US Patent 9187211 Milling jar with integrated lifters

A milling jar has a jar body and a jar neck. The jar body has an internal surface and an external surface. Ridges with gently sloping slides, called “lifters,” are formed by indenting the surface of the jar wall so that the internal surface projects toward the center of the jar. Because the depressions (on the external surface) and the lifters (on the internal surface) are segmented, portions of the circumference of the jar remain cylindrical. The jar neck has a lid that secures the materials inside the jar when the lid is fastened.