Nut internal screw thread detection machine

The invention discloses a nut internal screw thread detection machine. The nut internal screw thread detection machine comprises a frame, a rotatable nut disposing disc and a telescopic screw thread detection manipulator. The screw thread detection manipulator comprises a stepping motor, a torque force sensor, a screw thread gauge clamp connected with a screw thread gauge, and a displacement sensor for detecting the displacement of the screw thread gauge; the nut disposing disc is provided with a plurality of penetrating step holes; and the screw thread gauge comprises a lower limit screw thread gauge which is arranged at a lower position and can pass through the step holes, and an upper limit screw thread gauge. By adopting such a structure, the lower limit screw thread gauge performs lower limit screw thread detection on nuts to be detected, if the nuts to be detected are qualified, the lower limit screw thread gauge passes through the step holes; and if the stepping motor continues to move downwards, the upper limit screw thread gauge directly performs upper limit screw thread detection on the nuts to be detected. According to the invention, the lower limit and upper limit screw thread measuring of the nuts to be detected can be rapidly realized for once simply by use of one screw thread detection manipulator, the structure is simple, the size is small, the manufacturing and purchasing cost is low.