To reduce man-hours of mechanical machining for bolt holes so as to secure the positional accuracy of the holes by forming die casting holes the size of which is a little larger than those of bolt holes provided on the collar part flange attaching side of a cylinder head, and bolt holes for making penetration by applying mechanical working process concentrically to the die casting holes from the bolt seat surface side of the collar part.
A die casting hole 16 is subjected to die casing process, except the minimum fitting length so as to be capable of standing against a force made effective when a piston makes contact with a cylinder head 4 as the result of the maximum extension operation of a hydraulic cylinder, that is, very slightly larger than the size of bolt holes on the flange attaching side 15 of the collar part 10 of the cylinder head 4. The solid part 12 of the collar part 10 is subjected to drill machining via a drilling machine panel from the bolt seat surface side 14 of the collar part 10 as that the bolt hole 17 is made to concentrically penetrate the die casting hole 16. Bolts are inserted in the bolt hole 17 and the die casting hole 16 so that the cylinder head 4 may be tightly connected to the flange. Thus, the positional accuracy of bolt holes can be secured, shortening of working time, reduction of cut chips and removal of cut chips can be improved.
ISONO YUKIHIRO
HIRATA KINJI
HASUO SHINICHI
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