Been down this road a number of times. For the Brits the file is a flat lolly pop shape, On the other side of the pond a disk about 1/2 diameter diameter about 1/4 inch thick with a 1/4 inch neck about an inch long set in a handle. The cutting part is the disk edge having serrations cut from face to face with a triangular file close together. If you want rounded bases on you drop points round the disk edges. You can use tool steel to make them but I always used mild steel and case hardened them, far easier to re sharpen they just went smaller over the years.
I have looked high and low for my set of drop point files but cant find them, and stock making is out for me now, eyesight not so hot.
