Bones, make a punch out of a piece of 5/16ths steel rod, by chucking it up in a drill motor and turning the last 3/16ths or so down with a sharp file. You only need a very small sharp shoulder. Then, knapp a slot in the rear of the flint to strattle the hammer screw. this will shorten your flint, and keep it from walking sideways. This tool will make your flints last longer if you use it to knap them sharp, because it takes off such small flakes.
Hungry Horse