To provide a fitting method for a main sleeve, by which the damage of a sloping key and the other parts is prevented and the maintenance and checking work can be reduced, by eliminating the looseness between the main sleeve and a frame even if a frame hole is deformed caused by forging load during operating the press, in the case of fixing the main sleeve for supporting an eccentric shaft in the forging press into the frame inserting hole by driving the sloping key.

When the inserting hole 41 on the main sleeve 21 of the frame 3 is deformed with the forging load, the sloping keys 51, 51' are driven into two positions on the supporting surface of the main sleeve at the inner peripheral surface position scarcely displaced among the inner peripheral surface at the lower side of the hole so as to fix the main sleeve to the press frame 3.