Carving a hat brim can be a little tricky when it comes to its thickness in that it needs to look thin and still maintain its strength while being carved thin.  A common approach is to carve the brim as thin as possible while leaving the outer edge having a flat surface that magnifies it appearance as being too thick.  The trick is the chamfer the edge by slicing the top and bottom corners of the flat surface edge into a knife edge appearance.  The hat brim will maintain it strength in thickness while the edge will be narrow giving the appearance of a thin brim.

Study the illustration photo that shows a hat brim in the process of being carved to shape.  The area illustrated in the “B” section shows a flat surface reflective of the thickness of the brim.  Illustration “A” shows the brim chamfered into a knife edge giving the appearance of a thin brim.  Illustration “C” shows the brim thinned at its edge almost with a knife edge chamfer, only a little thicker to give a rustic and ragged edge to the brim.  “A” is the YES, “C” is a MAYBE while the “B” is a NO because the flat edge is not artistically appealing making the hat brim way too thick in appearance.

The photo below will show examples of knife edged hats brims in their finished stage.