Longer tools can be used, but it becomes necessary to have special guide pads in the throat of the trepanning tool in order to support the weight of the lengthening slug that is being created.
Most trepanning tools start at a diameter of at least 2" and in some cases can produce holes of 10" in diameter or larger.
Trepanning tools require significantly lower horsepower than solid drills in most cases the power consumed will be less than half of what is needed for a solid drill.
Many of these alloys cannot be drilled, but can be cut with a trepanning tool.
The trepanning tools were originally developed for, and have been used extensively in, the stell fabrication and erection industries, and other applications using magnetic drill units.
Pin-type gundrills, Figures 9 and 10, work like a trepanning tool
that cuts from the solid and generates an accurately controlled pin or core.
Other drawers contain replicas of Neolithic flint trepanning tools
, used to bore holes into patients' heads--human remains show that some people survived this ordeal as well as tonsil guillotines, which performed thousands of needless tonsillectomies before the operation fell out of fashion.
produce holes faster than more conventional tooling.