Multi-flute drill-broach for precision machining of holes

This paper deals with hole-enlarging multiflute drill processing. The analysis of existing structures, their advantages and disadvantages is carried out. Cutting conditions during hole-enlarging multiflute drill processing are shown. A new design of hole-enlarging multiflute drill as a hole-enlarging multiflute drill-broaching tool from broaching-speed steel with carbide plates, as well as a new way of handling the new tools is offered. Hole-enlarging multiflute drill-broaching combines the features of hole-enlarging multiflute drill (in cross section) and the features of broaching tool (in longitudinal section). In this way, it was possible to increase the quality of hole making (size variance, surface roughness), to facilitate the cutting conditions and to increase the durability. The results of prototypes testing are presented.