Mechanical device for preventing overload of main shaft

The invention discloses a mechanical device for preventing overload of a main shaft, which relates to the field of numerical control machining centers and comprises an outer sleeve, an inner sleeve and an inner sleeve, the inner sleeve is arranged on the periphery of the main shaft in a sleeving mode, and the outer wall of the inner sleeve is attached to the inner wall of the outer sleeve in a sliding mode; the hydraulic system is arranged on the spindle box and comprises a one-way valve, an oil cavity and an overflow valve assembly, and the one-way valve is communicated with the overflow valve assembly through the oil cavity; when hydraulic oil is discharged from the one-way valve, the storage space of the hydraulic oil between the inner sleeve and the outer sleeve is an oil cavity; when the main shaft retracts, the hydraulic oil stored in the oil cavity is discharged through the overflow valve assembly; the mechanical device is a safety protection device for preventing the main shaft from being damaged due