A hydraulic camshaft phaser includes an outer rotor and an inner rotor rotationally adjustable and arranged concentrically about a common axis of rotation. At least one hydraulic chamber is formed between the outer rotor and the inner rotor, into which hydraulic chamber at least one connected vane extends from each of the outer rotor and the inner rotor, thereby dividing the hydraulic chamber into at least one pressure chamber pair formed by two pressure chambers. The inner rotor has a circular opening extending concentrically along the axis of rotation, a sealing portion being formed on the inner surface of the circular opening between two axial faces of the inner rotor, and the opening having a larger inner diameter on both sides of the sealing portion than in the sealing portion. The inner rotor is a sintered part, and the sealing portion of the inner rotor is calibrated.