An arrangement for centering an end wall of a housing of a hydraulic gear machine, such as a pump or a motor, with respect to the open end of an internal chamber provided in a housing body forming the circumferential wall of the housing includes a plurality of pins which are received in a press-fitting manner in bores of the end wall and protrude beyond an end face of the end wall which faces and closes the open end of the chamber in the mounting position. The pins may have contact surfaces which are turned to the same diameter as the corresponding inner surface of the housing body which bounds the open end of the chamber, or they may exactly fit into the open end, or overlap slightly with the inner surface in which event some material displacement or deformation takes place during the assembly of the end wall with the housing body. The bores in the end wall may be equiangularly distributed along a circle centered on an axis coinciding with that of an opening for a drive shaft in the end wall and, in the mounting position, with that of a circular section of the inner surface at the open end. A cylindrical projection may be provided at the other end face of the end wall for clamping the end wall in a clamping arrangement of a material-removing machine during the material-removing operation for producing the contact surfaces of the pins.