Automatic centering three-point bending test clamp

The utility model provides an automatic centering three-point bending test fixture, which relates to the field of rock mechanical property testing, and comprises a pressure head assembly with an extrusion part in the middle, a sliding support, a base, a fixed support and a transmission assembly with an operation part, and the transmission assembly comprises a right-handed rotation bolt and a left-handed rotation bolt which are in transmission connection; the fixed support is fixed on the base, two opposite ends of the fixed support and the base are provided with grooves, and the pressure head assembly is fixed on the two grooves; the sliding supports are arranged on the two opposite sides of the fixed support and the inner wall of the base, and the right-handed rotation bolt and the left-handed rotation bolt are movably connected with the two sliding supports respectively. A V-shaped groove is formed in the sliding support, a first supporting roller is fixed at the upper end of the sliding support, and the pr