Jig borer

The jig borer is a type of machine tool invented at the end of World War I to make possible the quick-yet-very-precise location of hole centers. It was invented independently in the United States and Switzerland. It can be viewed as a specialized species of boring mill or milling machine that provided tool and die makers with a higher degree of positioning precision (repeatability) and accuracy than those general machines had previously provided.

History

Before the jig borer was developed, hole center location had been accomplished either with layout (either quickly-but-imprecisely or painstakingly-and-precisely) or with drill jigs (themselves made with painstaking-and-precise layout). The jig borer was invented to expedite the making of drill jigs, but it helped to eliminate the need for drill jigs entirely by making quick precision directly available for the parts that the jigs would have been created for. The revolutionary underlying principle was that advances in machine tool control that expedited the making of jigs were fundamentally a way to expedite the cutting process itself, for which the jig was just a means to an end. Thus the jig borer's development helped advance machine tool technology toward later NC and CNC development. The jig borer was a logical extension of manual machine tool technology that began to incorporate some then-novel concepts that would become routine with NC and CNC control, such as:

• coordinate dimensioning (dimensioning of all locations on the part from a single reference point);
• working routinely in "tenths" (ten-thousandths of an inch, 0.0001") as a fast, everyday machine capability (whereas it formerly was the exclusive domain of special, time-consuming, craftsman-dependent manual skills); and
• circumventing jigs altogether.

Franklin D. Jones, in his textbook Machine Shop Training Course (5th ed), recorded insightfully:

"In many cases, a jig borer is a 'jig eliminator.' In other words, such a machine may be used instead of a jig either when the quantity of work is not large enough to warrant making a jig or when there is insufficient time for jig making."

One wonders whether Jones could have suspected the revolutionary implications of the abstract principle behind that very practical observation (i.e., that advances in machine tool control that expedited the making of jigs were fundamentally a way to expedite the cutting process itself, for which the jig was just a means to an end). The technological advances that led to the jig borer and NC were about to usher in the age of CNC and CAD/CAM, radically changing the way humans manufactured many of their goods. The awesome potential of control technology that would gradually eliminate many needs for jigs—and also often eliminate the need for the jobs of the operators who used them—was little appreciated outside of a few R&D laboratories when Jones recorded his insight.