Patent ID: 8449815

Claim:
A manufacturing method of an oil-impregnated sintered bearing, comprising the steps of: forming a green compact from a raw powder using a forming mold; sintering the green compact to form a bearing body of a porous sintered alloy in which vacancies are included; forming a bearing hole, in which a rotary shaft can be inserted, in the bearing body made of the sintered alloy; and crushing the vacancies opened on an outer peripheral surface of the green compact by pushing out the green compact from the forming mold, wherein, the forming mold comprises a die, a core rod, a lower punch and an upper punch; the core rod is placed coaxially in the die; the lower punch fits between the die and the core rod in such a way that the lower punch is able to move freely upward and downward; the upper punch fits between the die and the core rod in such a way that the upper punch is able to move freely upward and downward and to be detached from the die; a filling part is formed in the forming mold in a space defined by the outer surface of the core rod, the inner peripheral surface of the die, the upper surface of the lower punch, and the lower surface of the upper punch; and a rough part is formed on the inner peripheral surface of the die.