LAUSR

Abstract Overcoming the myriad challenges in the high-speed machining of Inconel 718, especially for deep-hole drilling (DHD), has been a long-standing area of research for several manufacturers and researchers. Owning to the difficult-to-machine characteristics of Inconel 718, the traditional carbide-tipped gun drills often get worn at an accelerated pace and require repetitive re-sharpening or replacement. This lowers productivity and increases costs. Furthermore, it is also a challenging task to meet the stringent hole-straightness requirement of 1/1000 mm for DHD of such difficult-to-machine materials, especially using those carbide gun drills. Hence, this study presents a development of polycrystalline cubic boron nitride (PCBN)-tipped gun drill to address the rapid tool degradation and poor hole-straightness issues. The developed PCBN-tipped gun drill has a layer of PCBN on its cutting tip and bearing pads. Several gun drilling tests on Inconel 718 have been performed at high drilling speed conditions to assess the performance of developed gun drill. In contrast to traditional carbide-tipped gun drills, the developed PCBN-tipped gun drill has the capability of not only performing in the higher cutting speeds but also reducing drilling forces, drilling torques, and tool wear. Furthermore, the surface quality of drilled holes is also much better than those drilled by traditional carbide gun drills. With these results, it further validates the credibility of the developed PCBN gun drill in enhancing the deep-hole drilling process with high throughput productivity and superior quality of drilled holes, especially for difficult-to-machine materials.