Due to significant increase in the incidence of cardiovascular disease, the development of medical devices to treat thrombosis has recently been of great concern. In order to develop a rotational tool to remove vascular blood clots, it is especially important to understand the tribological behavior of the tool inside a vessel to effectively remove blood clots without any damage to the vessel. In this work, the grinding behaviors of different tools were experimentally investigated using clotted blood samples from cattle. Three tools of different shapes were designed and tested. We found that an elliptical design tool with four stainless steel blades (0.25 mm-thickness) yielded the smallest clot particles. In experiments using two other tools with stainless steel and fluoro carbon wires, stainless steel generated small particles more efficiently than fluoro carbon. Particle size decreased as the contact length of the tool edges and the rotational velocity of the tool increased. It is expected that the results of this work may be used to design superior devices for a variety of medical applications related to clot removal in blood vessels.