An improved planing machine for performing an operation on the surface of wooden planks or boards is provided. The planing machine includes a base, at least two support columns disposed on the base, and a carriage assembly carrying a cutterhead. The carriage assembly may be mounted on the support columns. At least one of the base and the carriage assembly is movable vertically towards the other of the base and the carriage assembly. In an exemplary embodiment, the planing machine includes a depth stop adjustment mechanism which allows the operator to accurately select a minimum workpiece depth from one or more predetermined depths. In another exemplary embodiment. The planing machine includes a dust exhaust channel for removing dust and wood chips/shaving generated during the planing operation.