NEW YORK – Danger and exhaustion came with the job in the decade Chen Tianyun spent as a restaurant delivery man in Manhattan.

Traffic threatened to squash his scooter like a dumpling. He survived an armed robbery. Most weeks, he toiled 70 hours so he could send money to his family in China.

And for his effort, he said he was paid a salary of $550 per month – about $1.81 per hour.

Live on your tips, his bosses told him.

Stories like Chen’s are a dime a dozen in New York City, where immigrants make up nearly half the work force and employers who ignore labor laws have long been able to count on a complicit silence from laborers thankful for a job.

But lately, many of those arrangements have been threatened by a simmering service- industry rebellion.

In recent years, low-paid workers around the country have filed a growing number of lawsuits seeking thousands of dollars in back wages from bosses they say failed to pay the minimum wage or overtime.

The complaints cover a wide range of industries and workers, from landscapers and warehouse laborers, to shop clerks and construction contractors, but most share a common trait: They involve immigrants who have become bolder about going to court to demand their proper pay, regardless of their legal status.

Some of the business owners being sued insist they treated workers well, and are themselves being taken advantage of by savvy activists and attorneys.

Federal lawsuits alleging violations of the Fair Labor Standards Act have more than doubled nationwide in recent years, rising from 1,854 cases in 2000 to 4,389 in 2006, according to the Administrative Office of the US Courts.

In New York, many of those complaints have come from workers who say that, for years, they worked mostly for tips.

Chen and fellow delivery workers at the Saigon Grill, a small chain of Vietnamese cafes, filed a lawsuit seeking back pay in March. More than a dozen New York restaurants have seen similar claims in the past few months.

Grocery baggers at supermarkets in low-income neighborhoods have filed lawsuits and complaints with state labor officials over the past year, claiming their only pay was handfuls of coins offered by customers that sometimes added up to as little as $250 a week.

Busboys who cleared tables at Chinese buffets across New Jersey have sued claiming daily wages consisted entirely of tips – minus kickbacks to managers of as much as $20 per shift.

One of those workers, Tony Tsai, 30, of Jersey City, said the last straw for the staff at his restaurant in Wayne, N.J., came when the boss threatened to fine every worker $30 for not washing plates thoroughly.

“We couldn’t take it anymore,” he said.

Attorney Michael Weisberg, who represents the Saigon Grill, said every worker at the company was paid at least minimum wage, which in New York is now $4.60 per hour for tipped foodservice workers.

“They make a fortune!” Weisberg said of the delivery men, all of whom were fired after filing their lawsuit, and now picket the restaurant several times a week.

Managers at some of the grocery stores being sued over their treatment of baggers have said the workers weren’t employees at all, and were offering their services to customers on their own time.

It’s not clear that the surge in litigation means there are more violations taking place.

The U.S. Labor Department said the number of wage and hours complaints it received last year actually fell for the second straight year, to 26,256 compared with 31,786 in 2004.

So why the increase in lawsuits?

Labor attorneys said there has been a proliferation over the past six or seven years in the number of lawyers who specialize in wage and overtime disputes, meaning more cases can be handled without government intervention.