How Does a Stump Grinder Work?

Special Tool for a Special Job

A stump grinder is a specialized tool made especially for getting rid of tree stumps. The machine also goes by the names stump chopper, stump router or stump cutter. It works by chewing up the wood of a stump to particulate matter, making quick work of what would take nature many seasons to do. The machine features a flywheel, or cutting wheel, bristling with teeth especially made for the purpose of grinding up what is left after a tree has been cut down or blown down and hauled off or otherwise disposed of.

Prep Work

Using the grinder demands eye, ear and head protection, along with safety boots and gloves. Grinders weigh about a thousand pounds, so renting a grinder requires a trailer hitch to tow the grinder to the site. The site has to be prepared before the machine can be brought to bear: rocks around the stump must be removed and the stump should be trimmed close to the ground to make the job go faster. The trimming is done via chain saw.

Bringing the Grinder to Bear

Grinders use hydraulics to make maneuvering the cutting wheel manageable. The operator moves a hydraulic lever to lift the cutting wheel so that it can be positioned a few inches above the stump. With the wheel turned on and rapidly rotating, the operator lowers the wheel into the stump a few inches, then moves the wheel back and forth, using the hydraulic lever. As the wheel and teeth move laterally through the wood, they chew up the wood of the stump. When that area is ground away, the operator lifts the wheel, moves the machine forward, lowers the spinning wheel again and grinds up another swath of the trunk. This goes on until the trunk is completely chewed up.

Outcome

Done correctly, the process removes the core of the tree and leaves a hole in the ground that is 4 to 12 inches deep---sometimes more---creating wood chips that can be used as mulch. The tree will not sprout up again from the stump. All that remains is for the hole to be filled in with topsoil and seeded with grass, if desired. Alternatively, the stump chips mixed with dirt can be used to fill in the hole left behind by the grinding process. In cases where the stump is being removed by the grinder (rather than through rotting away) because the tree and stump had an infestation or disease, the wood chips must be properly disposed of.