Back Boring Bars used to machining of a bore that cannot be reached opposite direction.There are three general types of boring bars: high speed steel, brazed carbide, and indexable carbide.A boring bar is a tool used in metalworking and woodworking. Boring is a technique used in many aspects of building. when concentricity of the outer and inner diameters is important, external turning and boring should be completed in a single set up.