Big hole positioning and clamping device

The utility model discloses a big hole positioning and clamping device, which has a pedestal (3); a cylinder (1) is mounted on the lower end of the pedestal (3); a piston in the cylinder (1) is connected with a piston connecting rod (4) mounted in a connecting rod through hole of the pedestal (3) by a piston rod (2); the back and front side of the pedestal (3) are respectively fixed with a half-opened pin (11) extended outside the upper end of the pedestal (3); the upper end of the piston connecting rod (4) is connected with a left and a right chuck (10) by a left and a right pin (6) respectively; the left and the right chuck (10) are respectively connected with one end of a connecting rod (8) by a pin (9); the other end of the connecting rod (8) is connected on the half-opened pin (11) by a pin (7). Compared with prior arts, the apparatus solves the problems of current chucks including corpulent structure, welding channel occupation, inadequate clamping force and too small pin diameter.