A manufacturer in New Haven is expanding. Continental Diamond Tool has announced plans to create up to 226 jobs over the next four years at its New Haven plant. Officials say the company will invest $5.5 million to expand its 112,000-square-foot facility by an additional 15,000 square feet to increase its manufacturing capacity and R&D labs. To support its growth, the company will also invest in new computer and IT hardware as well as new machinery and equipment. The expansion is expected to be complete by late July. The company, which has 130 full-time employees, plans to hire CNC programmers, skilled CNC operators, diamond product finishers, sales executives and more.