HAND TOOL

any of the implements used by craftsmen in manual operations, such as chopping, chiseling, sawing, filing, or forging. Complementary tools, often needed as auxiliaries to shaping tools, include such implements as the hammer for nailing and the vise for holding. A craftsman may also use instruments that facilitate accurate measurements: the rule, divider, square, and others. Power toolsusually hand-held, motor-powered implements such as the electric drill or electric sawperform many of the old manual operations and as such may be considered hand tools. Additional reading The literature on hand tools is generally fragmented and without a single comprehensive treatment. Archaeological and anthropological information concerning the earliest tools may be found in: Chester S. Chard, Man in Prehistory, 2nd ed. (1974); Robert J. Braidwood, Prehistoric Men, 8th ed. (1975); Kenneth P. Oakley, Man the Tool-Maker, 6th ed. rev. (1972); and F. Clark Howell, Early Man (1973). Specific treatments are given in Franois Bordes, The Old Stone Age (1968; orginally published in French, 1961); and Jacques Bordaz, Tools of the Old and New Stone Age (1970). The rise of metal tools is found in Leslie Aitchison, A History of Metals, 2 vol. (1960); and Thomas A. Rickard, Man and Metals, 2 vol. (1932, reprinted in 1 vol. 1974). From Roman times onward, William L. Goodman, The History of Woodworking Tools (1964, reissued 1976), is definitive. R.A. Salaman, Dictionary of Tools Used in the Woodworking and Allied Trades, c. 17001970 (1975), is a comprehensive and very well-illustrated account. Henry C. Mercer, Ancient Carpenters' Tools: Together with Lumbermen's, Joiners', and Cabinet Makers' Tools in Use in the Eighteenth Century, 5th ed. (1975), should not be missed; and Peter C. Welsh, Woodworking Tools, 16001900 (1966), Paul B. Kebabian and William C. Lipke (eds.), Tools and Technologies: America's Wooden Age (1979), and Aldren A. Watson, Hand Tools: Their Ways and Workings (1982), include a wealth of illustrations. Charles Singer et al. (eds.), A History of Technology, 8 vol. (195484); and Maurice Daumas (ed.), Histoire gnrale des techniques, 5 vol. (196279), give wide but unconnected treatments. The first three volumes of Daumas's work cover the history of technology to the middle of the 19th century and have been published in English as A History of Technology & Invention: Progress Through the Ages, 3 vol. (196979). Illustrated by original drawings, Eric Sloane, A Museum of Early American Tools (1964); and Edwin Tunis, Colonial Craftsmen and the Beginnings of American Industry (1965), are highly informative because techniques and products of their period are shown in addition to tools. Relevant articles also may be found in serial publications such as Technikgeschichte (quarterly); Newcomen Society for the Study of the History of Engineering and Technology, Transactions (annual); and Technology and Culture (quarterly). The Early American Industries Association, Chronicle (quarterly), frequently contains articles on the history of hand tools. Many 19th-century books give detailed accounts of tools as well as of processes. Examples are Charles Holtzapffel and John Jacob Holtzapffel, Turning and Mechanical Manipulation, 5 vol. (184352). See also the article entitled Tool by Joseph G. Horner in the 11th edition of the Encyclopdia Britannica, vol. 27, pp. 1447, which contains a well-illustrated account of 19th-century developments in both hand and machine tools. Richard S. Hartenberg Joseph A. McGeough Later development of hand tools During the evolution of tools over more than 2,000,000 years, using as principal materials, successively, stone, bronze, and iron, humans developed a number of particular tools. Taken together, these specialized tools form an inverted pyramid resting upon the first general-purpose tool, the nearly formless chopper. With the discovery of metals and the support of numerous inventions allowing their exploitation, the first approximations to the modern forms of the basic tools of the craftsman established themselves, with the main thrust of further development directed at improving the cutting edges. The earliest tools were multipurpose; specialized tools were latecomers. A multipurpose tool, although able to do a number of things, does none of them as well as a tool designed or proportioned for one job and one material. The way in which a tool is hafted provides the primary distinction between the knife, ax, saw, and plane. An application or craft is best served by a further specialization or form within a category: the knives of the butcher, woodcarver, and barber reflect their particular tasks. When confronted with the unusual, a skilled craftsman develops a special tool to cope with the situation. In the early 19th century, for example, a joiner had dozens of planes in his kit to deal with the many moldings, rabbets, and