Fault detection functions of a robotic manipulator are very useful for factory automation. All production has the possibility to fail due to unexpected accidents. To reduce the fatigue of human workers, small errors automatically should be corrected by a robot system. In this paper, an external thread fastening task by a robotic manipulator is investigated. To discriminate the four states of a task, linear support vector machine methods with two feature parameters are introduced. One is the estimated insertion length, and the other is the maximum reaction force. The effectiveness of the proposed algorithm is confirmed through an experiment and recognition examination.