Turns out there's a US 2008/0250656 A1 patent for a composite knife blade - a knife blade made of two pieces - one containing the area near cutting edge and the other containing the rest of the blade - welded together. This way the cutting edge may be made of steel that's better for cutting but is more brittle and the rest of the blade can be made of stronger steel that isn't that good for cutting. The patent is issued to Kershaw and they are the only company offering such knifes.

I don't get one thing. What's the novelty here? Drill bits are done the same way - the bit tail is made of some crappy steel and the cutting part is made of better cutting steel and they are welded together with friction. This process for manufacturing drill bits has been used for ages so far and the composite knife blade is in fact a variation of that, so IMO it's not a novelty.

How could such a patent be issued? Do I misunderstand how novelty requirement works or is is a USPTO error?

2 Answers 2


Have a look in Public PAIR for this publication number (2008-0250656) and you will find it has not yet been granted - indeed it was rejected and appealed. A very stormy Transaction History. In the Image File Wraqpper you will find the arguments on both sides.


As mentioned by Epicenter, it's not issued yet (i.e. it cannot be legally enforced), just published. An interesting discussion, however, is whether usage of a similar technique in one field/application (drilling) makes it obvious in another (cutting.) Although drilling and cutting are similar at a very, very abstract level, the physics involved are different enough that they may be considered different fields, and that could be used as an argument for non-obviousness.

However, prior art references from other fields have previously been used to reject claims if the technical principles involved were considered similar enough. I heard of a case (no reference handy, unfortunately, and my recollection is hazy) where claims on a method for decelerating an anchor being dropped off a ship, by slowing the pulley, were rejected in light of prior art for braking used by large trucks. Though the fields were quite different (marine engineering vs. heavy automotive engineering) and the applications even more so (anchor sinking in water vs. a truck speeding on land) the mechanical principles involved in both inventions were similar enough to warrant an obviousness-type rejection.

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