Conwict, as I read it, the first response recommended a 45 degree edge, and you did a 50 degree... Not much diff there.
I put the hatchet bit in my post vice, and use a combination file. Like the others, I aim for a 40-50 degree edge, meaning the file makes about a 20-25 degree angle with the bit's centerline. Try to keep to that angle or less, the natural rocking motion of the file in your hands will make the edge somewhat convex, enough for your task. If you will be doing "rough" work with the hatchet, with stone strikes likely, then a less acute edge will serve better, whereas for carving/shaving use, a more acute edge rules.
File side 1 until the wire edge grows on the other side, using the coarse side of the file. File side 2 until it matches, and the wire edge is pushed the other way. Switch to the smooth side of the file, and touch up the now completed edge.
Ultimately, this is an impact tool, and a truely keen edge isn't needed. Files are the way to go. Noone packs sandpaper into the woods.
J