A stump planing device 10 comprises a rotatable support shaft 16, and at least two cutting arms 24 extending from the support shaft 16. Each said cutting arm 24 includes a cutter 48 on a cutting-arm body 30 of the cutting arm 24, and an arcuate centring-guide arm 34 at or adjacent to a distal end of the cutting-arm body 30. Each arcuate centring-guide arm 34 defines a constant outer radius along its longitudinal extent and is spaced from a neighbouring arcuate centring-guide arm 34, so as to provide a gap 46 for the passage of cut material. A stump planing system, and earth drill device, a hydraulic machine, and two methods all utilising such a stump planing device 10 are also provided.
