Toolmaker Black & Decker Corp. said Monday it will buy Pentair Inc.'s tool division for $775 million in cash, nearly doubling its sales of tools to professionals in North America.

Black & Decker, based in Towson, also said second-quarter earnings rose more than 50 percent to $121.6 million ($1.50 a share) as the booming housing market drove sales of tools to professionals and do-it-yourselfers.

The stock of the nation's largest manufacturer of power tools rose $7.17, or almost 12 percent, to $67.49 per share, its largest jump in eight years. Pentair's stock fell 51 cents, to $32.29.

Black & Decker has been acquiring companies as it has cut costs over the past few years. It closed a power tool factory in Easton last year, laying off 750 people, and moved much of the work to Mexico. It also bought Masco Corp.'s Baldwin Hardware and Weiser lock business for $275 million last fall. Profits grew by more than a quarter last year.

Pentair, based in Golden Valley, Minn., said it wanted to focus on its business of making water pumps and treatment equipment.

Black & Decker said Pentair's woodworking equipment, compressors and pressure washers fill out product lines where it has "relatively low market share" and would fit well with its Dewalt line of professional tools.

While Black & Decker is strong in cordless handheld tools, Pentair leads in woodworking and stationary machinery such as table saws and sanders. Pentair's Tools Group makes tools under the brands Porter-Cable, Delta, Oldham Saw and others for the $25 billion-a-year power tool industry. Most of its products are sold to professionals. The tool group had sales of $1.1 billion last year and operating income of $82 million.

Although its stock fell, the deal is good for Pentair, too, said Ned Armstrong, an analyst at Arlington investment bank Friedman, Billings, Ramsey Group Inc.

"The tools were a drag on their overall performance," Armstrong said. "This enables them to focus resources and management time."

Black & Decker said second-quarter revenue rose to $1.3 billion from $1.1 billion a year ago. For the first half, earnings rose to $208.2 million ($2.59) from $119.1 million ($1.52).

The tool business is cyclical, said analyst Bob Goldsborough at Chicago mutual fund manager Ariel Capital Management, which owns 3 million shares of Black & Decker. But toolmakers have profited from the housing boom of the past few years.

"The housing market has been strong, the do-it-yourself market has been strong, and with the low interest rates, people continue to buy," Goldsborough said. "But Black & Decker continues to perform."