A linkage of parallelograms that copied drawings, coins and even census cards
Trace a drawing with one arm of a pantograph and a pen on another arm redraws it, the same size, bigger or smaller. The trick relies on nothing but hinged parallelograms. That simple linkage went on to shrink sculptures, mill machine parts, engrave coins and punch the cards for the 1890 US census.
The name joins Greek roots for all and write, since the device began as a copier of writing. Hero of Alexandria described it in antiquity. In 1603 Christoph Scheiner used one to copy and rescale diagrams, though he waited until 1631 to publish a book on it. Moving the joints between the pointer arm and the drawing arm changes the scale. In 1821 William Wallace improved on the design with the eidograph, which moves the fixed pivot to the middle of a slim parallelogram.
Sculptors adopted a three-dimensional version: a long boom anchored at one end with two needles set along it, their spacing fixing the ratio. James Watt, better known for steam engines, devised it, and Benjamin Cheverton perfected it in 1836 with a spinning cutter that carved small replicas of famous statues. A related machine still reduces large relief designs down to coin size.
Factories leaned on the idea before computers took over. Without numerical control, a milling cutter could only be guided by a steady hand or by tracing a template, and mounting it on a pantograph let machinists cut duplicate parts at different scales. Engraving machines worked the same way, following lettered plates at reductions of up to 50 to 1. Linn Boyd Benton built one for type design that could not just resize letters but condense, stretch and slant them, the same geometric operations digital typography relies on today.
Stranger applications abound. Herman Hollerith's keyboard punch for the 1890 census was nicknamed the Pantograph Punch, and in 1886 Eduard Selling patented a prize-winning calculator built on the principle. Quilters still trace paper patterns called pantographs, and Richard Feynman borrowed the image to imagine scaling tools down to the nanometre.
Source: Pantograph
