River Hills-based private equity firm Blackwell Capital Groupacquired Custom Production Grinding, a precision grinding services company based in Menomonee Falls.CPG provides precision cylindrical grinding, honing and surface grinding of parts for manufacturers and machine shops throughout the Midwest. The company can also manufacture special tooling in order to grind difficult parts such as crankshafts and other eccentric parts.“Custom Production Grinding is well known throughout the Midwest for its incredible ability to adhere to very tight tolerances in part profiles, and in meeting demanding deadlines,” Blackwell Capital Group managing director Steve Balistreri said in a statement. “We are looking forward to building upon that excellence, and to expanding Custom Production Grinding’s geographic reach and breadth of services.”CPG was sold by Robert Marx, the second-generation owner of the business, which his parents launched in 1983.Terms of the deal were not disclosed.CPG's leadership team will remain in place following the acquisition. The company currently employs 30 at its 33,000 square-foot facility in Menomonee Falls at N56 W13500 W. Silver Spring Road.As part of the acquisition, CPG launched a new website and new branding, according to a press release.“Our management team is excited about the acquisition,” CPG president Mark Yogerst said in a statement. “We are proud of what we’ve done here and are honored that Blackwell Capital Group saw the value and potential of the business.”Blackwell Capital Group invests in privately held companies in the Midwest with revenues of $5 million to $50 million. The private equity firm typically purchases businesses that are transitioning from their founders to outside the family, or businesses looking to accelerate their growth.