This paper presents the development of new rotary drilling fasteners intended for copper ore mining applications. The study addresses durability and reliability issues of drill string connections subjected to high mechanical loads and fatigue. Improved thread geometries were designed to reduce stress concentrations and facilitate assembly and disassembly. Numerical analyses based on von Mises stress criteria were performed to compare the proposed designs with standard fasteners. Prototype components were manufactured using additive techniques for preliminary functional evaluation. The results show a more uniform stress distribution, with up to 28.4% reduction in surface stresses for the C17 fastener relative to the reference design. Prototype testing confirmed proper thread engagement and stable contact between the drill tip and fastener collar. The redesigned fasteners provide increased durability, easier handling, and improved operational reliability, supporting safer drilling under difficult geological conditions. The solution has been successfully implemented in industrial practice.