PHILADELPHIA -- Over and over, the machines leave their marks on the coin blanks. More than a million times an hour, 26 million times a day, the images of Abraham Lincoln and the Lincoln Memorial are stamped into the zinc-and-copper disks.

Amid a cacophony of thumping, chinking and whirring, the new pennies cascade in sparkling rivers through steel troughs to waiting collection bins for counting, the end of an operation that drones on 24 hours a day, five days a week.

This year, the Philadelphia branch of the U.S. Mint will turn out about 7 billion cents, at least half of the number produced in the nation. The rest will be minted in Denver.

But the lowly penny, so long a part of the nation's history and culture, has come under attack in recent years. Gradually decreasing in purchasing power, the coin has become a nuisance to people who find it multiplying in their pockets and purses, weighing them down. Cents accumulate in jars and pile up on dresser tops -- and take time to count.

"We'd like to get rid of the penny," said Sheri Aguirre, spokeswoman for the National Association of Convenience Stores in Alexandria, which represents 58,000 stores in the nation. "It's too cumbersome and takes more time to hand out change to a customer. We have to be convenience oriented."

Rep. Jimmy Hayes (D-La.) has sponsored a bill to eliminate the penny and round off transactions to the nearest nickel. But the measure -- now in committee -- has so far received a cool reception.

Americans seem attached to the penny for sentimental and practical reasons. Sixty-two percent of those surveyed in a Gallup Poll this year opposed the coin's demise and 77 percent were concerned it would lead to increased prices.

"People want to keep the penny," said Michael Brown, executive director of Americans for Common Cents, a Washington lobbying group that has been battling to retain the penny. "There's no reason to make a change. Whoever heard of nickel loafers?"

The penny is woven into our sayings and phrases, repeated by people without thinking:

"A penny for your thoughts?"

"A penny saved is a penny earned."

"Penny-wise and pound-foolish."

Americans talk about penny-pinchers, about putting in their two cents. They play penny-ante card games, find "lucky" pennies, go to penny arcades, name daughters Penny and earn a pretty penny.

But aside from their place in history, the shiny coins filling bags every day at the U.S. Mint here have practical appeal, according to Americans for Common Cents.

"We need pennies to pay sales tax," said Brown, adding that the Japanese recently instituted such a tax and have seen a marked increase in the use of the yen, Japan's penny. "People also don't like price-rounding because it can cause merchants to raise prices." Brown's group includes members of the zinc industry, coin-collecting organizations and other associations.

During testimony before Congress in June, Raymond E. Lombra, professor of economics at Pennsylvania State University, said that "rounding" would dramatically increase government expenses for such items as federal pension and Social Security benefits.

"Although the direct inflationary impact is likely to be small, the effect in dollar terms on federal government outlays ... could cumulate to a considerable sum," he said, estimating the amount at $1.5 billion over a five-year period.

Besides, penny proponents say, the coin is a good investment. David Karmol, a spokesman for the U.S. Mint in Washington, said that it was produced for less than its face value and that it added about $40 million to federal coffers last year. "The mint," he added, "has taken the position that the penny should not be eliminated."

In fact, Rhod Shaw, chief of staff for Rep. Hayes, said the Louisiana legislator expects the penny to stay -- and his bill in the House of Representatives to fail. But Shaw added that Congress may reconsider the matter by the year 2000, when, he said, the penny will begin costing more than it's worth.

"We thought Congress should take a look at the issue, the value of the penny and its perceived use," Shaw said.

"We hold no animosity toward the coin. But to be honest, I really do believe the penny will no longer be with us. It doesn't make sense to hold something in your hand that costs more to produce than it's worth."

James Benfield, executive director of the Coin Coalition in Washington, said his group had called for the elimination of the cent but had taken a neutral position on the issue two weeks ago to devote its energies to the re-introduction of a dollar coin.

The coalition's members include the National Association of Convenience Stores, members of the copper industry and trade associations.

"We were against the penny because the largest argument against the dollar coin was its weight in pockets," Benfield said. "So we thought if we got rid of the penny, that would mitigate the argument" since the weight of the pennies would be eliminated.

But the Coin Coalition changed its position after running into strong resistance that, Benfield said, threatened to undermine the campaign for a dollar coin.

"We didn't need the baggage," he said. "The penny really does not hurt the cash retailing industry to any great extent."

The Senate is considering a measure to introduce a new $1 coin. The House is reviewing a proposal to eliminate the dollar bill, another monetary institution, and introduce a $1 coin, following Canada's example.

The dollar-eliminating measure has run into resistance from Rep. Silvio O. Conte (R-Mass.), whose district includes a company that produces the paper for the currency. His comments to Congress in May show how heated such fights can become.

"The whole idea is shameful," Conte said. "Imagine taking away the dollar bill -- the symbol of prosperity, the image of our country's greatness, the emblem of American economic might -- and replacing it with a giant penny.

"A giant penny, Mr. Speaker! What a pathetic statement of American decline! Why not make whiffle ball the national pastime or change the Statue of Liberty for a statue of Bozo the Clown while we're at it?"

While the money debates rage on, the mint keeps making pennies in its cavernous, hangar-like facility. The Philadelphia Mint also produces nickels, dimes, quarters and half-dollars.

The cents start out as smooth blanks -- already cut from sheets and edged at a private company. The disks travel to a deep bin called a dumper, which feeds them onto a conveyor belt.

The belt carries the blanks into machines that sift out any with imperfections or damage. The shiny metal disks fall through trays filled with holes onto a conveyor that takes them to the presses.

There, the huge, noisy machines -- equipped with dies, digital counters and lighted panels -- take about a second to stamp the blanks on both sides while workers with earplugs and protective eye gear watch over the process.

"Now they get counted," mint spokesman Tim Grant said as he walked through the facility.

Grant stopped at counters where tens of thousands of pennies, still warm, poured into bags for storage in the mint's vaults, until they're needed.

"I don't see any advantage to getting rid of the penny," said Isaac Lichy, 76, a Brooklyn, N.Y., man who was walking through the mint's gift shop, adjacent to a spot on the self-guided tour that draws people to the mint. "There's nothing to gain."

"I've gotten used to it," added his wife, Laura, 68.

"She ought to be," Isaac quipped. "She's got a ton of them."