BTA drilling is a deep hole drilling process that uses specialized drilling tools on long drill pipes to drill deep holes in metal, ranging from holes with a diameter of 20 mm [0.80 in] or larger to as deep as 400:1 diameter ratio. BTA drilling is the most efficient method of drilling deep holes because it is a cleaner, more reliable and more powerful process than traditional twist drilling and can achieve larger diameters and higher feed rates than other gun drills.
BTA drilling bits are threadedly mounted on the drill pipe and use multiple cutting surfaces on a single tool to effectively remove chips. High-pressure coolant is used to expel the chips through the holes in the bit and then out of the drill pipe. BTA drill bits are available with brazed inserts or indexable carbide inserts.
BTA stands for Boring and Drilling Association and is sometimes referred to as STS (Single Tube System) drilling because it uses one drill pipe as the BTA tool, whereas other processes (such as ejection drilling) use two.
Processing of deep holes with large diameters, 20mm or more, length ratio of 10:1 or more, maximum over 400:1