The problem with cheap USB microscopes is that they provide plenty of magnification, but insufficient resolution to go with the magnification. The first one I purchased was a Plugable scope with 2 MP resolution. It was not very useful.

Then I purchased a Celestron 5 MP scope
https://www.amazon.com/Celestron-Mic...s&sr=1-23&th=1

It provides sufficient resolution. However, when attempting to view the edge of my blades, I found that the plastic ring that protects the lens prevented me from lowering the scope close enough to see what I wanted to see. Thus, I took the scope head to my belt sander and removed the bottom half of the ring. I probably could have done the same thing with a Dremel tool and cut-off wheel.