Human beings have been using screws since the first Century CE, when wooden screws were used for pressing oil, wine and clothing. Before that, screw shaped designs were used in the movement of water and grains – a technique made famous by the Greek inventor and philosopher Archimedes. Screws are defined by their thread: a spiral of material that enables them to grip on to materials effectively. Metal screws first came into use during the 15th Century, a time when the construction field experienced a huge leap in the West. Today there are many different kinds of screw available. Here is an extremely brief guide to some of the most important varieties.
Wood is one of the material most associated with the many different kinds of screws. Not all screws, however, are suitable for attaching bits of wood together. In order to correctly bond wood, screws need to have a semi threaded shank. Semi threaded shanks allow for a tighter grip in softer materials such as wood. This kind of screw is immensely popular with DIY enthusiasts as it is pretty much perfect for most basic applications. They are not very useful in specialist applications or when attaching wood to other materials with different properties such as metal.
Pocket Hole Screws
In many carpentry applications, pocket holes are drilled into sections of wood before a screw is inserted. Pocket hole screws are designed to fit snugly into these predrilled holes without ‘stripping’ the wood and changing the size of the hole. They are designed for quick insertion with a drill and have very flat heads. They are somewhat difficult to remove once they have been installed due to this flatness. Some carpenters use pocket hole screws in order to obscure the screw head into the wood for a more aesthetically pleasing finish.
Deck/ Outdoor Screws
Deck screws are made specifically for use in outdoor applications. They are designed to be especially resistant to corrosion. This is usually achieved through material choice – stainless steel is the most common material for making deck screws. Corrosion of a screw inside wood can seriously compromise the structure of a carpentry project and eventually cause warping or complete detachment.
Masonry screws have a broad thread and are perfect for attaching wood to concrete and stone. In order to successfully use masonry nails a pilot hole must be drilled into the materials beforehand. Due to the hardness of stone and concrete any attempt to insert a screw without a pilot hole is likely to result in a failure to correctly align the screw without damaging the material.
Sheet Metal Screws
On the other end of the scale entirely, sheet metal screws have an incredibly fine thread. They also have a very sharp tip. These features help the screw penetrate hard metal and cling to even the thinnest section of material. Sheet metal screws are wholly inadequate for use in wood but are a must-have for thin strips of sheet metal.