Tube Hollows International

United States

BTA drilling is a form of precision deep hole drilling which, like gun drilling and trepanning, utilizes pressurized coolant, lubricant and a drill bit to form concentric bore holes. Named for a group of European manufacturers who formed an association in the 1940s (the Boring and Trepanning Association or BTA, ) BTA drilling is similar to gun drilling in that it reduces the core of the metal tube to chips, which are then evacuated during the drilling process. While trepanning preserves the metal core of a seamless tube, gun drilling and BTA drilling remove the inner core of the seamless tube, reducing it entirely to chips. Gun drilling and BTA drilling differ in how the lubricant flows to and away from the cutting carbide. In BTA drilling, the lubricant is pumped to the cutting edge around the outside of the bore, between the workpiece and the precision drilling tool. This forces the chips to flow back through the tube as they are evacuated. In gun drilling, the high pressure coolant and lubricant is delivered to the cutting edge down a central hole inside the drills shaft, and the chips of the metal core are removed through a V shaped groove on the outside of the drill.

Tube Hollows Internationals deep hole drilling expertise dates back more than sixty five years. In that time we have expanded our portfolio of capabilities to include other precision boring and machining processes. While gun drilling efficiently produces deep, concentric bores in barstock, gun drilled holes are typically less than 1.5 inches in diameter. For larger diameter holes, we typically rely on trepanning to efficiently remove large amounts of material. Like gun drilling, trepanning efficiently produces deep bores. With subsequent processing, THI can produce excellent concentricity in larger tubing sizes. Unlike gun drilling, trepanning leaves the core of the bar intact. Trepanning and gun drilling both use a high pressure coolant and lubricant to machine holes with excellent ID finishes and tight tolerances. But in gun drilling, the core of the bar is reduced to chips, which are then evacuated from the drill through a V shaped flute in the bit. Trepanning does not break down the center, solid core of the tube into chips, but rather leaves it intact for testing, reclamation or repurposing.