Plug cutters, especially those that cut a tapered plug are an interesting exercise in patent shenanigans. As mentioned in this thread, a tapered plug is almost always superior than a straight sided one...the wedge action as the plug is driven down results in a very snug fit. Lee Valley Tools has a patented Snug Plug cutter. As you might imagine, it's been ripped off by many manufacturers. Lest you thing a tapered plug was patented...be aware it's not. The tool design itself is. In the case of the Lee Valley cutter, it has 4 "legs" that outline and then shear the sides off the plug. A quick patent search on "tapered plug cutter" will illustrate many designs...all patented, and resulting in a tapered plug. The idea is to copy the result of the product, and not the product itself. I will say the Lee Valley Snug plug cutters work very well. While you can use them hand held, they (like any similar cutter) will function far better in a drill press.
> During the late 1950's, Warren Jr. renovated the countersink design -- a change that is extensively used today. Originally the flutes of the countersink were straight in design. In the new model the flutes are slightly slanted. This modified the tool from a scraper to a cutter. The design allowed the wood chips to clear, preventing clogging.
