Effectiveness and problems of surface grinding machine with a ultra high speed CBN wheel were experimentally investigated.Diameter of the CBN wheel expands depending on the wheel speed. The value of the wheel expansion is able to be compensated bycalculation. Higher surface speed of the wheel results in lower grinding forces. This tendency is more remarkable when stock removalrate is higher. There exist optimum conditions in the grinding with ultra high speed CBN wheel. Utilizing these results, surface grindingmachines with ultra high speed CBN wheel was newly commercialized.Keywords : Su$ace grinding machine. CBN wheel, High speed grinding, Wheel expansion, Optimum grinding condition,Specijic grinding energy, Grinding force, Grain depth of cut1. IntroductionCBN grinding wheels which have excellent grinding ability aregradually employed in many industrial fields [l]-[4]. In order toutilize the performance of CBN grinding wheels for the efficientproduction, a surface grinding machine with ultra high speedCBN wheel is newly developed.This paper describes about performance of the machine andgrinding conditions for practical use.2. Instruments used for experimentsPhoto 1 shows a surface grinding machine developed. Thismachine is equipped with a high speed and high power spindlemotor. Si3N4 ball bearings and an oil air lubrication system areused for the spindle.