Press fit joint comprising inner and outer members having coacting complementary tapered press fit surfaces, an annular piston secured to one of said members and slideable relative to the other of said members, means defining an annular recess in said other member, said piston defining with said recess an annular enclosed chamber for a pressure medium moveable with said other member, means defining a first radial channel in said other member terminating in a circumferential groove communicating with said tapered surfaces and spaced axially from said annular chamber, said channel adapted to be connected to a pressure medium whereby the pressure medium flows between the tapered surfaces and gradually fills the enclosed annular chamber thereby to effect axial displacement of said inner and outer members relative to one another.