Abstract: The machine for trimming pieces of wood, such as a surfacing, planing or other machine, comprises a rotary tool having a tool holder provided with projecting axially extending blades and adapted to machine at least one surface of the piece of wood. This tool has, on the input side and output side thereof, two driving rollers for driving the pieces of wood. These rolls have axes parallel to the axis of the tool and are connected to rotate with the latter by a speed reducing mechanism. The mechanism employs a sun and planet train one of the sun wheels of which is mounted directly on the shaft of one of the driving rollers. Another sun wheel is freely rotatable on this shaft and is prevented from rotating relative to the frame of the machine.