A power tool (1) for driving a working tool (3) that penetrates at least axially into a to-be-machined material (2), and including a signal processor (6, 6'), and a transducer (5) which is suitable for exciting and detecting a high-frequency electromagnetic wave (4) propagating axially along the working tool (3) and which is connected to the signal processor (6, 6') that is designed to determine the penetration depth (T) of the working tool (3) into the material (2) based on high-frequency electromagnetic waves (4).