Full definition
Parameter evaluating the severity of speed demands on a bearing: n·dm = rotational speed [RPM] × mean bearing diameter [(d+D)/2, mm]. Typical ranges: <150,000 → general use with NLGI 2 grease; 150,000–400,000 → special high-speed grease or oil; >400,000 → oil jet lubrication, P4/P5 precision bearing, polyamide cage or ceramic hybrid. Basis for selecting the lubrication system. ISO 15 standard.