It doesn't take long to figure out after collecting several catalogs on CD ROM that if these things were online, you wouldn't need a 50-CD changer for the engineering department, or to hire someone to keep the stack updated. One online catalog from WM Berg Inc. (www.wmberg.com), East Rockaway, N.Y., can alleviate the problem. The initial screen asks for a product-part number or one from a competitor. If that is not available, users can select from one of about 29 categories, such as assemblies, bearings, belts, clutches, electromechanical components, and gears. Bearings has 13 categories.