Precision Grinding Inc. has nearly completed a nearly $2.5 million expansion into Bessemer.   PGI took advantage of the “slow, steady return” of manufacturing business last year when it bought the 74,800-square-foot warehouse and its 10.21-acre property. Precision will maintain its current operation at a 65,000-square-foot warehouse in the industrial area of Oxmoor Valley, where it was the first tenant more than 50 years ago. “We’re more than doubling our capacity,” PGI’s CEO Miles Cunningham said. “It’s our biggest expansion ever. This is our expansion for now,” he said. “But I’d like to think there are more expansions in the future.”