The Inscrutable Screw

screwThe humble screw has been the downfall of many a DIY attempt and the saviour of many a building project. A simple shaft – usually metal – has a thread running down its length to allow it to fix one item or surface to another. For every type of screw there needs to be a tool designed to fasten or unfasten it.

A Brief History of the Screw

According to the website Inscrutables, there is evidence that screws were being used as early as the first century AD, with examples of wooden screw mechanisms in olive and wine presses. Metal screws appeared during the 15th century but it was not until the 18th century that lathes were developed that were capable of mass-producing the threaded metal screw.

Types of Screw
The most familiar type of screw is the flat head, or ‘cut slot drive’ as it is also known. Although this is extremely popular, it is actually slowly going out of fashion thanks to its eventual loss of integrity as the metal slot becomes damaged by repeated use.

The ‘cross head’ screw is similar to the flat head, but with two slots forming an X shape. This gives it a slight advantage over the flat head screw as it makes it less prone to damage from the screwdriver.

The ‘lotus head drive’ is a specialised type of cross head screw devised in Taiwan. Cheaper to manufacture than the cross head screw, and designed to be more robust, this is most commonly found in toys and light fittings.

The ‘square head’ has a recessed square that gives the screwdriver greater purchase and allows it to be place in position while mounted on the driver. There is similar type of screw with a slightly different recessed pattern known as the Robertson screw.

The ‘recessed cross drive screw’ is more commonly known as the Phillips screw, named after its inventor, Henry F Phillips, in the early 20th century. The design of the recessed head means that the screw cannot be tightened too far as the screwdriver loses purchase at that point.

The ‘posidriv’ is a variant of the Phillips screw, along with a slightly superior version known as the ‘supadriv’. Phillips also specialise in a wide range of recessed screw heads designed for the manufacturing and aerospace industries.

For specialised applications where security is of concern, there is the ‘tamper-proof security screw’. These screws are often used by manufacturers who do not wish the public to open a particular mechanism, or where tampering is of concern.

You will find a huge array of different types of screw online, far surpassing anything you could find in a hardware store. Large online wholesalers have extensive stocks on offer. For example, you can find anything from roofing bolts to sturdy security screws from RS Components and similar online retailers.

In the future, we can expect to see a steady rise in the use of the Uni-Screw, which plans to do away with the many different screwdrivers in our toolkits by developing this recessed hexagonal design and introducing it across the DIY and building markets.


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