PURPOSE: To decrease the number of manufacturing process by installing a wire mesh semicylindrical body provided with mortar finishing gages on its both ends in axial direction, spraying mortar and finishing the surface of the mortar by a scraper placed on the gages.

CONSTITUTION: Semicircular arc-shaped mortar finishing gages 3 and 3 are mounted in a concrete groove 1 on both ends in axial direction. Surfaces to be coated are sprayed with mortar by a mortar spraying nozzle 5. Then, a scraper 6 is placed on the finishing gages 3 and 3 and excessive mortar is scraped off by moving the scraper 6 in the axial direction of a semicylindrical body 2. The finished surface of a casing is thereby formed immediately, decreasing the number of manufacturing process.