Tungsten Carbide Gun Drill Guide Pad

The BTA deep hole drilling process is commonly used to machine boreholes with a large drilling depth-to-diameter ratio (l/D) and outstanding workpiece quality. The asymmetric tool design leads to a nonzero radial component of the cutting force and the passive force, which are conducted to the borehole wall by so-called guide pads. These guide pads smooth the borehole wall by a forming process and improve the surface quality. Processes, that machine materials with a high adhesion tendency, such as high alloy stainless steel, suffer from poor surface quality in the borehole and the adhesion from the workpiece material on the guide pads. In this paper modified Diamond-Like-Carbon (DLC) coated guide pads for BTA deep hole drilling tools are investigated. The scope of the experiments was the reduction of the adhesion by reducing the friction coefficient of the guide pads, as well as the improvement of the quality of the borehole wall.