MechMaxx SG24 PTO Stump Grinder

Introduction

Your new MechMaxx PTO Stump Grinder is designed for quality construction, ease of use, and safe operation. With proper use and care, it is built to provide many years of dependable service. Experience the durability to tackle any job with the ease, portability, and convenience of your new PTO Stump Grinder.

Key features include:

• MAX performance, MAX Value, MAX Support
• Enhanced design features
• Engineered for optimal user experience
• Quality metal parts used instead of plastic
• Robust warranty supporting all products
• Budget-friendly pricing

Specifications

Dimensions

Overall Dimensions

The stump grinder has the following approximate dimensions:

• Front View: 31.5" (802mm) width
• Side View: 27.7" (705mm) height
• Top View: 42.5" (1081mm) width

3-Point Hitch Dimensions

Diagrams illustrate various measurements related to the 3-point hitch attachment points, including distances between pins and mounting points.

Safety

Safety Signs

The rating plate on your machine may display symbols representing important information. Familiarize yourself with these symbols and their meanings:

• DANGER ROTATING KNIVES HAZARD: Symbol depicting rotating blades and a person. Text warns against going under the frame when the rotor is turning or the engine is running, keeping others away, disconnecting power before servicing, and keeping body parts away from moving parts.
• WARNING: Text states the PTO Driveline MUST be measured and cut as per the Owner's Manual to prevent damage to the tractor and implement.
• DANGER ROTATING DRIVELINE: Symbol of a rotating shaft and a person. Text warns that contact can cause death and to keep away, ensuring all guards are in place and drivelines are securely attached.
• DANGER ROTATING BLADES KEEP HANDS AWAY: Symbol of rotating blades with hands.
• WARNING: General safety advice including reading the manual, not allowing riders, operating with guards, using ROPS and seatbelts, stopping the engine before dismounting, checking lights, not allowing children to operate, and cleaning the work area.
• CAUTION GREASE: Symbol of a grease gun. Text advises reading the operator's manual.

General Safety Rules

• Read this manual and all labels on the machine to understand its limitations and potential hazards.
• Be familiar with controls and their proper operation.
• If the unit is loaned, rented, or sold, provide this manual and safety training. The user is responsible for accidents.
• Read and understand all instructions to prevent electric shock, fire, or serious injury.
• Common sense and caution are essential factors not built into the product.
• Adhere to all applicable Federal and State laws and regulations.
• Only trained individuals who have read and understood these instructions should use the stump grinder.
• Inspect the stump grinder and tractor daily and repair any defects.
• Always shut off the tractor engine and remove the key before performing maintenance or repairs.
• Do not disable or remove safety devices.
• Always locate and mark buried wires, cables, and pipelines before grinding.

Personal Safety

• Do not permit children to operate this machine at any time.
• Keep children, pets, and unauthorized persons away from the work area. Shut off the unit if anyone enters the area.
• Stay alert, use common sense, and do not operate when tired, under the influence of drugs, alcohol, or medication.
• Dress properly: avoid loose clothing, dangling objects, or jewelry that can get caught in moving parts. Keep hair and gloves away from moving parts.
• Use appropriate safety apparel: safety goggles or glasses with side shields, face shield if needed, dust mask, nonskid shoes, hardhat, gloves, and hearing protection.
• Do not overreach; maintain proper footing and balance.
• Remove any adjusting keys or wrenches before starting the machine.
• Never conduct maintenance or adjustments while the tractor engine is running. Always shut off the engine, remove the key, and consult the tractor's manual for safe shutdown procedures.
• Never allow passengers on the stump grinder.
• Identify hazards and take preventive steps to avoid accidents.

Thoroughly inspect the work area, keeping it clean and free of debris. Operate on flat, level ground. Never place body parts where they could be endangered by movement during any phase of operation or maintenance. Keep bystanders and pets at least 75 feet away; stop the unit immediately if approached.

Unpacking the Container

The stump grinder is shipped in a protective crate.

• Top Frame Removal: Unfasten the M8 X 20 mm hex bolts from the four bottom corners of the crate to remove the top frame.
• Support Leg Removal: Unfasten the two M10 × 25 mm hex bolts securing both support legs to the bottom crate frame.

Contents Supplied

Your PTO Stump Grinder comes partially assembled and includes:

• 1x SG24 PTO STUMP GRINDER unit
• 1x Chainsaw Holder Assembly
• 1x Deflector Plate
• 1x Manual Tube
• 1x PTO Shaft

Verify all component and hardware quantities are correct before assembly.

To-Scale Hardware

Hardware graphics are provided at 1:1 scale for identification. Place hardware over the images to verify size.

