A burr mill, or burr grinder, is a mill used to grind hard, small food products between two revolving abrasive surfaces separated by a distance usually set by the user. When the two surfaces are set far apart, the resulting ground material is coarser, and when the two surfaces are set closer together, the resulting ground material is finer and smaller.
If you grind your teeth and your dentist has given you a night guard for it, this article is for you. The old fashioned method of treating bruxism is to cover the teeth with a night guard to protect them from the strong vertical forces caused by grinding, which causes teeth to crack, break, and, over decades, slowly wear the teeth away to stubs.
In the grinding process, materials are reduced in size by fracturing them. The mechanism of fracture is not fully understood, but in the process, the material is stressed by the action of mechanical moving parts in the grinding machine and initially the stress is absorbed internally by the material as strain energy.