In this study, the milling of submillimeter-deep stepped micro-grooves on nitrile rubber surfaces was investigated. Rubber products with microstructured surfaces are typically manufactured by molding, which is costly and unsuitable for prototyping or small-lot production. Machining provides a promising alternative but faces challenges due to rubber’s flexibility and elastic deformation. Experiments were conducted using a numerically controlled milling machine and cemented carbide end mills with different twist directions and angles. The experiments compared left-twist and right-twist tools, whereras left-twist tools have cutting edges twisted opposite to the conventional right-twist tools. The effects of twist angle and feed rate on burr formation and dimensional accuracy were evaluated in detail. As a result, burr formation was notably suppressed with the left-twist tool, especially at larger twist angles and lower feed rates. In contrast, right-twist tools produced significant burrs and residues due to chip deformation and bouncing. Moreover, cross-sectional profiles measured by laser profilometry revealed that depth errors decreased as feed rate and twist angle decreased. These errors are attributed to elastic deformation and recovery of the rubber surface induced by cutting forces. These findings demonstrate that appropriate tool geometry and machining parameters can achieve burr-free, high-precision stepped microgroove milling on nitrile rubber. These results also provide important insights for the cost-effective and rapid manufacturing of rubber products with microstructured surfaces, especially suited for small-lot and prototype production.

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