• Hex bolts: M6 X 20mm (2x), M8 X 30mm (3x), M10 X 35mm (2x), M12 X 40mm (4x)
• Hex lock nuts: M6 (2x), M8 (3x), M10 (2x)
• Spring washers: 12 (4x)
• Flat washers: 6 (6x), 8 (6x), 10 (2x), 12 (4x)

Assembly

Top Link Bracket

Loosen the nut on the front side of the back frame to allow the top link bracket to rotate 180°. Orient the bracket as shown. Secure it to the back frame using four (4) M12 X 40 mm hex bolts, M12 flat washers, and Spring washer 12.

Deflector

Assemble the deflector to the flywheel housing using three (3) M8 Hex lock nuts, three (3) M8 X 30mm Hex bolts, and six (6) Flat washer 8.

Chainsaw Holder

Assemble the chainsaw holder to the flywheel housing using four (4) M12 X 40mm Hex bolts, four (4) Flat washer 12, and four (4) Spring washer 12.

Manual Tube

Assemble the manual tube to the back frame using two (2) M10 Hex lock nuts, two (2) M10 X 35mm Hex bolts, and two (2) Flat washer 10. Remove the cap from the manual tube to access the center mounting hole.

Know Your Machine

Identify the main components of the stump grinder:

• Cutting Wheel Shield
• Chainsaw Holder
• Manual Tube
• Deflector
• 3-Point Top Link Pin
• TEETH
• Locking Pins
• Parking Stands

Set-Up Procedures

Trimming the PTO Shaft

The stump grinder is shipped with a slip clutch PTO shaft compatible with most Category 1 tractors. The shaft may require trimming based on your tractor configuration.

Note: The slip clutch end mounts to the stump grinder.

1. Attach the stump grinder to the tractor's 3-point hitch. Do not install the PTO shaft yet.
2. Raise the stump grinder so the tractor's PTO shaft is aligned with the stump grinder's shaft.
3. Measure the distance between the locking grooves on the splined shafts (Dim A).
4. Measure the compressed length of the PTO shaft (Dim B). It should be 34" (862.5 mm).
5. If Dim A is at least 1" (25 mm) longer than Dim B, no trimming is required. Ensure at least 6" (150 mm) of overlap between shaft halves.
6. If Dim B is longer than Dim A, trimming is required. The amount to trim (C) is calculated as: (B-A) + 1 inch = C. Trim this amount from both halves of the PTO shaft safety cover and then from both shafts. This ensures the safety cover remains a few inches from the shaft ends.
7. After trimming, use a file to remove burrs and reassemble the shaft halves, ensuring they telescope freely.

Note: Strongly Recommended for Hydrostatic Tractors.

PTO Shaft Clutch Run-In

This procedure ensures the PTO shaft clutch plates are properly set and should be performed periodically, especially after periods of inactivity, to prevent plates from sticking.

Warning: Entanglement in a rotating driveshaft can cause serious injury or death. Disconnect and lockout power source before adjusting or servicing.

1. Connect the PTO shaft to the stump grinder and tractor. Insert the locking pin on the clutch yoke and tighten the nut.
2. Scribe a line across the exposed edges of the clutch plates with a marker.
3. Loosen all 8 spring tension nuts uniformly until they are flush with the bolt ends.
4. Tighten all 8 nuts to achieve the proper spring height dimensions specified in the table below, using a caliper for accuracy.

After setting all 8 spring heights, the clutch is ready for use.

• Check the clutch during the first hour of use and weekly thereafter. Watch for excessive slippage, burning odor, or smoking.
• Start the tractor and engage the PTO for 2-3 seconds. Disengage, then re-engage for another 2-3 seconds. Shut off the tractor and remove the key. Wait for all components to stop rotating before removing the PTO shaft.
• Inspect the clutch; if the scribed marks have not changed position, the clutch has not slipped. A clutch that has not slipped must be disassembled to separate the plates.

Flywheel Tooth Torquing

Prior to each operation, ensure all 34 teeth are tightened using the torque adapter and a 24 mm socket. Slide the torque adapter over the nut and torque clockwise. Repeat for all four outward-pointing teeth.

Operation

Pre-Start Checklist

Startup

Preparation for Use

• Check for loose teeth or other loose parts.
• Ensure sufficient visibility and maneuverability to approach the stump grinder.
• Remove the stabilizer pin prior to operation.
• Wear an approved dust mask or respirator, following local, state, and federal regulations.
• Thoroughly inspect the unit after shipment. Check all bolts for tightness, remove shipping materials, and inspect tractor and accessory equipment for safety decals. Verify lynch pins are secure. Visually inspect for loose or missing parts or damage.
• Review tractor pre-start instructions. Never bar over the rotor. Keep the machine's weight in mind and never position your body in line with potential impact.

