Thread tightening mechanism and thread tightening device

The utility model relates to a thread tightening mechanism and a thread tightening device. The thread tightening mechanism comprises a rotary grabbing assembly and a pre-tightening assembly. The rotary grabbing assembly comprises a grabbing fixing frame, a motor and a grabbing pneumatic clamping jaw. The pre-tightening assembly comprises a pre-tightening fixing frame, a driving cylinder, a floating column and a spring arranged on the outer side of the floating column in a sleeving mode, an upper limiting piece and a lower limiting piece are arranged on the floating column, a through hole is formed in a connecting plate of the grabbing fixing frame, the spring is arranged between the upper limiting piece and the connecting plate, and the lower limiting piece is arranged below the connecting plate. The thread tightening device comprises a workbench, a lifting driving mechanism and a thread tightening mechanism, the pre-tightening fixing frame is arranged on the lifting driving mechanism, in the whole tightening