In order to support optimum design of cutting conditions on machining centers, now techniques that can measure and monitor cutting torque on processing are wanted. However, it is difficult to measure cutting torque on small diameter tool processing because of small range. The purpose of this study is to develop the system that can measure small cutting torque on processing. The measurement method is to detect torsion angle of magnet coupling in the system caused by cutting torque. This paper explains the system and considers calibration means of error factors to let measurement accuracy down. Recent Wire Electrcal Discharge Machine (WEDM) has reached machining accuracy of 1-2 μm and surface roughness of 0.3-0.5 μmRz. To improve the performance of WEDM, a high-frequency AC (HFAC) power supply is used for the finishing process. Meanwhile, the mean voltage while machining is 0 volt, which makes difficult to capture the discharge gap voltage for proper servo control of wire electrode position. Therefore, constant feed rate system has been adopted instead of servo control when using of HFAC power supply. It is one of major problems to process a super-fine profile. By adding a new electrical circuit between the workpiece and the wire electrode, the equivalent discharge gap voltage is properly detected, and the feed rate can be calculated properly. This new servo control method helps the improvement of the accuracy with super-fine profiles such as IC lead frame stamping die. And it also improves the minimum discharge gap with fine wire electrode, such as 4 μm with 30 μm diameter wire electrode, and 1.5 μm with 20 μm diameter wire electrode.