First place: Preparing armored cable
Armored cable has a metallic armor between two cable jackets. To remove the jackets, it is necessary to cut the armor. Specialized tools are available to cut armor, but a standard plumbing tubing cutter can be used with larger-diameter metallic-armored cables for cutting through the outside jacket and armor. The depth of the tubing cutting blade—about 1/8-inch deep—is generally correct for cutting the outer jacket and armor without harming the inner jacket or fibers in a metallic-armored cable.
Cut the armor just like metal tubing, making several revolutions around the cable, tightening the cutters with each revolution. Armored cable has a thin metal layer between two jackets for protection against rodent penetration in direct-burial installation. The outer jacket and armor are generally thin enough that once a small part is removed, the cable rip cord can be used to split the armor and outside jacket for easy removal. The armor is too hard to cut with a normal cable slitter, so a regular plumbing tubing cutter is used.
Santa Monica, Calif.
This is a reader-submitted suggestion and manufacturers would always want you to use the tool they designed for its intended purpose.
Oldie but goodie: Take the edge off
We hooked up a 1,000A, 480V panel with 500 MCM aluminum wire. Instead of doing knockouts, we cut two square holes at the bottom and lined each hole by slitting open ½-inch PVC and sliding it over the sharp edges. The smooth edge protects your hands and prevents wire cuts.