文档介绍：Screwdriver 螺丝刀? It would be very difficult to find a Chinese household that did not have at least one screwdriver. Perhaps the most ubiquitous of hand tools, the screwdriver has a long genealogy, the result of plicated manufacturing process. Archimedes is considered to have invented the screw in the third century ., though his invention was designed to transfer motion (as in the continuous worm of a worm and gear assembly) rather than to fasten things together. ? By the first century ., large wooden screws were used in presses for producing wine and olive oil, and were turned with spikes stuck into or through a handle that resembled a modern corkscrew used for opening wine bottles, although larger. These were made of wood with a flat rather than a pointed end, and a container to hold the material being pressed. ? Metal screws and nuts seem to have been used as fasteners in the fifteenth century, although the heads of these screws were turned with a wrench and not a screwdriver — the screw heads were either square or hexagonal. Screws with slots in their heads were found in armor in the following century, although the design of the tool used to work the screws, the screwdriver, is unknown. ? The modern screwdriver descends directly from a flat-bladed bit used in a carpenter's brace circa 1750. Woodworkers were using hand screwdrivers in the early 1800s, and they became mon after 1850, when machines made the automatic production of screws possible. These early screwdrivers were flat throughout the length of their shaft; the current design of a rounded bar that is flattened or shaped only at the working end makes the tool much stronger and takes advantage of the round wire used in its manufacture. The oldest and mon type of screwdriver is the slotted screwdriver, which fits a screw with a single slot in the head. There are perhaps thirty different types of screwdrivers available today in a variety of sizes, all with different purposes and all designe