Patent ID: 7562539

Claim:
A method for making high precision film coating on a mold core comprising the following steps: (1) providing a mold jig and a mold core to be received in the mold jig; (2) defining a through hole of a first inner diameter in the mold jig for receiving the mold core therein; (3) forming a rim of a second inner diameter on the inner side of the through hole of the mold jig, the second inner diameter being smaller than the first inner diameter of the through hole; (4) forming a body of a first external diameter and a top portion of a second external diameter in the mold core, the second external diameter being smaller than the first external diameter to define a shoulder between the body and the top portion, the first external diameter being substantially equal to the first inner diameter of the through hole of the mold jig and larger than the second inner diameter of the rim of the mold jig, the second external diameter being substantially equal to or smaller than the second inner diameter of the rim; (5) inserting the mold core into the through hole of the mold jig from a bottom of the mold jig, wherein firstly the top portion, the shoulder and the body of the mold core are successively inserted into the through hole of the first inner diameter from the bottom of the mold jig, and then the top portion of the second external diameter passes through the rim of the second inner diameter, and finally the shoulder of the mold core engages with the rim of the mold jig, the body of the first external diameter being received in the through hole of the first inner diameter, the upper surface of the top portion of the second external diameter being substantially flush with the upper surface of the mold jig, and a groove being defined between the inner side of the through hole of the first inner diameter and the outer side of the top portion of the second external diameter; and (6) coating the mold core to form a side hard film on the outer side surface of the top portion of the second external diameter and a hard film on the upper surface of the top portion of the second external diameter.