Abstract: A process for manufacturing a siamese-type clyinder block which is disclosed herein comprises a blank making step of providing a cylinder block blank in which a sleeve made of a cast iron is cast in each cylinder barrel of a siamese-type barrel made of an aluminum alloy and consisting of a plurality of cylinder barrels connected in series, and a mechanically working or machining step of forming the inner peripheral surface of each sleeve of the cylinder block blank into a true circle. The process is characterized in that the blank making step includes placing highly rigid sleeves each having a thickness set as large as 10% or more of the inner diameter thereof into a siamese-type cylinder barrel molding cavity in a mold and then pouring a molten metal of aluminum alloy under a pressure into the cavity to effect a casting. The sleeve is cast-in as it is at an ambient temperature or in a heated state.

Abstract: A cylindrical split alignment sleeve of ceramic material has an axial slit and is used in an optical fiber connector for connecting optical fibers to each other. In order to establish the strength reliability of the split ceramic alignment sleeve, a predetermined stress is applied to it by a test procedure ensuring no damage to the sleeve. According to the invention, a test load is applied to the inner circumferential surface of the split ceramic alignment sleeve by a loading part which includes stationary and movable members having inclined slidable contact surfaces. The sleeve is applied onto the load part and the movable member is displaced to apply load to the sleeve. The magnitude of load can be detected by deformation of the loading part or by displacement of the movable member.

Abstract: A rotary structure adapted to be used as a spindle unit for a miniature motor or miniature rotor or as a tape guide roller for a VTR. In the structure of the rotary mechanism, instead of a conventional expensive radial ball bearings, a substantially V-shaped groove is formed in the shaft itself so as to hold balls between this groove and the tapered surface or concave spherical ball receiving surface of an outer race provided around the groove.