I was looking for that and the I-Quip a while back and I always wondered how functional they really were.......
There are two categories of worms. The auger type is very much like a wood screw, with sharp-edged threads cut into a shank. If the threads are cut so deeply that they extend through the center of the shank, the worm may actually have a hollow center. Auger corkscrew manufacturers claim that their sharp threads help them penetrate corks more easily than round-edge worms. Critics contend that they tend to slice up the center of older corks, ripping out the soft middle of the cork without removing the entire stopper.Worms with rounded edges are usually made by wrapping a very hot steel rod around a form to make a helix. The tip of the helix is sharpened to help it penetrate the cork easily. Some manufacturers pull the tip out of the helix's perimeter and position it in the center of its hollow core. This makes it easy to insert it into the center of the cork. However, the rest of the worm cannot exactly follow the path of the tip, so the center of the cork can be damaged by this type of corkscrew.Some manufacturers of round-edge helixes score one or two shallow grooves into the outer surface of the worm to increase the gripping surface between the worm and the cork.Round-edge corkscrew worms vary in design. They generally have between three and five turns in a helix that is about 2.5 in (6 cm) long. An open pitch—a comparatively wide spacing between turns—is less likely to cause damage to the cork than a tighter spacing. The outer diameter of the worm is usually 0.3-0.4 in (0.8-1 cm).
Nice review.Items like this have an inherent attraction for me since they are so impractical that they come of as really neat and interesting......