jointings he had to produce before the day of machine-made stock and mill-planed lumber. Percussive tools Several tools involve a violent propulsion to deliver a telling blow. These have been named percussive tools, and their principal representatives are the ax and hammer. Under these two names are found an immense number of variations. The percussive group may also be called dynamic because of the swift motion and the large, short-term forces they develop. This means that mass and velocity and, hence, kinetic energy and momentum are factors related to the force generated or transmitted. The distribution of weight between the head and handle and the mechanical properties of the head (i.e., its suitability for a cutting edge or its lack of elasticity) must also be recognized in the design of a percussive tool. Obviously, these various influences were not formally considered during the agelong trial-and-error evolution of a now successful tool, but recognition of them aids in identifying the evolutionary stages of the tool. Percussive tools generally have handles that allow them to be swung; that is, their rapid motion endows them with kinetic energy. The attainable energy of a blow depends upon a number of factors, including the weight of the toolhead, the angle through which it is swung while gaining speed, the radius of the swing (handle length plus part or all of the arm length), and the muscle behind it all. There is a permissible energy level for a given task and tool, set by either the nature of the task or the material of the tool. Thus, a blacksmith flattening a one-inch lead bar needs a heavy, fairly long-handled hammer, whereas a light and short-handled hammer, used with wrist action, is appropriate for forging a small, soft gold wire. A hafted flint ax is an effective tool, but it may be destroyed if swung too hard or if twisted while in the cut. Bronze and steel axes can, and do, take longer handles than the stone ax and, being of tougher material, will not break under use that would fracture a stone head. The physics of percussive tools takes into consideration the centre of gravity and what is technically called the centre of percussioni.e., a unique point associated with a rotation, in this case the arc through which the tool is swung before delivering its blow and coming to rest. The tool's centre of gravity is readily found because it is the balance point, or location along the handle at which the tool can be picked up loosely and still remain in the horizontal position. The centre of percussion is the ideal point at which striking should occur on the toolhead to minimize the sting of the handle in the operator's hand as well as to deliver a blow with maximum force; this point is farther out than the centre of gravity and should be as close to the centre of the head as possible. This last condition is best met with a light handle and heavy toolhead, which places the centre of gravity close to the head and the centre of percussion in an optimum location in the cutting edge. It is apparent that the sheer weight of the head is of paramount importance in promoting a proper balance, or hang, to the tool. On this basis alone, the shift from stone axheads to metal was a step in the proper direction because metal heads of the same size as those of stone are about three times as heavy. With the heavier head, the centre of gravity of the hafted tool is closer to the head, and the centre of percussion is more likely to be properly located. With the mallet and chisel still other interrelations are involved. When working stone, a brittle material that responds to a sharp tool point by breaking into small chips, the sculptor strikes many light blows to remove material. As a consequence, mallets have short handles and the amplitude of swing is small, allowing a succession of rapid blows without undue fatigue. To provide energy and momentum, the mallet head is heavy. Being of wood, it does not rebound in the manner of a metal head but stays on the chisel, which transmits the blow to the cutting edge and focuses it into a small area of stone to be spalled off. The net effect of the proper combination of all elementsthe properties of wood, chisel, and stone, the weight of the head (perhaps even heightened by a lead-filled cavity), and the short handleis to waste the least energy. The wooden head is of course expendable, particularly if it is of a one-piece clublike construction, for it becomes badly battered from contact with the metal chisel. A more refined mallet consists of a separate head and handle, the head having a working face of end-grain wood. Working metal with a chisel requires that heavy blows be struck to enable the chisel to dig into the metal and lift out a chip. A steel hammer with a hardened face is used, and in this operation it is the soft end of the chisel that is battered and needs periodic dressing.