Before this gets any more out of hand, please realize that magnification is not the end all, be all. Unless the surface you are examining is perfectly perpendicular to the scope's line of sight, some areas in the image will be in focus and some will not; but even then there will be a difference from the center to the outer edge of the image. If you see bright reflection off the bevel on one end of the blade and can see the scratches in the bevel on the other end, then there is no chance that the entire blade is in focus.

Even if an image is in focus, resolution will make it appear not to be. High magnification is pointless with inadequate resolution. USB cameras with multi hundred X magnification but with just a few mega pixels cannot provide the resolution to needed to make a sharp image. I'm sorry, but they just cannot.

So here's another re-hash...

Magnification
Resolution and total pixels
Blade angle
Light source angle

They all matter.