<p>This paper presents a novel magnetic tool based on custom-made diametrically magnetised permanent magnets, designed and developed for finishing ferromagnetic cylinders using a magnetorheological fluid (MR) based abrasive finishing (MFAF) process. The present study aims to provide cost-effective, efficient, and viable industry solutions to address challenges associated with the surface finish of ferromagnetic cylinders using MR fluids. Existing finishing methods for ferromagnetic cylinders either use electromagnetic setup or permanent magnetic strips, which do not provide a high-intensity uniform magnetic field within inner profile of cylinder workpiece. In conventional MR fluid-based MFAF processes, the finishing is hindered by induced magnetism, which causes MR fluid to adhere to the workpiece surface, thereby impeding effective abrasive interaction and reducing material removal efficiency. To overcome these limitations, custom-designed diametrically magnetised NdFeB permanent magnets are designed, developed, and integrated into a novel cylindrical magnetic finishing tool. A novel cylindrical magnetic finishing tool incorporating these magnets is designed, developed, simulated, and experimentally validated to achieve optimum magnetic flux intensity and its uniform distribution on the cylindrical working surface. Significant improvement in surface roughness (∼ 80%) has been achieved using the novel magnetic tool. Both simulation and experimental results support the statement, validity, and effectiveness of the novel design and configuration based on diametrically magnetised magnets to achieve a high-quality surface finish for ferromagnetic cylinders. The newly designed magnetic tool offers promising industrial applicability for ferromagnetic cylinders’ precision and high-quality surface finish.</p> Graphical Abstract <p></p>