BTA is the acronym from Boring and Trepanning Association which developed the BTA system. It involves a single drill tube in which high pressure coolant is supplied to the drill through the annular area between the drilled hole and the tube outer diameter. The chips are evacuated through the interior diameter of the tube. Compared to Gun Drill system, BTA allow removing much thicker metal area, obtaining wider diameter holes. The minimum diameter is 10 mm.
BTA deep hole drilling machines with ejector system are evolved from classical BTA machines. It is a system with twin tubes where the coolant is pumped through the space between the inner and outer tube. This eliminates the use of pressure head and simplifies the system. This was introduced mainly to tool up conventional machines to do Deep Hole Drilling. The ejector system can process holes with minimum 16 mm diameter, due to the double tubes system.