The first operation in producing a gun barrel is deep hole gun barrel drilling. The three major components for a deep hole gun barrel drill are:
– the driver which holds the drill in the machine;
– the shank which connects the driver to the tip; and
– the tip, typically made of solid carbide, which performs the cutting.
There is a hole running down the center of the drill to supply coolant oil while drilling. When
drilling, the work turns at between 5000-7000 RPM (revolutions per minute), and the drill feeds into the work at between 1 ¾ and 3 IPM (inches per minute). Both the feed rate and RPM are dependent upon the drill diameter. As the drill feeds into the work, coolant which is being pumped down the center of the drill flushes the chips from the barrel into the bed of the machine. This procedure does not produce a surface smooth enough for a finished bore, nor does it hold the required diameter tolerances throughout the gun barrel. None of the toolmarks generated by the barrel drilling will remain in the finished barrel, if the barrel is subjected to the reaming process.
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