Yep, Digging in, or gouging, usually occurs when the flint hits the frizzen too high, and at a very shallow angle. If it hits too low, the usual result is that the frizzen doesn't open. You want the flint to scrape, or "slice " steel from the face of the frizzen, not chip it out by gouging or digging into the face. A 60 Degree Angle of Impact has proven to be an optimum angle for the flint edge to strike the frizzen.
This has to do with using the flint's molecular structure, and its natural angles of fracture to cut the steel, and writing about Colloidal fractures is more than BORING- so I won't. If you REALLY want this information, PT me.