Operating the Stump Grinder

AN EXCERPT FROM TCIA’S “BEST PRACTICES FOR STUMP GRINDER OPERATIONS IN ARBORICULTURE” – CHAPTER SIX.

A stump grinder is a heavy-duty machine designed to cut the wood fibers of a tree stump and buttress roots using immense power from a spinning cutter wheel. The idea is to remove all visible traces of the woody tree parts that protrude from the ground after the tree is cut down. Stump grinders are large and expensive, and it would be unwise to assume that an untrained worker can safely operate one by intuition or “common sense.” A lack of training can put the operator in danger from misuse or poor maintenance.


This is why TCIA created its “Best Practices for Stump Grinder Operations in Arboriculture” manual, to assist in training new operators how to use these machines properly and safely. It is also why we are excerpting a portion of it here.

All photos and graphics taken from Best Practices for Stump Grinder Operations in Arboriculture manual.

Prior to operating the stump grinder, it is essential that you read the operator’s manual for proper use.

Learn how to use the machine and its controls safely. Understand and follow all safety labels.

danger zone

Serious injury or death can result if safety instructions are not followed.

Never leave the controls when the cutting wheel is rotating. Before leaving the machine unattended, the operator must shut down the engine. Ensure that all moving parts have stopped, and that the key is removed and pocketed. If there is no keyed ignition, know and follow the manufacturer’s instructions for securing the equipment.

For example, the battery cable and/or spark-plug wires may be removed to “secure” the machine.

In an emergency, stop the cutting-wheel rotation quickly by gently lowering the cutting wheel into the soil. Know the shut-down procedures shown in the operator’s manual.

Keep onlookers at least 75 feet away when the cutting wheel is rotating. Ensure protective guards are in place near windows, cars and other property.

Do not allow children or untrained persons to operate the machine. Keep all body parts away from moving machine parts.

Begin cutting

Approach the stump on the most level section of ground, facing uphill. This will allow the cutter wheel to swing through its full range of motion.

With the cutter wheel disengaged, take an initial non-cutting pass across the stump surface to make sure the boom will swing across the entire arc of the wheel path and/or width of the stump.

You will need to know the cutting pattern of the machine you are working with.

After the initial pass, keep the cutter wheel suspended so it does not contact the stump or the ground. Engage the clutch to start the wheel rotation. Increase RPMs to full operating capacity and advance the cutter wheel into the wood. Be prepared for machine “kickback” or reactive forces when initially contacting the stump.

Grind the roots first

Begin by grinding the roots. If you save them for last, they will be hidden under the chips and difficult to see. You will waste a lot of time clearing them out.

1. Start on one side about 11/4 inches away. Raise the cutting wheel boom, advance the machine slightly, then lower the wheel another 11/4 inches and sweep the boom to the other side.
2. Continue this method until the stump is reduced to the required depth.
3. Continue sweeping the cutting wheel left and right across the stump until the top level of the stump is all removed. As the cut elongates, slightly reposition the stump grinder to begin cutting a new area. If the stump is wider than the swing of the boom, take a few passes to remove as much of the stump as the limits of the boom’s swing will allow. Then reposition so the boom swing will pass over the stump surface.
4. Do not force the machine to make deeper cuts. This could overload the machine, causing personal injury or damage to the machine. Do not hurry or become complacent while operating the machine. Stay focused on the task and alert for vehicular and pedestrian traffic. Observe the flying debris to ensure it stays contained.

Make small, horizontal cutting passes over the roots. Be aware if they are close to irrigation or structures. You may choose to use the stump grinder to just sever the root then pull it up, or use hand-powered cutting/digging tools to remove roots.

Use only the lower portion of the cutting wheel, below the shaft, for cutting purposes. The most efficient section of the cutter wheel is an 80-degree quadrant at the lower front of the wheel. If it were a clock face, it would be between 3:00 and 5:00.

Do not use the upper portion of the cutting wheel or undercut the stump. Sudden loss of control could result.

Root grinding dulls cutter teeth

Grinding roots requires putting the cutting wheel and teeth into the dirt. Running the wheel in dirt will dull teeth prematurely.

When tracing the path of long surface roots across a yard, make shallow cuts to prevent large chunks breaking off and getting thrown.

Grinding the stump wood

When the roots are finished, position the cutting wheel near the top edge of the stump.

Best Practices for Operating a Stump Grinder

• Read the operator’s manual before use.
• Learn how to use the machine and its controls safely.
• Know how to shut the machine off in an emergency.
• The operator must never leave the controls while the machine is in operation.
• Keep onlookers at least 75 feet away when the cutting wheel is rotating.
• Ensure protective guards are in place near windows, cars and other property.
• Do not allow unqualified people to operate a stump grinder.
• Keep all body parts away from moving machine parts.
• Face the stump grinder uphill when grinding stumps on a slope.
• Do not engage the cutter-wheel clutch if the wheel is contacting the stump or the ground.
• Strong reactive forces or kickback could cause injury or damage.
• Grind the roots first to avoid burying them in the chips.
• Use only the lower, front portion of the cutting wheel (between 3 and 5 o’clock) for cutting.
• Keep the cutting passes on the stump shallow to prevent the engine from stalling.
• Do not advance the cutting wheel into the stump while making a cross sweep.
• Do not hurry or become complacent while operating the machine. Stay focused on the task and alert for vehicular and pedestrian traffic. Observe the flying debris to ensure it stays contained.
• Continuously assess the stump for hidden hazards such as cement, rebar, etc.
• Shut the machine down if it begins to make unusual noises or vibrations.

Start on the side of the stump about 1¼ inches away. Lower the cutter head to the wood and make a smooth, continuous cutting pass across the top edge of the stump. Keep the passes shallow to prevent engine stalling. You don’t have to remove the entire depth of the stump in one pass.

The sharpness of the teeth will help determine how much material you can remove on a pass.

Do not advance the cutting wheel into the stump while making a cross sweep. Damage to the engine and/or cutting teeth will result.

Continuously assess the stump for hidden hazards such as cement, rebar, etc. Keep a shovel nearby to dig out buried hazards.

It is common for the tires of the machine to lift off the ground during operation. When this happens, simply lower the machine back to the ground smoothly. Do not drop or catch it suddenly with the hydraulic controls. Damage to the machine can result.

Unusual noise and movement

If the machine should start making an unusual noise or vibration, shut down the engine, disconnect the spark-plug wires, keeping them away from the spark plugs to prevent accidental starting, wait five minutes, then inspect for damage. Vibration is generally an indicator of trouble.

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