As a high school shop project some 60 years ago, I made a knife from an old metal working file. I annealed it in the shop oven, sawed the shape, ground it and then hardened it.
The heat treating was not exactly right and the tip broke off and the teacher would not let me take home a knife with an 8” blade.
It could also be because it was not forged. Forging aligns the grain structure to improve strength. The knife made from the saw blade will be similarly left unforced.
So, not an unmitigated success.
(I also made a crossbow from a car leaf spring, that was so powerful that it pulverized a cinder block. That was the second project that year that I was not allowed to take home. But it worked perfectly and looked great. It was modified from plans from Popular Mechanics. The plans called for mounting a conventional bow to the gun stock. The leaf spring option was my brilliant idea.)