Automatic centering and clamping mechanism for worktable

The invention discloses an automatic centering and clamping mechanism for a worktable. The mechanism is used for positioning a disc-like work piece (100), the disc-like work piece (100) is provided with an axial reference plane (11) and a radial reference plane (12), the mechanism is characterized by comprising at least two ejection assemblies and a matched top drive mechanism, wherein the ejection assemblies are uniformly distributed in the circumferential direction by taking the center of the worktable as a circle center and are connected with the top drive mechanism, when the axial reference plane (11) of the disc-like work piece (100) is located at the top drive mechanism, the top drive mechanism drives the ejection assemblies to exerting acting force to the radial reference plane (12), the acting force is used for radially clamping the work piece, and when the axial datum surface (11) of the disc-like work piece (100) is disengaged from the top drive mechanism, the ejection assemblies withdraw the acting