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?