Invention stories are often full of romance, starting with a crazed but-brilliant inventor conjuring up winged contraptions that never quite leave the ground. Then if the thing should leave the ground, there are always bruising confrontations with the realities of a heartless marketplace.

All this was not the case, it appears, with the Chef's Choice knife sharpener, a savvy little electric implement that was seven years in the making and now seems to have taken that leap to merchandising paradise. Stacks of back orders are surely in the short-term future.

The seven years were orderly, too, growing out of inventor Daniel D. Friel's frustrating weekend and proceeding through paper prototypes, then mechanical prototypes, then manufacture and marketing.

Friel was frustrated because he was trying to sharpen some vintage Gerber tooled steel knives, and found the process impossible. He was not a madman careening around behind closed doors; he was an executive with du Pont de Nemours & Co. Inc. (that's Du Pont for short) who thought the world was large enough for sharp kitchen knives. So he invented a knife sharpener and quit his job to xr devote full time to its nurture.

What could possibly be new about a knife sharpener? Friel's invention, now in the process of impressing many of the world's pickiest knife users (chefs), is the first electric knife sharpener that works.

And it works so well that one store representative suggested that the company might want to give away Band-Aids with each unit. People who aren't used to sharp knives will need to be careful.

An expert in possession of the right stone and steel might be able to do as well, but even that is doubtful. And the expert certainly would require more time; the Chef's Choice works on the dullest knife in just a few minutes.

Friel's invention is based on two innovations. One is the magnetic holders that guide the knife into the proper angle for sharpening. The other is the orbiting motion of the abrasive disks in the last two stages of sharpening -- there are three stages to the Chef's Choice -- that hones the edge microscopically smooth.

Horrible as it is to contemplate, even expensive knives sometimes come from the factory less than razor sharp. And it's easier than it might appear to rearrange the fine edge of a sharp knife into a craggy mass of steel.

Inept sharpening is one of the easiest ways to do this. Nonexperts may hold the knife at the wrong angle to the sharpening steel or stone, or they may bang one part of the edge against the stone, creating a nick.

Electric sharpeners are historically the worst -- hesitate a minute against the cone-shaped sharpener and you've got a gouge in your edge. Ceramic sharpeners -- the kind with two ceramic rods set into a wooden base -- may not even contact the edge, depending on how you hold the knife.

This tricky angle problem is what Friel's magnetic holders were designed to eliminate. The magnets draw the knife down into a groove and hold it there at the proper angle. All you do is draw the knife through the groove, from handle to tip, without applying any pressure at all.

The knife is sharpened in three stages, and in cross section you can see (in photographs taken through a microscope) that edges are angled to a point in three increments instead of one or two.

When you're sharpening a knife for the first time it's necessary to go through all three steps; subsequent sharpenings may require only the last two. The third stage is the one that puts the final edge on the blade, an edge that the Edgecraft Corp., Friel's nine-person company, claims is about one micron thick. That's one thousandth of a millimeter, if you're curious.

The Chef's Choice works on any kind of kitchen knife except electric or serrated.

There is no danger in trying to sharpen serrated knives, but you will wear down the serration. The manufacturer says not to try sharpening scissors, hunting knives or pen knives with the machine.

Very hard stainless steel may take longer to sharpen than other alloys or pure carbon steel, but even stainless will only require a minute or two of your time.

The bad news is this machine is a bit expensive -- $79.99 to be exact. You'll have to figure out how much constantly sharp knives are worth to you, but it can be said that the thing sold like hot cakes at a recent convention of cooking professionals.

In Washington, as of this minute, the Chef's Choice is available at China Closet and Kitchen Bazaar stores, Strosnider's Hardware in Bethesda and Chesapeake Knife and Tool Co. in Georgetown.