Most new broadheads look wickedly sharp at first glance, and some of them actually are. But a good many aren’t, and no matter which broadheads you have, their cutting edges will need a touch-up after you practice with them or shoot them through an animal (or into the dirt).
With replaceable fixed-blade and mechanical heads, you can just swap the old blades out for new ones. But you can resharpen cut-on-contact fixed blades, as well as replaceable blades that don’t have obvious nicks and burrs.
The basics of sharpening a broadhead are no different than the steps in sharpening a knife: You remove material on each side of a bevel to create a clean, acute, sharp edge. You can use a specialized broadhead sharpener, a stone, or a sharpening stick, the same as you'd use for your knife.
I like a sharp but somewhat rough edge, and the file is perfect for getting that done. No matter the sharpener, the idea is to make smooth, even strokes on both sides of the blade, and decrease the pressure as you work.
One neat trick to ensure symmetrical sharpening is to color in each beveled edge with a permanent marker. This helps you remove the same amount of material on each bevel; simply work the bevels against the sharpener until the marker is gone, and recolor as necessary until the edge is sharp. Once you attain that final edge, you can preserve it against oxidation—the slight rusting that can occur in even a well-protected quiver—by coating the blade with a light application of petroleum jelly or bow wax.