A jeweler’s screwdriver is a type of very small screwdriver. These specialty tools are primarily used on high-precision or very small systems like watches or eyeglasses. These screwdrivers are always mechanical, meaning they are hand-powered rather than electric. In addition, a jeweler's screwdriver will have a flat head and no flaring on the tip. In most cases, a jeweler’s screwdriver has a cap on the top of the handle that allows the shaft to turn freely while still being supported.
The purpose of a screwdriver is to transfer energy into a screw. Screws are one of the first human-made complex tools. A screw has a disproportionately high surface area which allows it to magnify friction and inertia far beyond what would normally be available for an item its size. Due to the nature of the screw, humans can’t use it directly and need a tool to interact with it.
A screwdriver is made of three parts: the handle, the shaft and the tip or blade. The shaft is generally the most straightforward part; it is simply a shaft of metal that connects the handle and the blade. Even in a very complex screwdriver, the complexity is before or after the shaft. The shaft is almost always solid to prevent structural breaks when the tool is in use.
The handle of a screwdriver can be as simple as the shaft or much more complex. A simple handle is made of wood or plastic that is affixed to the shaft. The material is often textured in some way to assist humans in gripping it. Complex handles may have a ratcheting or electrical system. Ratchets allow the shaft to turn in one direction freely, removing the need to remove the driver from the screw. Electrical systems usually have a motor which rotates the shaft and turns electricity into torque rather than human muscle.
The blade, or tip, is the part that interacts with the screw. A keystone design will flare out as the shaft transitions into the blade, while a cabinet has no flare. When the screwdriver has a flat end, it is typically called a blade. When the end is shaped, like a star or hexagon head, it is usually called a tip.
The most common type of jeweler’s screwdriver is a flat cabinet-style blade. These tools are much smaller than a typical screwdriver and have a specialized handle to assist in their use. The top of the handle on a jeweler’s screwdriver has a rotating disk that rests in the palm of the user’s hand. This allows the user to turn the screwdriver with the tips of his fingers without removing the blade from the screw.