The deficiency in the variety of available magnetic abrasive results in a narrow range of finishing performance. To break through this difficulty, this research developed iron-based gas-atomized magnetic tools. The magnetic tool has a spherical shape and micro-crevices on the surface. The micro-crevices perform the role of cutting instead of the edges of the existing magnetic abrasive, thereby achieving abrasive-less finishing. This paper studies the finishing performance of the developed magnetic tool. Compared to the existing magnetic abrasive, this magnetic tool shows more efficient finishing performance in the internal finishing of SUS304 stainless steel tubes used for sanitary piping systems.