Abstract
One of the practical ways to increase productivity of additive manufacturing (AM) and subtractive manufacturing (SM) operations is a reduction in the volume of the work material in part blanks used than for finishing machining operations. One of the most used ways is to make blanks with cored holes. In AM, it significantly reduces the time needed to make a blank and cost of raw material(s) spent per blank; in both AM and SM, it increases productivity and efficiency of hole-making operations. In practice, drilling/reaming of cored holes involves a major difficulty; the axis of the cored hole is always shifted (with rather generous tolerance) from that of the finished hole. This chapter presents a step-by-step development of the basic drill design for cored holes. A new design concept was developed; practical drills according to this concept were made, tested, and implemented for drilling cored holes. The test and implementation result showed a two- to threefold increase in tool life with no drill premature failures