Studer RHU450 and RHU500 While the Studer OB continued to have a strong niche in the market place, Studer continued the development of their products and in 1939 produced the world's first cylindrical grinder with hydraulic table transport. The RHU450 and RHU500 were of greater capacity than the OB and are distinctly modern in appearance with close coupled motor drives for both the wheel-head and work-head. As with current Studer models these machines employed plain bearings in the wheel-head.