Although index tools are increasingly used in wide range, brazed carbide tools are extensively applied in all kinds of high speed metal machining for their simple and compact structures, high rigidity and flexibility. So it is important to investigate the tool damage of brazed carbide tools. In the research, to avoid residual stress and micro cracks, the insert trough is specially designed and the parameters of braze-welding and heat treatment are optimized. After being brazed and sharpened, the tools were checked to assure no obvious defects in brazed tools. Then 50 pieces flawless turning tools of 45°, 90° and parting-off, respectively, were selected and used in high speed turning experiments. After turning experiments, there were seven damage types of fracture tools and the main fracture modes were notch, chipping, tip collapse and tip-off for all kinds of tools. Notch damage accounts for about 30% of 45° and 90° fracture tools. Micro tipping and extend-tipping are main fracture modes and in relatively high proportion to the total amount of 45° and 90° straight tools. Tip-off is the main breakage form of cut-off tool and accounting for about 58% of total fracture tools. How the residual stress, micro crack, cutting parameters and material defect, et al, cause tool fracture damage is detailedly analyzed.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.