Gun Drilling and Deep Hole Drilling

Gun drilling and deep hole drilling are the techniques used to produce straight and accurate holes in work-pieces that are much larger than conventional drills are capable of. They are primarily performed on specialized, dedicated equipment that consists of dual spindles to rotate the work-piece as well as a cutting tool to perform the machining.

Gun Drilling: The oldest method of deep hole drilling, gun drills use a long, thin cutting tool to produce holes in metal work pieces that are far beyond the capabilities of conventional style drills. Initially invented for the barrels of guns, which famously required extremely precise and straight bores, the process has since been refined to provide high-performance and reliability on modern dedicated machinery.

Deep Hole Drilling: The next method of deep hole drilling is STS (Single Tube System) or BTA drilling, which uses external coolant flow and internal chip removal to achieve a higher level of surface quality in the work piece. These methods are typically performed on BTA-style deep hole drilling machines with single-tube and multiple-tube heads that pass the lubricant and coolant through an internal drill pipe to a single cutting edge.

The high pressure coolant that is pumped through the tool pipe to the cutting edge helps push chips up and out of the hole while providing better cooling and lubrication. A solid carbide tip and a pathway through the shank that allows chips to move back out of the hole are also important features in this technique. It is possible to drill holes from 1mm to 50mm deep with this method.