Be careful with props... the makers recommend you discard props if they have any damage, and for good reason. The tips of the prop are traveling at around Mach0.8... (12"prop at 15Krpm is 861kph.....) (trivia: the prop tips of almost all propellors travel at a maximum speed of about 850kph... regardless of the prop size - including helicopters etc.)

Anyways, an uneven prop can cause serious vibrations, and the forces during flight are substantial. I am not saying that all "blemished" props should be replaced, just that you should very carefully inspect all damaged props, and err on the side of caution. Personally I would throw away any prop that needs to be sanded to fix it.

There is this thing called dynamic balancing with props. Not only does the weight of the prop have to be symmetrical on each blade for the spinning prop to cause no vibration (statically balanced), but the thrust produced by each blade should be the same, and should be symmetrical as well (dynamically balanced)... sanding one side of the prop to be different (even slightly) from the other will cause a dynamic imbalance, and will cause uneven thrust on your prop which in turn causes vibrations, etc.

So, just be warned that props are precision tools and they have the potential to do the most damage in the hobby as well. Thus, props should be treated with appropriate respect.

gus