The outer burr is not flat, and the inner may be as well. I would have to get another set of burrs from Taiwan to play around with, or source some others. The grinder is a well made machine, with a bearing in the front to support the motor shaft. Since I have the Tiamo version from OE, one of these is getting gifted to a relative. The one knock on these grinders is the lack of a "child proof" feature. The hopper sits on top of a moving auger that a child could get a finger mangled with the machine running. The bean hopper fit is friction, and could be removed by a curious unsupervised child. If not for that; I would consider bringing a crate of these over for sale.