A company called Yamaoka Seisakusho designs and manufactures metal dies and devices used to make semiconductors. The dies have complex shapes with many different lengths and curves to match an outline on a circuit board, on which semiconductors are mounted. They are made to exact specifications, a process which requires real precision.

The company's precision technology depends partly on human hands. During the final process, an operator peers through a microscope at the die surfaces, polishing them carefully with a diamond abrasive tool head that is vibrated by supersonic waves. Human hands are used because only they are precise enough to do the job properly.

Yamamoto Nobuyuki, one of the company's expert die polishers, told me, "This job requires a lot of concentration, and sometimes I have to hold my breath. The die has to be polished until surface irregularities measure less than one-thousandth of a millimeter."

The dies are made to the exact and varied shapes demanded by customers. The operator uses a number of polishing tools, choosing the best one for the shape of each metal part. Not all of the tools are made of metal—I was surprised to learn that even bamboo skewers and wooden toothpicks are used! After the die is polished with a metal tool, some small scratches remain, which can be removed more precisely with a soft, non-metal material, like bamboo or willow. Yamamoto says workers doing this type of work before him discovered how to use these unusual materials and tools, and he still follows their techniques.

Technicians can feel irregularities of only a few thousandths of a millimeter just by running their fingers across the surface. Human hands keep playing a vital role in the development of high-tech industries.