Flat bottomed straight cutter/straight grain milling cutter:

The most common and economical choice. The cutting edge is straight, the bottom edge is flat and the center is cut, making it a standard bottom cleaning tool.

Advantages: Low cost and easy to obtain.

Disadvantages: The chip removal is slightly poor, and the bottom surface smoothness may not be as good as that of a spiral knife.

Flat bottomed spiral milling cutter:

A more advanced option. Spiral cutting edge can bring better chip removal and smoother cutting.

Advantages: Better bottom surface smoothness, longer tool life, especially suitable for deep cavity cleaning.

Disadvantage: The price is relatively expensive.

Flying knife/corn milling cutter (in specific cases):

For very large flat surfaces (such as leveling the entire surface of a board), a flying knife or corn milling cutter equipped with a large reversible blade may be used for efficient "cleaning" operations, following the same principle as bottom cleaning.