extends over the outer surface of the shaft mounting portion and having an outer surface wherein the carbon fiber layer outer surface has a non smooth surface structure wherein the injection molded interface element mounting portion is injection molded over the carbon fiber layer surface structure the method according to claim 12 further comprising preparing of shaft mounting portion before wrapping a carbon fiber layer for establishing a reliable connection between the shaft and the carbon fiber layer application_number US 201414175346 A description fig1 illustrates a shaft 10 in particular a reamer shaft having a mounting portion 11 the shaft 10 has an outer surface onto which a carbon fiber layer 30 is wrapped fig1 illustrates the carbon fiber layer 30 in an unwrapped condition fig2 illustrates the end portion of a shaft 10 wherein the carbon fiber layer 30 is wrapped around the outer surface of the mounting portion 11 as can be seen from fig2 the carbon fiber layer comprises a surface structure 34 on the outer surface 33 of the carbon fiber layer this outer structure may be formed for example as a tooth structure or a rippled or ripped structure wherein ripples or rips run along a longitudinal direction of the shaft 10 it should be noted that the rips of the surface structure 34 may also run in a helical way in order to carry not only circumferential forces e g torque forces but also forces in a longitudinal direction of the shaft like pushing or pulling forces it should be noted that the surface structure 34 may also have any other structure being capable of transmitting forces from the shaft 10 to an.