Trimming

Before you can grind the beef, you must first cut it into pieces small enough to fit through a grinder. Arm roasts usually have long, tough tendons along the seams of the meat, as well as thick gristle that must be trimmed and discarded because it's too tough to grind which means it's too tough to chew. If the arm roast meat is on the bone, use a sharp knife to cut as much of the meat away from the bone as you can. After taking the meat off the bone, cut it into cubes 1 inch in diameter or smaller.

Chilling

The arm roast cubes and all grinding equipment should be chilled thoroughly before you try to grind it into burger. For starters, it's next to impossible to push soft, thawed meat through a grinder, especially without it sticking to everything. Most importantly, grinding thawed meat bruises the meat, which causes it to turn brown faster. To prevent this problem, place the meat in a single layer and stick it in the freezer for 15 to 20 minutes until cold and firm. You'll also want to chill a metal bowl to hold the meat while you prepare to grind it, as well as all parts of the grinding equipment that will touch the meat.

Grinding

A basic hand-crank meat grinder easily turns whole chunks of meat into ground burger meat, but there's no need to buy a meat grinder just for this purpose. You can buy a meat grinding attachment for your stand mixer -- your arms will thank you for allowing the machine to do the work. A food processor also works well for breaking down the meat, though the result is technically chopped chuck, rather than ground chuck. Pack the chilled meat cubes in the top of the grinder and use a tamper -- never a finger -- to push it down against the grinding parts. A bowl under the grinding plate catches the beef as it comes out in strands. When using a food processor, work in small batches and pulse the blades to avoid over-processing the meat. You want patties that hold their shape without becoming mush.

Shaping

Handle the meat as little as possible so the burger doesn't become too dense. This can make the difference between a hamburger that is tender and juicy or tough and dry. In other words, the burger doesn't have to be perfectly round and well-packed to taste great. Scoop up about 6 ounces of ground chuck in your hand in a rough ball shape. Flatten it in your palms with one solid squeeze. Hold the burger with your thumb and forefinger in the center of the patty and slowly turn it in your hands while using your other hand to cup and form the edges. Add minimal spices when frying or grilling the burger so you can taste the full flavor of the meat. Never press with a spatula to squeeze out the juices.