Jig borer
Encyclopedia
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 maker
s with a higher degree of positioning precision (repeatability) and accuracy than those general machines had previously provided.
A typical jig borer had a work table of around 400 x 200 mm, which can be moved using large handwheels (with micrometer-style readouts and verniers) on particularly carefully made shafts with a strong degree of gearing; this allowed positions to be set on the two axes to an accuracy of 0.0001 inch (2.5 micrometres). It was generally used to enlarge to a precise size smaller holes drilled with less accurate machinery in approximately the correct place (IE with the small hole strictly within the area to be bored out for the large hole).
(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:
Franklin D. Jones, in his textbook Machine Shop Training Course (5th ed), recorded insightfully:
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.
Machine tool
A machine tool is a machine, typically powered other than by human muscle , used to make manufactured parts in various ways that include cutting or certain other kinds of deformation...
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
Milling machine
A milling machine is a machine tool used to machine solid materials. Milling machines are often classed in two basic forms, horizontal and vertical, which refers to the orientation of the main spindle. Both types range in size from small, bench-mounted devices to room-sized machines...
that provided tool and die maker
Tool and die maker
Tool and die makers are workers in the manufacturing industry who make jigs, fixtures, dies, molds, machine tools, cutting tools , gauges, and other tools used in manufacturing processes...
s with a higher degree of positioning precision (repeatability) and accuracy than those general machines had previously provided.
A typical jig borer had a work table of around 400 x 200 mm, which can be moved using large handwheels (with micrometer-style readouts and verniers) on particularly carefully made shafts with a strong degree of gearing; this allowed positions to be set on the two axes to an accuracy of 0.0001 inch (2.5 micrometres). It was generally used to enlarge to a precise size smaller holes drilled with less accurate machinery in approximately the correct place (IE with the small hole strictly within the area to be bored out for the large hole).
History
Before the jig borer was developed, hole center location had been accomplished either with layoutMarking out
Marking out or layout is the process of transferring a design or pattern to a workpiece, as the first step in the manufacturing process...
(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
Numerical control
Numerical control refers to the automation of machine tools that are operated by abstractly programmed commands encoded on a storage medium, as opposed to controlled manually via handwheels or levers, or mechanically automated via cams alone...
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 inch) 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
Cam
A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion or vice-versa. It is often a part of a rotating wheel or shaft that strikes a lever at one or more points on its circular path...
, 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.