Groove cutting experiments were carried out in order to investigate the effect of tool vibration on the brittle–ductile transition. The workpiece of fused silica was inclined by a small angle onthemounting plate so that the depth of cut can vary continuously in one revolution of the spindle. A singlecrystal diamond cutting tool with a rake angle of 08 and a nose radius of 0.8 mm was used. The maximum vibration speed of the cutting tool is 45 m min1. The feed rate is chosen to be large enough so that the grooves are generated without interference