PURPOSE: To obtain complicatedly shaped clock sheath parts with excellent coupling and closing properties in a simple process, by dividing clock sheath parts, which consists of materials difficult to work or are shaped complicatedly, to simple shapes to work them and working them into one body while utilizing the solid-state coupling property of a superplastic metal.

CONSTITUTION: A case 1 formed with a sintered hard alloy, and a rear cover 2 is formed with a stainless steel, for example, SUS316, and a Zn-22Al superplastic foil 6 with 22wt% Al and rest Zn as the standard composition is interposed between the case 1 and the rear cover 2 and is treated with hot hydrostatic pressure at 250°C in 4MPa, and an adhesive 7 is applied to the connection part between the case 1 and the rear cover 2 for the purpose of preventing corrosion.