Simple hand tools, which cut or pound or assemble, may now be sold with attached metal or plastic handles, but their basic designs and operations have not changed over time. The plane and the file smooth down metal or wood surfaces. Drills and saws are now primarily electric, to save time and energy. Hammers come in all sizes, from the rock-breaking sledgehammer to the tiny jeweler's model, which is used to stamp insignias into soft metals like sterling or gold. Screwdrivers attach screws and wrenches tighten nuts and bolts together in areas where larger tools would not reach as easily. Measuring tools are also included under the category of hand tools, since they include tape or folding measures which may be carried on a tool belt. Squares and levels now measure inclines and angles with liquid crystal digital displays, but they otherwise look and feel like their old-fashioned counterparts.
Current research and development applies computeraided design (CAD) programs to simulate models as if under stress of actual use, in order to test possible innovations without the expense of building real prototypes. Lightweight alloys, plastics, and engineered woods are used to improve versatility and convenience. Poisonous heavy metals are being replaced with safer plating materials, and nickel-cadmium batteries may soon be replaced with rechargeable units that are easier to recycle.
Schick, Kathy D., and Nicholas Toth. Making Silent Stones Speak: Human Evolution and the Dawn of Technology. New York: Simon & Schuster, 1993.
"How Designs Evolve." Technology Review (January 1993). "Iceman's Stone Age Outfit Offers Clues to a Culture." New York Times (June 21, 1994): B7.
"Recreating Stone Tools to Learn Makers' Ways." New York Times (December 20, 1994): B5.
"The Technology of Tools." Popular Science (September 1993). "Tool Training at the Chimp Academy." New Scientist (May 11, 1991).