Apex, of Sparks, Md., is a 50-50 joint venture between Danaher Corp. and Cooper Industries plc that makes tools and hardware for industrial and retail customers including the automotive, aerospace, electronics, energy and industrial markets. Formed in 2010, Apex generates about $1.5 billion in annual sales, has more than 8,000 employees, has facilities in 30 countries and sells brands including Crescent wrenches, GearWrench ratchets, Lufkin measurers and Jobox storage units.

Bain managing director Seth Meisel said the firm is committed to "drive the next phase of growth" at Apex.

"We've been impressed with the global platform of market-leading positions that the Apex team have been able to build," Meisel said. "In the market, Apex is known for its long tradition of quality and manufacturing excellence, and portfolio of well-known tools brands."

As part of the deal, Bain said that Apex CEO Steve Breitzka and the rest of the management team will remain with the company. Breitzka in a statement said that Bain's "extensive resources and relevant expertise will help us continue to serve our customers well, strategically grow our market share and create additional career opportunities for our valued associates."

The deal comes ahead of Cooper's planned $12.1 billion sale to Eaton Corp. Cooper makes consumer electric power control and lighting products, and it was unclear whether Cleveland-based Eaton had any interest to be in the tool business.

Washington-based Danaher is a diversified manufacturer that for years was the maker of Craftsman tools sold by Sears Holdings Corp. Danaher said it expects the Apex sale, which should close in the first half of 2013, to generate after-tax net proceeds of about $650 million.

Reports surfaced during the summer that Apex was on the block, with Bain and other private equity firms mentioned as potential buyers. Danaher is an active acquirer but of late has been more focused on higher-margin specialty manufacturing including healthcare diagnostic tools.

Boston-based Bain has received committed financing from Barclays plc, Goldman, Sachs & Co., Morgan Stanley, RBC Capital Markets Corp., Citigroup Inc. and Deutsche Bank Securities Inc.

Barclays' Larry Hamdan and Evan Rothenberg acted as lead M&A adviser to Bain, with RBC Capital also advising.

Kirkland & Ellis LLP's Matthew E. Steinmetz, Neal J. Reenan, Richard J. Campbell, Matthew H. O'Brien, Yaman Shukairy, Michelle Kilkenney and Joshua N. Korff provided legal counsel to Bain and PricewaterhouseCoopers LLP provided accounting advisory services.

Apex was advised by Goldman Sachs and attorneys with Gibson, Dunn & Crutcher LLP.