A screw is a type of fastener that is used to attach two different surfaces like a drywall and a metal sheet. Screws have a head on one end and threads on its tapering end. The threads are designed so that a screw can be fastened into a groove. This prevents the screw from being pulled out easily.
Screws have been used since ancient times. The first screws were wood screws, named so because they were primarily used on wood. These were often blunt in one end and lacked the precision of screws which came later. Machine screws, including brass machine screws, are built by machining.
History
The use of metal fasteners to hold together wooden furnishing is almost as old as the use of wood for making implements and furniture. The use of wooden and metal can be found in many ancient civilisations, although these are not strictly speaking (as per their construction) actually screws. These were more like fasteners.
Screws were mostly used in carpentry and smithing. Their use was to build furniture, weapons and implements. Threaded screws were by no means uncommon, but metal screws as we know them today were not as widespread in the medieval world. Metal tools actually became more widespread after machine made their mass-production possible in the later half of the 18th century.
This was also a period of remarkable scientific inventions and entrepreneurial thrust. The world was changing as a machines first started to change the way we saw manufacturing, infrastructure and every other facet of life. It would not be wrong to say that screws, as simple implements that hold everything together, were the unsung and unrecognised linchpin of the time.
Manufacturing
Whether a screw is made manually or by machine, there are three main steps in its manufacturing process. This essential manufacturing process applies to any material used in screw making, whether steel or brass machine screws.
The three steps in screw manufacturing are heading, thread rolling and coating. Thin screws are made from wires and the thicker ones are made from round bar stock. To make the screw, this raw material is cut into the desired size. At this stage it is known as blank.
The blanks then goes through a cold working process or cold headed as it is more commonly known. We start with heading where the head of the screw is made. The desired features are pressed into the screw head.
The pattern is important because it the head will be classified on the basis of this. It determines the drive type of the screw (or the type of screwdriver it will require). The shape pf the head is also equally important. It can be flat, rounded or polygonal. This again influences the drive of the screw.
The heading of the screw is also important in the manufacturing process because it dictates the efficiency in production. Some screw heads require less effort and less waste. A simple flat head will require a flat dies, some shapes may require two heading processes. Slotted heads will also need slotting machine.
The screw is still a blank. It requires polish and proper threading of the shank. This is done by thread rolling or cutting. There could be further polishing to removing any waste metal and smoothen the surfaces. Even a small irregularity will hamper its functioning.
Some screws may also need coating. This is done to add to the properties of the screw making material. For instance, plastic coating can be added for electrical insulation. Similarly, zinc plating is often applied for resisting corrosion.
Material
Steel is the most common metal in screw making. However, for special projects we still need brass machine screws. Made of brass, these screws have the properties that we get from brass, mainly better ductility and corrosion resistance.
Brass screws are mainly used where we need a high resistance to corrosion, such as in high humidity. Brass screws last longer without rusting than the more commonly used steel. Alloys of brass are even used in naval applications.
Brass screws are also used when we need aesthetics, such as in carpentry. The dull golden finish of brass is a high advantage in the overall finish of the product.
