PURPOSE: To provide a titled device made capable of exchanging a disk guide safely and quickly, by constructing the device to put a disk guide pulled out to the outside together with a journal box on a disk-guide bearer, and to lower it to a prescribed position to turn it horizontally.
CONSTITUTION: For exchanging said disk guide 21, in a case of a piercer equipped with upper and lower piercer rolls 6, 9 and disk guides 21, 21 to pierce a material M; firstly, a disk-guide journal box 15 is pulled out to the outside by the actions of a screw shaft 14 and a balance cylinder 16 to put the disk guide 21 on a main body 31 of a disk-guide bearer 27, and the box 15 is taken out by lowering the bearer 27 to horizontally turn it after drawing out a key 22 of a shaft 17 by a hydraulic cylinder 32 through a link 4. A new disk guide put on the other disk-guide bearer is attached to the shaft 17 of the disk guide by an operation reverse to the operation mentioned above.