There are more designs of domestic nutcrackers than you would believe, and more designs of commercial nutcrackers too. However there also are many kinds of nuts and what works for cracking some of them will not work on others. Have you ever tried to crack a strong-shelled macadamia? It can be quite hazardous. Some nuts, like pistacios, crack open when roasted.

If you are talking about nuts imported from the Third World, such as cashews, they often are cracked by hand, with the technique varying from place to place and variety to variety. Close your eyes and try not to think of dirty fingers.

First-world commercial nut-cracking , depending on the kind of nut, is more or less mechanised. The machines vary in detail and in principle. The amount of force used, and the size of nut they are adjusted for generally requires careful calibration. Some actually work by throwing the nut at a hard surface. Some pass the nuts through spaced rollers. I have not yet heard of any that are based on trained squirrels or Hyacinth macaws.

I would find it hard to believe that any of the mechanisms I have seen would work consistently on the likes of strong walnuts, Hickory nuts and so on. They may be reasonably easy to crack, but removing the fiddly bits of shell can be very tricky.

The only machine that I have ever seen was on the Black Sea coast of Turkey used for cracking hazel nuts. Tw o old mill stones were held apart by a spacer, the nuts went down a hole in the middle of the upper stone and the grooves cut in the stones moved the nuts towards the outer edge of the stones. On their way in between the stones the nuts were cracked. Wooden shoots guided the kernels and the shells onto a wire mesh grid that sorted out very small bits of shell, half shells and the kernels into separate wooden bins. It was very simple and worked really well. I assume most other machines have much the same design.