The invention relates to a portable power tool including, within a housing (2, 4): an electric motor (10) having a drive shaft (12), an epicyclic reduction gear (20) having planetary gears (25) meshing with a central gear (26) of the drive shaft (12) of the electric motor (10), the reduction gear being provided with an output shaft (32) that is rigidly connected to a ball screw (34) of a ball screw/nut mechanism (30) and is coaxial to the ball screw (34), and a support bearing (PS1) connecting the output shaft (32) to the housing (2, 4). In accordance with the invention, the tool includes at least one stabilization bearing (PS2, PS2a, PS2b, PS2c) axially offset relative to the support bearing (PS1). The stabilization bearing (PS2, PS2a, PS2b, PS2c) connects the output shaft (32) of the epicyclic reduction gear (20) to the housing (2, 4) by means of at least one intermediate part selected from: the drive shaft (12) of the electric motor (10), planet-carrier axles (24) of the epicyclic reduction gear (20), and
