Black & Decker Corp., a Maryland company that is one of the nation's biggest producers of power tools and home appliances, yesterday began a surprise $1.8 billion cash bid for American Standard Inc., a leading manufacturer of plumbing, construction, air conditioning and transportation equipment.

If successful, the unsolicited $56-a-share bid could more than double Black & Decker's size, making it the third-largest company, in terms of last year's revenue, in the Washington-Baltimore-Richmond area. Only No. 1 CSX Corp. and Marriott Corp. are bigger.

Black & Decker, which employs about 5,400 people in this region and a total of 21,700 people, had sales of $1.9 billion in the year ending Sept. 27. American Standard, with a work force of 39,000, has annual sales of $3 billion.

Late yesterday, William B. Boyd, chairman and chief executive of New York-based American Standard, said the board would study the offer and make a recommendation to shareholders by Feb. 9.

The acquisition of American Standard would be a big step in Black & Decker's "cut and build" strategy, an aggressive program of reorganization that halted a multimillion-dollar flow of red ink at the Towson company and turned it into a money maker during the past several years.

Black & Decker's goal is to lessen its dependence on power tools by broadening the company's income base through the acquisition of other businesses, such as General Electric's home appliance group, now a part of the Black & Decker fold.

"Much of the management team now in place at Black & Decker came from Beatrice {Cos. Inc.}, which was built on growth through acquisition. These guys have been very successful using that strategy," said Franklin Morton, an analyst who follows Black & Decker for the investment firm of Alex Brown & Sons Inc. in Baltimore.

"Here, again, we have Black & Decker going after a company in a leadership position," said David S. Leibowitz, an analyst with American Securities Corp. in New York. "American Standard is a high-visibility company, a leader in its field. That's the kind of company Black & Decker wants. When Black & Decker goes after something, it's goes after something big," Leibowitz said.

Although American Standard officials seemed initially stunned by the offer, Black & Decker officials and analysts said the company should not have been surprised.

Black & Decker Chairman Nolan B. Archibald expressed that sentiment in a letter yesterday to Boyd.

"I was hopeful that you would meet with me to discuss this combination and was disappointed that you would not even listen to a plan that will serve the best interests of our companies and their constituencies," Archibald wrote.

Because the merits of the buyout offer "deserve consideration, our only alternative is to take our proposal directly to American Standard's stockholders," Archibald said in his letter to Boyd.

Boyd "had to have known that Black & Decker was interested," Morton said. "Black & Decker officials had been trying to contact American Standard through several channels over a period of time, but they were rebuffed."

Black and Decker would still like to negotiate the proposed merger, said Barbara Lucas, spokeswoman for Black & Decker. "The last thing we want this to be is a hostile situation," she said.

But the possibility that American Standard might undertake any of a number of counter-takeover measures, or that Black & Decker might ultimately have to increase its offer, led Standard & Poor's Corp. to review the credit ratings of both companies. Some $150 million in American Standard investment-grade debt and $205 million in similar debt for Black & Decker could be affected if S&P were to lower its ratings on the debt.

Black & Decker officials yesterday said they have received a $750 million commitment from Chase Manhattan Bank to help finance the bid, and they said they are "highly confident" that Chase will be able to obtain additional commitments from a group of banks to increase the takeover funding to $2 billion.

Black & Decker's offer will expire at midnight Feb. 24 unless there is an extension.

American Standard stock jumped $20.87 1/2 to $58.87 1/2 a share in heavy New York Stock Exchange trading yesterday, while Black & Decker dropped 87 1/2 cents to $19.50 a share.

------------ FINANCIAL PROFILE ------------

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American Standard Inc.

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Main Business: Air conditioning products, building products and transportation products.

Employees (12/31/86): 38,900

Headquarters: New York

Stock price: 58 7/8, up 20 7/8

52-week high/low: 55/30 1/2

3RD QUARTER ENDED 9/30/87

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Revenue: $840.1 million

Net income: $31.2 million

Net income per share: 98

YEAR ENDED 12/31/86

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Revenue: $2.99 billion

Net income: $188.4 million

Net income per share: $5.15

Ticker symbol: AST

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Black & Decker Corp.

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Main Business: Power tools, household electrical appliances.

Employees (12/31/86): 20,000

Headquarters: Towson

Stock price: 19 1/2, off 7/8

52-week high/low: 26 1/2/13

3rd quarter ended 12/31/87

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Revenue: $612.3 million

Net income: $31.1 million

Net income per share: 53

Revenue: $1.94 billion

Net income: $55.6 million

Net income per share: 95

Year quarter ended 9/27/87

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Ticker symbol: BDK

------------------------------------------------- SOURCE: American Standard; Black & Decker; Standard and Poor's Corp.