Expanding device for inner hole of flexible gear

The utility model discloses an opening device for a flexible gear inner hole, and particularly relates to the technical field of flexible gear machining assistance of harmonic reducers. The utility model discloses an expanding device for an inner hole of a flexible gear. A lead screw assembly comprises a lead screw and a lead screw nut arranged on the lead screw. The tensioning assembly comprises a step core shaft and a tensioning sleeve assembly, wherein the step core shaft is provided with at least two step shafts with different diameters, and the step core shaft is sleeved with the tensioning sleeve assembly. The tensioning sleeve assembly comprises an expansion sleeve and an elastic ring, wherein the expansion sleeve is composed of a pair of semicircular expansion sleeves which are separated from each other. The step mandrel is arranged on the lead screw nut in a sleeving mode and connected with the lead screw nut. The semicircular expansion sleeve is sleeved on the step shaft of the step mandrel through