An operating instrument includes a housing, a chassis, a first and second drive shaft, a gear assembly, a switch assembly, and a bearing lock assembly. The first and second drive shafts each has a first portion supported by the chassis in the housing and a second portion extending out of the housing. The gear assembly includes a first gear member fixedly received on the first portion of the first drive shaft and a second gear member slidably received on the first portion of the second drive shaft. The switch assembly is operable to place the second gear member into engagement with the first gear member thereby coupling the second drive shaft with the first drive shaft to provide a first operating mode wherein the second drive shaft is rotatable with the first drive shaft, or displace the second gear member out of engagement with the first gear member thereby decoupling the second drive shaft from the first drive shaft to provide a second operating mode wherein the second drive shaft is non-rotatable with the first drive shaft. The bearing lock assembly is operable to lock the first and second drive shafts to the chassis whereby the first and second drive shafts are restricted from sliding out of the housing and are capable of freely rotating or unlock the first and second drive shafts from the chassis to allow the first and second drive shafts to slide out of the housing.
