of the inner surface with a permeability value reduced in respect to that of the remaining mass the number of reduced permeability areas varying from one to two times the numerical value of the diameter expressed in millimeters application_number US 3956979 A description with reference to fig1 number 1 indicates the shaft rotating in the sense indicated by arrow r 2 is a sintered bush inserted in a seating 3 p indicates the direction of action of the load while the oil flow is indicated by arrows f zone 4 shown by the hatched area is the one wherein the oil sucked in by bush 2 progressively as the pressure increases introduces itself again into the porous surface of the bush itself so that in the area of maximum pressure the lubricant film interposed between shaft 1 and bush 2 is lacking according to the present invention fig2 it is provideed to establish a certain number of reduced permeability areas indicated by 5 symmetrically distributed on the inner surface of bush 2 areas 5 have the intent of preventing the oil penetrating into the porous mass thus allowing the formation of a continuous film of lubricant where shaft 1 34 floats 34 the number of such areas 5 may vary from 1 to 2 times the numerical value of the size of the hole diameter expressed in mm according to the characteristics as a whole of the shaft bearing group such as the possibility of assembling the bearing in the.