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 drill’s shaft, and the chips of the metal core are removed through a “V” shaped groove on the outside of the drill.
Typically BTA and trepanning machines drill holes in the 1.5 inch and larger range.
BTA drilling uses more power than gun drilling, but is an excellent alternative for boring holes in difficult to drill metals and exotic alloys. It is also especially effective when the core material being removed is so unyielding that it is difficult to break up into chips (e.g. stainless steel or hafnium).
The oil and gas, aerospace and defense and nuclear power industries rely on BTA drilling because it produces precision holes with tight tolerances in very difficult to drill materials. The hostile, extreme environments present in these industries demand premium precision seamless tubing which is corrosion resistant, highly concentric and able to withstand variable and high pressures and temperatures without the risk of rupture, scaling or the introduction of surface imperfections. BTA drilled tubing is found in vital control and communication lines between down hole tools and above ground crews on oil rigs. It's also used in nuclear reactors, MRI machines, x-ray machines and other technologically advanced equipment.
Tube Hollows International uses BTA drilling to produce tubular components and heavy wall seamless tubing with IDs in the 3" – 5" range.