The invention discloses a positioning clamping device suitable for
machining a single-head
screw pump rotor. The device comprises a
machine tool body, a
workbench and a clamping mechanism, wherein the clamping mechanism comprises a base, two sealing covers, an outer shell, an inner shell, a
piston plate, a sealing plate, a driving disc and a plurality of clamping jaws, the inner shell is arranged in the outer shell in a sleeved mode, a working cavity is formed between the outer shell and the inner shell, the driving disc, the sealing plate and the
piston plate are sequentially arranged in the working cavity, and a first air hole and a second air hole are formed in the outer shell. According to the device, the first air hole and the second air hole are connected with an air source, air is introduced, and the
piston plate is pushed to reciprocate in the axis direction of the inner shell, so that the driving disc is driven to reciprocate, the plurality of clamping jaws are driven to synchronously slide along wedge-shaped grooves in the driving disc, contraction and expansion of the clamping jaws are achieved, automatic workpiece clamping and loosening are achieved, workpiece mounting operation is simple and rapid, workpieces can be effectively clamped, and the
machining precision of the workpieces is guaranteed.