Most electric meat grinders aren't designed to grind bones and it is a rare manufacturer who says that their electric grinders will do bones, even their heavy duty commercial models. As you would expect, they need to say this because bones can be very hard on motors and can break the internal gears (especially the cheaper model grinders with plastic gears) or overheat the grinder motor. A manufacturer's warranty might be voided if the grinder is used to grind bones.
However, we have found in our experience that most electric grinders are indeed capable of grinding smaller animal bones and soft bones, like chicken, rabbit, etc. Obviously, the larger and more powerful grinder you get, the more durable it will be and the better for grinding soft bones. If you really need to grind bones, say for making your own pet food, we suggest the highest wattage all-metal grinder you can afford. We have found that the LEM grinders go through soft bones like butter because they have all-metal gears and are very powerful.
We do not recommend grinding beef, deer, pork, or other larger animal bones that are more dense, hard, and thick as these may damage your grinder.
Warning: Meat grinder warranties may be voided if they are used to grind bones. However, we have found that these grinders will go through soft bones (chicken, rabbit, fish, etc.) like butter.