PURPOSE: To obtain a metallic pipe having a groove of high dimensional accuracy over the entire outside peripheral part by using a sand mold which is integrally molded to an annular shape to cast said pipe.
CONSTITUTION: The preliminarily prepd. sand mold 1' which is integrally molded to an annular shape is inserted into and held by a core 3 and the core is set into a master mold, then a molten metal is poured into the mold. Then the groove part formed to the pipe has no flashes at all and since the out of roundness on the inside surface of the annular integral sand mold is approximately perfect, the out of roundness of the pipe is improved and the depth of the groove wall is made uniform over the entire periphery. The pipe having the improved accuracy is thus obtd.
UCHINOMARU OSAMU
KATSUKI HIDEO
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