OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 5 No. 4 2023 It is shown that the design of a drill with a cutting wedge part and a cutting edge with a large value l can have both positive and negative effects on the tool life. With a short duration of such a section, the element of the cutting wedge acts as a stress concentrator and takes a significant part of the bending load, while in the case of a longer section with a smooth change in angle, the forces are evenly distributed over the cutting wedge. Therefore, later design can significantly increase the resistance to brittle fracture. This effect can be enhanced by the uniformity of cross-sectional area of the cutting wedge along the cutting edge. The established patterns serve as the basis for the design methodology for drills with a toroidal flank surface and as a prerequisite for the development of a comprehensive CAD for twist drills. This work is important for understanding the geometric design features of drills with a non-standard flank surface shape. After confirming the relevance of using drill designs with a new sharpening form, the logical development of this work would be revealing the analytical relationships between the shape of the cutting edges, the helical flute and the shape of the flank surface. Conclusions 1. In this study, a comprehensive methodology for designing drills with a toroidal flank surface is proposed in this work for the first time, including the development of new designs of drills with a toroidal flank surface. The CAD algorithm for toroidal flank drills is discussed in detail when designing each functional surface in the solid-state modeling system. 2. A comprehensive study of the effect of changing the radius of the generatrix of the flunk surface on the value of the rake angles in order to identify the best geometric parameters of the tool on various designs of drills with a toroidal flank surface and its application field is carried out. It is pointed out that with a decrease in the radius of the generatrix of the flank surface, the range of changes in the rake angle and the sharpening angle of the cutting wedge decreases compared to the design of drills with conical sharpening of the flank surface. It is also found that a tool with a minimum permissible radius of the generative of the flank surface has the best distribution of rake angles and sharpening angles of the cutting wedge along the entire cutting edge. The range of variation of the rake angle decreased from [-18°; 25°] to [2°; 25°], which indicates a decrease in range by 86 %. The range of changes in the sharpening angle of the cutting wedge decrease from [58°; 77°] to [56°; 68°], which indicates a decrease in range by 56 %. Drills with such sharpening of the flank surface can be used without additional sharpening to the center, since the rake angle is in the positive range of values up to the section where the main cutting edge transitions into the chisel edge. It is proved that the sharpening angle of the cutting wedge has a value close to constant up to 0.45 lt/l, while the range of the sharpening angle decreased from [58°; 68°] to [56°; 58°], which indicates an improvement in geometric parameters up to 5 times. These indicators exceed those for all the existing twist drill designs. 3. Based on FEМ, it is shown that the equivalent stresses in the cutting wedge reduced from 4644.62 MPa to 2003.1 MPa due to the use of drills with a toroidal flank surface with a minimum generatrix radius, indicating a stress reduction by a factor of 2.31. At the same time, the maximum equivalent stresses decreased from 1064.85 MPa to 499.1 MPa , indicating a stress reduction by ~ 2.13 times. References 1. Kozhevnikov D.V., Grechishnikov V.L., Kirsanov S.V., Kokarev V.I., Skhirtladze A.G. Rezhushchii instrument [Cutting tool]. Moscow, Mashinostroenie Publ., 2007. 528 p. ISBN 978-5-217-03373-7. 2. Semenchenko I.I., Matyushin V.M., Sakharov G.N. Proektirovanie metallorezhushchikh instrumentov [Design of cutting tools]. Moscow, Mashgiz Publ., 1963. 952 p. 3. ZengT., Chen Z.C., Liu Z.,Yi Z.,Wang S.An applied explicit mathematical model of conical drill point geometry without flank rubbing. The International Journal of Advanced Manufacturing Technology, 2020, vol. 106 (9–10), pp. 3707–3720. DOI: 10.1007/s00170-019-04759-y. 4. Petukhov J.E., Vodovozov A.A. Spiral’noe sverlo s krivolineinymi rezhushchimi kromkami [Twist drill with curvilinear lip]. Patent RF, no. 2528593, 2014.
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