But I have since found that vigorous stirring in the rinse water with the drill and paint stirrer method eliminates almost all of the husk materials, and that subsequent cracking and extraction processes are not messy. Drain off the water and replace with hot water. After a minute drain off water and let surface of nuts dry. When cracked the kernels will not shatter because they have picked up enough moisture to be somewhat flexible. The extracted kernels should be spread out to dry overnight.
Most solid metals are more flexible than black walnut shells.
This type of pre-conditioning is unnecessary if you have a good vise. There are many types of nut crackers. In addition, many good nutmeats will be crushed into uselessness because this method can only be applied to the side of the nut. This is archaic, if not actually barbaric, and does not really produce food, in my opinion. Note that I do not plan to crack the shell at the sides.