TomD
I would not adjust a mouth with a metal scraper. It is perfectly easy to do with a file. In the metalworking field scrapers are used to fit parts down in into the tens (1/10000"), and to create "points" Perfectly flat surfaces will not hold oil, so surfaces are milled or ground flat, then the surface is final fitted by hand, by re-cutting with a scraper, and raising a certain number of point/inch, so that there is a space for oil in addition to the perfect fit.

Scrapers are useful to get into areas like ramps because you can sharpen a file with a grinder in a few seconds, and will not have to spend 200+ on all the floats a production plane maker might want, and they also work on metal.

Bending into files can be dangerous, though I have never hurt myself with a file, in any of the amusing ways that are suggested.