causing corrosion.

Fasteners also fall under two key definitions, and that is ones with a non-tapered shank, and ones with a tapered shank.

Fasteners with a tapered shank are ones such as screws that are self tapping. Ones with a non-tapered shank are those such as normal bolts that are not self tightening in the way that a screw is.

This is a brief overview of what fasteners are.

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