The following problems in disc type spheronizer were confirmed through a dynamic analysis for the motion of circulating material with centrifugal, upward and cascading fluxes.
1) Authenticity of the public opinions on the three-dimensional circulation of material premising the outlook of hold up like an annular twisted rope, and the eddy motion flux at longitudinal section of hold up.
2) Correspondence of the analytical result with the experiential recognition concerning the scale up method.

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In our previous paper, we proposed a corresponding Work Index W_{i. c} which is proportional to the Work Index W_i. W_{i. c} can be determined from the zero-order increasing rate constant in a ball mill grinding.
In this paper, we propose an application of W_{i. c} to compare fine grindability in dry and wet grinding. The grinding tests were carried out by using a mill made of alumina with a diameter 144mm and grinding balls of alumina with a diameter 20mm. The feed sample was silica glass with density of 2, 150kg·m^-3 and vickers hardness of 465kgf·mm^-2. In the case of wet grinding, the volume of water added was twice of the feed sample.
The relationship between W_{i. c} and the particle size was studied in dry and wet grinding. As a result, W_{i. c} in wet grinding was smaller than W_{i. c} in dry grinding. It was suggested that W_{i. c} could be useful for evaluating a fine grindability in dry and wet grinding.

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Ti(C, N)-Mo-Ni cermets were made from two different powder mixtures; one was a mixture composed of Ti(C, N), Mo and Ni fine powders commercially available, the other was a mixture of the Mo and/or Ni fine powders mixed with Ti(C, N) and/or (Ti(C, N)-Ni) ultrafine powders produced by arc-plasma method. Relative density of both cermets reached 99.9%, however, the mixture containing the ultrafine powder was able to be sintered well at relatively lower temperatures than that of the commercially available fine powder (s). The grains consisting of hard and soft material phases in the sintered body became finer with an increase in weight ratio of ultrafine powder, resulting in enhanced Vickers hardness of the cermet. On the other hand, fracture toughness of the cermet was lowered when the mixture contained more ultrafine powder.

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