Macadamia nuts are native to Australia and were introduced to Hawaii in 1881. Delicious and high in nutrients, macadamias are quite expensive due to the difficulty in removing the shell. It requires 300 lb. per square inch to crack the shell and can increase the cost of the nuts by 40 to 85 percent. If you happen to get a bag of unshelled macadamia nuts, there are several ways to attempt to shell them.
Prepare the macadamia nuts for cracking. Boiling the nuts for a couple of minutes helps to soften the shell. Freezing them makes the shell more brittle. Roasting the nuts also makes the shell brittle by decreasing the moisture in the shell.
Try several methods used by some Hawaiian natives, just for fun. One method is to place the macadamia nuts in a large burlap sack and tie the open end. Place the sack on the driveway and drive the car over it. Another method is to find a pot hole in the sidewalk that will hold the bottom half of the nut securely. Then hit the nut with a hammer. Be careful not to hit the sidewalk with the hammer.
Secure the macadamia nut in a pair of vise grips. Lay the nut against an iron bar and hit the nut with a hammer. It might take some trial and error to keep from smashing the nut along with the shell. You can also use a bench vise to open them, although if you have a lot of nuts to open, this method will take a long time.
Buy nutcrackers made especially for opening macadamia nuts. The stainless steel MacBuster, made by Bono Macs of Hawaii, is a hand-held nutcracker. You can order a more expensive tabletop nutcracker from several websites, including Aquaponics, Gold Crown Macadamia Association and MacNuts of Hawaii.