I recently got a Stanley 5 1/2 (type 11) which came with a blade which I believe is made of laminated steel. However, the back of the blade is significantly convex, both horizontally and vertically.
I've already used up an 18-inch strip of sticky-backed 120-grit sandpaper trying to flatten it, and there's a lot more to go before I get it flat all the way out to the corners. My free time is limited and I don't really want to spend the time and effort to keep doing this. I've done it enough times to know that it always takes way longer than one expects.
I'd be willing to buy a new blade, but I can't find one that will fit -- this is an older 5 1/2, with a 2 1/4" blade. At some point Stanley moved to a 2 3/8" blade, and all the modern derivatives use the same width.
Has anyone had success with Paul Sellers' method of hitting the middle of the blade with a mallet to flatten it (or even make it concave)? I tried it but it didn't seem to have any effect, though maybe I'm just not hitting it hard enough.