Intermittent cutting generates mechanical and thermal impacts during the entry and cut-out stages, which adversely affect the tool's operational lifespan. In this study, rounded cutting edges with varying radii were prepared using brush grinding. Under consistent cutting conditions, intermittent turning simulations and experiments were conducted on ductile cast iron QT400-15. The experimental results revealed that as the cutting edge radius (CER) increases, the entry impact force and quasi-static forces in all directions also rise, with the feed force exhibiting the most pronounced increase. Under the test conditions, inserts with a CER of 40 μm demonstrated superior cutting performance. Compared to inserts with a CER of 10 μm, the tool life was extended by 37.5%, and the surface roughness of the machined surface was reduced by 16.9%. These improvements are attributed to several key factors, including a notable reduction in maximum tool stress, a slight redistribution of forces on the flank face, and minimal impact on the maximum cutting temperature as indicated by finite element simulation results. These enhancements contribute to increased resistance to chipping and deformation, as well as improved wear resistance of the tool.