PROCESSING METHOD FOR JOURNAL HOLE OF LARGE CRANK THROW

摘要

A method and a mold device for processing a journal hole of a crank throw, which can reduce an amount of gas cutting operation by preliminarily forming a journal hole through a hobbing process using a mold device with a shape corresponding to the journal hole, reduce an amount of a material to be disused, and can manufacture a crank throw with the same volume as an existing crank throw using a less amount of the material compared with an existing process, are provided. A mold device for processing a journal hole of a crank throw comprises: an upper hobbing mold(110) comprising a first pressing part which is formed in such a conical structure that the first pressing part has a diameter corresponding to a journal hole formed on a crank throw, the diameter of the first pressing part is reduced as it goes from an upper part to a lower part, and the periphery of a lower portion of the first pressing part is formed in a round shape; a lower hobbing mold(120) comprising a second pressing part(122) which is formed in such a conical structure that the second pressing part has a diameter corresponding to the journal hole, the diameter of the second pressing part is reduced as it goes from a lower part to an upper part, and the periphery of an upper portion of the second pressing part is formed in a round shape; a first guide part(130) comprising a pair of guiding blocks(131,132) which are formed at both sides of the upper hobbing mold or the lower hobbing mold to have a distance corresponding to width of the crank throw, and on which guide grooves(133) with a predetermined depth are vertically formed; and a second guide part(140) comprising a pair of inserting blocks(141,142) formed such that the inserting grooves are correspondingly inserted into the guide grooves of the first guide part at both sides of the upper hobbing mold or the lower hobbing mold.