An improved Davenport® multi-spindle automatic screw machine has a tool arm (14) mounted on a shaft (41) for rotational movement relative to a revolving head cap (13). A needle bearing (42, 42) is operatively arranged between the shaft and the revolving head cap. The bearing is radially loaded as said bearing is installed and that the individual needles of same remain elastically deformed by the radial load immediately after said bearing has been installed. The shaft has a hardened surface (52) that is engaged by the needles. The diameter of the shaft hardened surface portion is greater than the diameters of the adjacent shaft portions. Annular recesses (51, 53) extend into the shaft at either end of the hardened portion. These recesses have frusto-conical surfaces (55) that act as ramps to guide insertion of the press-fittable needle bearing into the space between the shaft and the head cap.