Leonard Warnes was facing yet another layoff from his job at a Scranton, Pa., steel mill when he was hired to work at a newly opened Mack Trucks plant here in 1962.

A decade later John L. Warnes gladly followed in his father's footsteps, taking his place on an assembly line that churns out engines and transmissions for Mack's renowned heavy duty trucks.

But after 13 years on the line, John Warnes is planning to take a job at slightly less pay with the D.C. National Guard following an announcement by Mack that it was laying off about 1,000 people in Hagerstown. It is also closing a Pennsylvania plant that uses parts made in Hagerstown and relocating it in South Carolina. The closings have hit this city of 34,000 like a death in the family.

Among many of Mack's blue-collar workers, the layoffs and plant closing threaten to scatter hundreds of relatives -- fathers, sons, brothers and daughters -- who have been hired to work there largely because of family connections, they said.

The new job for Warnes will force him to leave behind a lifetime of friends and family. "It's really a hard job to walk away from. The life style that Mack provides has been very good. But I'm really not willing to risk the future of my family anymore," he said.

The loss of Mack threatens to end a way of life that has become the envy of workers in this Western Maryland industrial town. Mack pays the highest wages in the region, averaging $14 an hour for blue-collar jobs and $23 an hour when fringe benefits are included, according to company figures.

"Obviously this will have a major, tremendous impact on the families involved," said Hagerstown Mayor Steve Sager.

Mack spokesman William McCullough said the company has never had a formal policy to hire relatives, but he acknowledged that "many, many family members are working together within the total corporation."

Local officials are quick to point out that Mack's decision to move is not final. The loss of 1,000 workers, they add, will hurt but will not ruin the Washington County economy, which is supported by 52,000 jobs.

The county unemployment rate is about 6.7 percent, compared with 19.1 percent in January 1983 and 13.3 percent in 1984 when the brunt of 1,000 layoffs was felt at the local Fairchild aircraft plant, which closed most of its operation in 1983.

The planned Mack layoffs here follow difficult negotiations between the company and the union. Pressed by competition from foreign manufacturers, the company wanted workers to accept a $3.85-an-hour cut in wages and benefits and a lengthy salary freeze to shave $35 million a year off production costs.

The United Auto Workers, which represents most blue-collar workers at Mack, made a counterproposal that UAW officials claimed would save $90 million a year without wage concessions.

In the wake of the company's decision to build the new South Carolina factory and to contract with independent companies to make most of the parts produced in Hagerstown, workers said they felt betrayed by the company and ignored by the union. The company, they said, failed to negotiate in good faith, while the union handled the crisis out of UAW headquarters in Detroit without consulting them.

UAW President Owen Bieber flew to Hagerstown last Friday and made another proposal that included wage concessions in an effort to restart negotiations. The company rejected the proposal on Monday.

The impasse in talks has left those who tend the drill presses, lathes and milling machines inside Mack's sprawling factory to ponder an uncertain future.

"A lot of people are right on the edge out here," said Richard T. Brunner, 34, a 12-year Mack veteran. "We're just like pawns on the chessboard."

When Mack located in Hagerstown 25 years ago, it was like a gift from heaven, according to longtime workers. The plant offered steady work at good wages at a time when Fairchild Industries, then the area's largest employer, was in the throes of a major layoff. Over the years, children have followed parents into the plant, lured by the promise of high wages and a solidly middle-class life style.

The company's lavish summer picnics often doubled as family reunions. A private swim club known as Northwood, a low-cost alternative to Hagerstown's only country club, has become almost the exclusive domain of Mack's middle managers.

Even unskilled workers enjoy a life style considerably above their counterparts in other local industries.

"Mack is as good a job as any place around. We've had a good life," said Paul B. Yetter, 45, who was hired in 1962. Yetter, whose cousin works at Mack, is putting one of his three children through college, the first in his family to attend.

Yetter, who vacations every year in Canada, and older workers like him are the most concerned about their jobs. "At my age, I don't know whether I can be trained for something else," he said.

Frank Davies, 66, who also was hired in 1962, has three sons and a stepson working at the factory. Two are laid off and a third is only "six (persons) from the door."

"They're hoping to get back, but they do have skills to do other things," he said. "This is happening everywhere, even with the airlines. I believe in a few more months things will straighten out."

Such optimism, however, is not shared by everyone. "This has done irreparable damage to a lot of people out here already," countered Brunner, who complained about the lack of job security at Mack.

In 12 years there, Brunner said, he has been laid off repeatedly, including stretches that lasted 13 months and 27 months before he was rehired.

The alternatives in Hagerstown are considerably less attractive than the Mack jobs. Of the 29 companies that have recently located in the area, 27 were nonunion and pay blue-collar workers from $4 to $7 an hour, said Leroy R. Burtner, who heads Washington County's economic development efforts.

"It's possible to live up here on that kind of salary," asserted Hagerstown Mayor Sager. "What they may not have is a second home, a mobile home and a boat."

Dale Findley, 34, who worked at the Mack plant with his father and brother, said the transition to another industry could be difficult. "As long as other companies know you work at Mack Truck, they won't think about hiring you because they know you'll always go back," said Findley.

A skilled sheet-metal worker and auto mechanic, Findley, a father of three, said he has been turned down for jobs he knew he was qualified for. "It doesn't matter if you're willing to take $3 an hour. That's just the way they play the game."