Abstract: A technique of detecting cutting fracture by simultaneous monitoring both the spindle motor motor and acoustic emission (AE) during the cutting process is reported.A holler current sensor and a new type of AE sensor which transmits the AE signal through the lubricant are used to catch the required signals. The comprehensive estimation principle of cutting tool fracture, monitoring plan, and experimental results are introduced. The drills breakage with diameter over 0.6mm and turning and milling cutters'crack with area over 0.2mm2 can be detected automatically by the system The rate of success in detection approaches 98% or higher.