METHOD FOR FORMING DRILLED CASTING, AND CASING FOR SCREW COMPRESSOR

摘要

PROBLEM TO BE SOLVED: To improve inexpensiveness and quality without decreasing productivity, by avoiding damage caused to a drill by runout of the working drill for a drilled casting.SOLUTION: A method for forming a drilled casting includes: a casting step of casting a casting 10 with a cast hole 12 including a flat inner wall surface 15a having one side with a second length H2 set by adding a first length H1 in a manufacturing error range of the casting 10 to a diameter D of a drill 17 and arranged in such a manner as to be orthogonal to a rotating shaft P of the drill 17; and a drilling step of drilling a through-hole 13 communicating the inside of the cast hole 12 with the outside of the casting 10 through the flat inner wall surface 15a by the drill 17.