How to Crack Macadamia Nuts

Use a Vise Grip and a Hammer

Gather tools. You can make a makeshift macadamia nutcracker with a vise grip, an iron bar to set the nut against, and a flat hammer. Vise grips are common tools available at any hardware store. If you love macadamia nuts and plan to shell them often, it's worth buying a vise grip for this specific purpose (though you'll probably find other uses for it as well). Be sure the hammer has a flat end, rather than a round one. You'll need to exert force evenly on the nutshells. If you don't have an iron bar, any tough, metal surface will do. Other hard surfaces like marble, glass, concrete or wood could get damaged by the pounding, so make sure you're working over metal.

Grasp the nut in the vise. Lie it up so that the seam of the nut is facing upward, rather than against the inside of the vise. Set the vise to grip it tightly.

Place the gripped nut against the metal bar. Hold the vise handles tightly and make sure you've got a good grip, since you don't want the nut to slip when you bring the hammer down.

Pound the nut with the hammer. Try to hit it square on the seam so that it cracks cleanly. Let the hammer bounce back toward you as the nut cracks open. You may have to try this a couple of times before you learn exactly how much force to exert. Letting the hammer bounce or pull back slightly is important, since it keeps the hammer from smashing the nut inside.

Release the nut from the vise. The shell will fall away, and the intact nut is now ready to be popped into your mouth or used in a recipe.

Use a Hole in a Rock

Find a rock with a hole in it. This method originated in Hawaii, and is still commonly used there to crack into macadamias. The rock provides a hard surface to stabilize the nut. Look for a small hole that's deep enough to hold the nut in place, but shallow enough so that it sticks out over the hole a bit. If you live near volcanic rock, you'll likely find some with holes just the right size. If you don't live near volcanic rock, locate some limestone or shale with natural, small holes in it. Some people have found success using a crack in the sidewalk; be careful, though, since you could damage the sidewalk with this method.

Set the rock in the hole seam-side up. Carefully place it so that the seam is facing up and you'll have a clear shot when you pound the shell open.

Pound the nut with a rock. Any heavy, flat, hard rock should work. Grasp the rock tightly, lift it over your head, then smash it down on the seam of the macadamia nutshell. The shell should pop right open. Let the rock bounce back toward you slightly after you pound it down. If you continue driving it into the shell you'll smash the nut inside. If you have trouble breaking open the shell, experiment with different angles and rocks of different shapes and sizes.

Extract the nut. Take a look at the nut to make sure it doesn't have gravel or other rock particles attached to it. You may want to rinse it off before consuming.

Finished.