Pressure flaking bone is like biting into a candy apple with false teeth......pretty darn useless, and messy. If you do manage to get a good flake, mount it on a wall as a trophy: you won't see too many in your lifetime.
I've tried percussion on bone too....not pretty. Your dog could probably be trained to chew a better arrowhead.
Grinding is the way to go. Use a dremmel type tool, disc sander, or belt sander. Wear a mask. And warn everyone that the air is about to smell like a crematorium.
If you want to be primitive you can also grind the bone on a rough, flat, stone surface. But this is tedious and the stone loads up quickly with bone dust. Haft the bone fragment onto a stick to get better leverage or use a long bone....then cut the arrowhead off the top (after it is fully shaped).
