Polycrystalline cubic boron nitride (PCBN) is formed by sintering cubic boron nitride particles (cBN) at high temperature and high pressure. In this process, a network of cBN particles is formed by intergrowth and bridging between the particle phases. The response of the aggregate to applied stresses in process such as hard machining, will therefore principally involve the deformation of this skeletal structure. In this work, the microstructure and hot hardness and adhesion properties of three high-density PCBN aggregates were comparatively studied. The results were correlated to their cutting performance and wear modes in machining a carbide-based hardfacing material.