Patent ID: 7287572

Claim:
An aluminum base frame which supports a resin shoe in a guide an endless, flexible, traveling transmission medium, the aluminum base frame having a front surface facing in a first direction for supporting engagement with a resin shoe, and a back surface facing in a direction opposite to said first direction, the base frame being die-cast by a method comprising: assembling a die by bringing together first and second enlongated die parts to form a die cavity; pouring molten aluminum into the die cavity, thereby casting the aluminum base frame; and removing said die parts from the aluminum base frame; wherein the first die part has a continuous face against which the front surface of the aluminum base frame is formed, said face being substantially straight in cross-section planes to which the direction of elongation of the die part is perpendicular, thereby avoiding the formation of oppositely pitched drafts on the front surface of the base frame; wherein the base frame has a pivot hole having a interior wall, in the form of a surface of revolution, for receiving a shaft on which the base frame can be pivoted; wherein at least one of the die parts includes a protruding portion having a continuous outer surface in the form of a surface of revolution on which the interior wall of the pivot hole is formed and a tip; and wherein, for any two stations along the length of the protruding portion, the diameter of the station closest to the tip is no greater than the diameter of the outer of the two stations, whereby the interior wall of the pivot hole is cast without oppositely pitched drafts.