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Chinese Abacus

By Tom Parker

Sometimes it costs more to buy it than to make it from the money itself.

Photograph by Tom Parker

$17.95

Wood-frame Chinese abacus bought online.

The Chinese abacus, or counting frame, is an ancient calculator using beads on rods for both decimal and hexadecimal computation. In many parts of the world, schoolchildren still use these ingenious devices to do large-scale addition, subtraction, multiplication, division, and even square-and cube-root operations at astounding speeds.

I made mine in the “Adirondack porch furniture” style, with a frame of dried chokecherry twigs. Since twigs aren’t perfectly straight, I clamped each one in a jig so I could drill orderly and parallel holes using a drill press. First I drilled flat-bottomed holes for the joints of the frame, using Forstner bits. For the rods, I drilled carefully spaced sets of holes, sized so that I could press-fit coat-hanger wire. If you size your holes right, the frame and rods just snap together.

$0.93

Chinese abacus made of pennies, twigs, and coat-hanger wire.

The traditional Chinese abacus has seven beads on each rod, two above and five below. These are usually made of wood, glass, or stone, rounded for easy manipulation. I wanted to make my beads out of pennies, but flat disks would be hard to separate and slide with your fingers. So I chose pre-1982 pennies, which are 95% copper and easy to deform. (The newer zinc pennies tend to snap when bent.)

I center-drilled each penny first. Then I fashioned a crude deforming tool using a bench vise. To one jaw of the vise, I glued an old cylindrical bushing the same diameter as a penny. I sawed off a ″ hex bolt, filed it to a smoothly rounded stub, and glued it to the other jaw, just opposite the bushing. This gave me a “tooth” I could use to deform each penny with a simple clamping operation.