History and Development
Screw threads have been in existence for thousands of years, but these were of wood and typically used in the construction of presses for oil, wine and clothes.
The first evidence of metal screws and nuts dates to the 15th century, where they were used to hold together parts of a suit of armour. Not surprisingly it's at about this time that the first evidence of screwdrivers was discovered, although they were called 'turnscrews' then.
Early screws were slotted with a hacksaw and the threads filed by hand. It wasn't until the late 1700s that the first screw cutting lathes began to make mass production of threaded screws viable.
The Industrial Revolution drove the proliferation of different screw driving systems since mass production demanded a better productivity than could be achieved with slotted screws.
In 1908 screws with a square hole in the head were invented by Canadian P L Robertson, these rapidly became a North American standard, but since the amount of turning force (torque) applied to the screws could not at that time be effectively controlled, there was always a risk of over-tightening and breaking the screw or stripping the threads.
This lead to the development of screws with heads specifically designed to prevent over-tightening. These screws have a cross shaped slot in the head designed to make the screwdriver turn out (or cam out) of the slot rather than allow over-tightening. There are two main types of cross head screws: Phillips and PoziDriv® (also known as SupaDriv®) which we will come to in a minute.
With the development of controlled torque screw driving devices and in an attempt to introduce some level of security, other screw drives such as Torx® and hexagon (Allen®) have been developed and are used particularly in Automotive and Electrical appliance manufacture world wide.
OK, so that's how they developed, but what do all these different screw drivers look like? Well, we'll come to that shortly but first let's get some terminology under our belts.