Assembly method and assembly apparatus for cross shaft universal joint

An assembly method of a cross shaft universal joint in which a pair of arms of a yoke are backed up from inside in an axial direction by a pair of backup jigs, and cup bearings are press-fitted from outside in the axial direction between bearing holes of the arms and a cross shaft inserted in the bearing holes, the assembly method comprising:

• expanding each of the arms outward in the axial direction by each of the backup jigs;
• press-fitting each of the cup bearings from the outside in the axial direction and caulking each of the cup bearings, with respect to each of the arms in an expanded state;
• releasing an expansion of each of the arms by each of the backup jigs after press-fitting and caulking each of the cup bearings;
• a first expansion of expanding each of the arms to a first expanded state;
• a first press-fitting of press-fitting each of the cup bearings into each of the arms in the first expanded state;
• a second expansion of further expanding each of the arms to a second expanded state after press-fitting each of the cup bearings;
• and
• caulking each of the arms in the second expanded state,
• wherein a distance between the arms in the second expanded state is larger than a distance between the arms in the first expanded state.