【正文】 bonds. Multilayer metal bonds possess high bond hardness and wear resistance. Profiling and sharpening these tools is a plex process, however, on account of their high mechanical strength. Synthetic resin bonds permit a broad scope of adaptation for bonding characteristics. However, these tools also require a sharpening process after dressing. The potential for practical application of vitrified bonds has yet to be fully exploited. In conjunction with suitably designed bodies, new bond developments permit grinding wheel speeds of up to 200 m s1. In parison with other types of bonds, vitrified bonds permit easy dressing while at the same time possess high levels of resistance to wear. In contrast to impermeable resin and metal bonds, the porosity of the vitrified grinding wheel can be adjusted over a broad range by varying the formulation and the manufacturing process. As the structure of vitrified bonded CBN grinding wheels results in a subsequently increased chip space after dressing, the sharpening process is simplified, or can be eliminated in numerous applications. Fig. 3 shows a typical microstructure of a vitrified CBN grinding wheel. The selection of the appropriate grade of vitrified CBN grinding wheel for highspeed grinding is more plicated than for aluminium oxide grinding wheels. Here, the CBN abrasive grain size is dependent on specific metal removal rate, surface roughness C5 requirement, and the equivalent grinding wheel diameter. As a starting point when specifying vitrified CBN wheels, Fig. 4 shows the relationship between CBN abrasive grain size, equivalent diameter, and specific metal removal rate for outside diameter grinding operations. However, the choice of abrasive grain is also dependent on the surface roughness requirement and is restricted by the specific metal removal rate. Table 1 shows the relationship between CBN grain size and their maximum surface roughness and specific metal removal rates. The workpiece material has a significant influence on the type and volume of vitrified bond used in the grinding wheel. Table 2 shows the wheel grade required for a variety of workpiece materials that are based on crankshaft and camshaft grinding operations. C6 The stiffness of the ponent being ground has a significant effect on the workpiece/wheel speed ratio. Fig. 5 demonstrates the relationship between this ratio and the stiffness of the ponent. Steels such as AISI 1050 can be ground in the hardened and the soft state. Hardened 1050 steels are in the range 62177。 when ground. Maximum wheel and work speeds are required in order to reduce equivalent chip thickness. High pressure wheel scrubbers are required in order to prevent the grinding wheel from loading. Grinding wheel specification is based on an abrasive content in the region of 50 vol.% and a bonding content of 20 vol.% using the standard bonding system operating at 120 m s1. Tool steels are very hard and grinding wheels should contain 23 vol.% standard bonding system and vol.% CBN abrasive working at speeds of 60 m s1. Inconel materials are extremely burn sensitive, and limited to wheel speeds of 50 m s1 and have large surface roughness requirements, typically 1 μ m (Ra). These grinding wheels contain porous glass sphere bonding systems with 29 vol.% bond, or 11 vol.% bond content using the standard bonding system. In addition to the need to select the appropriate bonding system for grinding wheels in accordance with the requirements of the application concerned, the strength of the body of the grinding wheel requires optimization with high cutting speeds. In the case of very high cutting speeds, conventional grinding wheel designs involving a rectangular body and a bore often leads to excessive and irregular extensions of the body and cracking of the abrasive coating. In order to eliminate the possibility of highspeed grinding wheels failing, the material and the geometry of the body must be able to cope with very high cutting speeds. A further aim of the body of the grinding wheel must be to reduce the magnitude of centrifugal forces by optimizing the shape of the body of the grinding wheel without impairing operational safety. Excessive stress in the body of the grinding wheel is to be avoided, and the smallest possible extension of the body is tolerated. A reduction in mass is also necessary to move critical natural frequencies of the system in the direction of higher rotational speeds. Developments in highspeed grinding wheel design have focused on redesigning and optimizing the shape of body f