Screws and Screwdrivers
Screwdrivers are used to drive screws into a variety of materials. Turning the screw clockwise(right) drives the screw in, turning the screw counterclockwise(left) removes the screw. The common saying is, "lefty loosey, righty tighty".There are many different types of screws and screwdrivers.
Common Screw and Screwdriver Types
Flathead/Slot:
The slot screw drive has a single slot in the fastener head and is driven by a "common blade" or flat-bladed screwdriver. It was the first type of screw drive to be developed, and for centuries it was the simplest and cheapest to make. The slotted screw is common in simple woodworking applications, but is not often seen in applications where a power tool would be used because a power driver tends to slip out of the head, potentially damaging the surrounding material. The tool used to drive a slot is called a common blade, standard, flat-blade, slot-head, flat-tip or "flat-head/flathead" screwdriver.
The Phillips screw design was developed as a direct solution to a number of problems with slotted screws: easy cam out (the screwdriver slipping out of the screw), precise alignment required to avoid cam out and damage, and difficulty of driving with powered tools.
Philips:
Hex:
For hex screws a hex key, also known as an Allen wrench is used. Somewhat different than a standard screwdriver design, Allen wrenches typically come in sets with different sizes of keys included.
The Torx screw uses a star-shaped recess in the fastener with six rounded points. It was designed to permit increased torque transfer from the driver to the bit compared to other drive systems. Torx is very popular in the automotive and electronics industries because of resistance to cam out and extended bit life, as well as reduced operator fatigue by minimizing the need to bear down on the drive tool to prevent cam out.
Torx:
