Here’s one manufacturer that’s doing something surprising: not leaving Seattle. Instead, Machinists Inc., which fabricates parts and tooling for the aerospace, transportation and marine markets, is expanding with a seventh building. The new 20,000-square-foot building, when fully outfitted, will increase the company's footprint to 115,000 square feet, said Jeff Tomson, head of business development for the company. It will also provide room for a growing work force, which increased by about…