Lt. Col. Oliver North Jr. told Congress he shredded documents "almost every day" while working for the National Security Council. Well, he wasn't the only one. In this city, shredding is big business.

Millions of dollars are spent on shredders every year in Washington, mostly by the federal government. And private businesses and universities across the country are joining in. "Everybody's trying to keep their things quiet," says Vincent DelVecchio, co-owner of Whitaker Bros. Business Machines in Rockville.

Many office supply stores in Washington sell shredders. One of them, Charles G Stott & Co., sells a line of shredders it calls the "Ambassador" series for small offices. These range in price from $995 to $2,295.

"You can get them in any size," says Stott saleswoman Jane Wayne. "One goes right over a wastebasket and one sits on a stand and you install a plastic bag" to catch the debris.

Whitaker Bros. supplies paper shredders to U.S. government offices the world over. Self-described "deans of the shredding industry," Whitaker Bros. carries 100 shredder models, ranging in price from $150 to $40,000.

On display in the company's office is a relic from shredding history: the "Shredmaster." This is the "Watergate shredder," sold to the Committee to Re-Elect the President in 1972 and used to destroy many incriminating documents in its day. Whitaker Bros. bought the machine back from CREEP as memorabilia.

According to DelVecchio, there are basically two types of shredders: those that strip cut and those that cross cut.

The strip-cut shredder slices a piece of paper into 34 straight strips of paper. This is used for employe personnel folders and other bookkeeping and accounting records. Strip-cutting records makes it difficult -- but not impossible -- for unwanted eyes to get at documents.

"There have been cases of strip-cut documents being pasted together," says DelVecchio.

Cross-cut shredders cut paper down to exacting government specifications. They can "take a piece of paper and cut it into 7,500 pieces ... about the size of a closed staple," says DelVecchio.

North used an "Intimus" shredder, Model OO7-S, the type the White House buys for its voluminous shredding needs. It can shred 60 feet of paper a minute, or about 75 pounds an hour, through its 13 1/2-inch-wide mouth.

Intimus is the "Cadillac of the {shredding} industry," says DelVecchio. The OO7-S sells to the General Services Administration for about $4,400. The Intimus 580E, the top of the line, costs $40,000, but earns its keep. The machine features conveyor-belt document feeding.

"Drop a 3-inch loose-leaf binder filled with paper on it and it will go through," says DelVecchio.

Monster machines such as the 580E and the famous Michael Business Machines "Destroy It" shredder are used for other things besides grinding up yesterday's intelligence. Dead-letter departments at post offices use them for mass mincing of unclaimed mail and confiscated pornography. The Federal Reserve uses such shredders to make mulch of paper money that is being taken out of circulation.

A hot item on the shredder market in recent years is the "Piranha," a small machine that sells for around $600. The Piranha fits on top of a wastebasket, where it is fed through a three-inch opening. DelVecchio calls this machine "a novelty." Consumers are beginning to steer away from such trendy items as they "become educated about their shredding needs," DelVecchio says.

The General Services Administration says the government spent $6 million on shredders in 1984, the latest year for which budget figures are available. DelVecchio, however, says of this figure: "It's low."

DelVecchio estimates that the government buys "several thousand" shredders every year. Whitaker Bros. makes up half of that, he says.

Federal shredding is just the tip of the iceberg. Other institutions, says DelVecchio, are beginning to see the need for shredders.

Increasingly, people in creative or sensitive jobs in business and academia are finding that competitors don't have to strain themselves to "steal" from them. They can pluck ideas freely "right out of their trash cans. That's how Hitachi got secrets from IBM," says DelVecchio.

The private sector currently spends $60 million a year on shredders in the United States, says DelVecchio.