This is a nutcraker that I designed. It consists of two pieces and works just like a skrew. It works pretty good for hazelnuts and walnuts. In order to use for bigger walnuts you should skale it by 120%. You should choose a rather high infill to make the nutcracker stronger so that it does its duty without deforming or breaking. I printed it with 60% infill and it seems to work pretty good.

For the base, part number two, you can use supports depending on how good your printer handles bridges. I tried it both with and without supports and it worked either way. Althought it came out slightly better with supports.