Carbide cutting tools in the cutting process (especially in intermittent cutting) cracks caused damage has been troubled by the problem of people working in the correct understanding of the causes of cracks and take appropriate preventive measures are the key tool to improve working life and cutting performance. Relevant research literature indicates that when cutting at high cutting speeds, the tool is easy to produce hot cracks and edge chipping increases. This paper analyzes the mechanism of cutting tests when intermittent cutting carbide cracks found in the cutting cycle the heating phase, the compression can cause thermal stress in the positive zone on the rake face of the cutting edge of a narrow band of local plastic blade deformation, then when the narrow zone in the external elastic material impact forced cooling again, there will be enough to cause visible cracks tensile stress, which verifies the thermal stress caused by the argument of the main causes of cracks carbide cutting tools.