to that of the hole the ring 12 fig4 9 is intended to align the device with the axis of the hole at the initial stage of operation of the device when the major part of the latter is still outside the hole the device is aligned due to the fact that the diameter of the ring is equal to that of the hole to make it possible to replace the ring 12 to suit a different diameter of the hole said ring can be detached from the body 9 together with a part of the body and ribs 11 to protect the device against breaking in curved sections of the hole it is preferred that the part of the body carrying the ribs 11 and the ring 12 be connected with the main part of the body 9 by a ball joint 13 fig4 the body 9 of the device can be made hollow in this case it can accommodate a device for additional moistening of the formed casing this device comprises a chamber 14 and a system of channels of which channel 15 fig4 and 6 delivers moistened compressed gas into the chamber 14 and channel 16 discharges the used gaseous medium the walls of the body 9 around the chamber 14 are provided with openings 17 fig4 and 6 which admit the moist gaseous medium to the formed casing 8 the channel 15 is in communication with a source of compressed air the space in the tail portion of the body 9 can accommodate a device for.