Abstract: A cutting force sensor for measuring the variation of cutting force in a cutting machine includes a screw shape body to serve as a locking screw in a turret of the machine. The sensor has a pair of strain gauges at one end of the sensor to measure and detect the cutting force variations of a cutting tool held by the turret and send the signals to a pair of Wheatstone Bridges located at another end of the sensor. The signals are then filtered, amplified and analyzed for monitoring the cutting tool wear and/or breakage condition. The sensor is located close to the cutting point and therefore can generate high S/N (Signal/Noise) ratio and produces more precise measurements. The sensor is of low cost and does not take additional space and can be readily used in an existing machine without requiring expensive structural changes.