Attach Stump Grinder to Tractor

To prevent injury or damage, place the tractor transmission in "Park". Check the full range of hitch movement for interference or binding. Never position yourself between the tractor and stump grinder. Only experienced and trained operators should use the tractor and stump grinder.

• Remove the leg locking pins, slide the legs up into the tubes, and reinstall the locking pins to secure them.

First Time User Tips

• Ensure the tractor is off and the PTO drive is disengaged before starting.
• Stand to the side of the stump grinder and observe the center point of the cutting wheel. Then sit on the tractor seat and observe the same point again. Familiarize yourself with this view.
• Test all functions in an open area at idle speed to get a feel for the controls.
• Start with a small stump. Make the first pass, then disengage the PTO and check the progress.
• Get off the tractor after each pass to check progress, as the cutting wheel is often obscured from the operator's seat. Practice improves positioning judgment.
• Always turn off the tractor and disengage the PTO drive before getting off the seat and approaching the cutting wheel.

Field Operation

• Safety: Entanglement in a rotating driveshaft can cause serious injury or death. Keep all tractor and driveshaft shields in place. Do not operate without driveshaft guards. Do not wear loose fitting clothing.
• Preventing Unexpected Movement: Park tractor on a level surface, engage the park brake, disengage PTO, shut off the engine, and remove the key.
• Keep bystanders and pets at least 75 feet away. Debris can be thrown from the cutting area. Keep all shields in place.
• Never operate the tractor with other people in the vicinity or allow riders on the tractor.
• Wood Dust Warning: Drilling, sawing, sanding, or machining wood can expose you to wood dust, which is known to the State of California to cause cancer. Avoid inhaling wood dust or use a dust mask.
• Wear an approved dust mask or respirator.
• Attach the stump grinder to the tractor as per the tractor's Operator's Manual.
• Cutting is done on the front side of the cutting wheel.
• If the stump is on a grade, position the tractor lower on the grade with the cutting wheel higher up.
• Approximate cutting times: 20 Hp tractor - 30 minutes, 30 Hp tractor - 20 minutes, 40 Hp tractor - 15 minutes.
• Operation should be smooth. If the grinder jumps or bounces, you are applying too much force, which can damage teeth and the grinder.

Stump Grinding Procedure

• Observe all operating and safety instructions.
• Position the tractor for grinding. Lower the 3-point frame to the ground. Use stabilizer bars, sway chains, or sway blocks to control side movement.
• Ensure the parking stand is fully raised and secured with a locking pin.
• Set tractor brakes or place transmission in "PARK". Raise the cutting wheel and position it to the left side of the stump.
• Right/left-hand reference is determined by standing at the rear of the grinder facing the direction of travel.
• When engaging/disengaging PTO, use low engine speed. Once engaged, raise PTO speed to 540 RPM and maintain for clean, smooth cuts. Do not disengage PTO at full RPM; always bring the tractor engine to idle speed first.
• Note: To avoid clutch damage, the cutter wheel should not contact the stump when engaging the PTO.
• Before moving into position, remove loose debris from the stump and work area that could be thrown.
• Start the wheel on the edge of the stump and use the side hydraulic cylinder for a light cut.
• After the first pass, raise the cutting wheel slightly and use the side control cylinder to move back to the start position.
• The flywheel spins clockwise. The effective cutting area is in the lower-left quadrant.
• Always start grinding from the right side of the stump, moving incrementally left. Grind softwoods (pine, spruce) up to 2" (50 mm) per pass. For hardwoods (oak, ash, birch), limit passes to 1" (25 mm) per pass. If the chassis sways or the grinder vibrates, reduce the depth of cut or feed rate.
• The operator must wear eye protection and stay on the power unit seat.

Incorrect Grinding Procedures

• It is critical not to pull the grinder through the center of a stump or grind from left-to-right, as this induces vibration, sway, and bounce, potentially damaging the machine or teeth.
• Diagrams illustrate incorrect methods: "Pulling Through the Center" and "Grinding Left-to-Right", both marked with red crosses (❌).

Machine Use and Care

• Ensure the operator is familiar with safety precautions and operation techniques.
• Do not force the machine; use it as designed for optimal performance and safety.
• Storing the machine: Store in a dry, secure place, well-covered, and out of reach of children. Inspect for good working condition before storage and before each use.
• Maintenance: Regularly examine the machine's general condition. Adopt a program of conscientious repair and maintenance. If abnormal vibrations or noise occur, turn off the machine immediately and correct the problem.
• Cleaning: Use a pressure washer to clean carbide teeth, avoiding direct high-pressure spray on bearings to prevent water ingress and damage.
• Use only manufacturer-recommended accessories to avoid injury risks.
• Always operate with all safety devices and guards in place and in good working order. Do not modify or disable safety devices.
• Never leave the machine running unattended.
• Use the machine only for grinding stumps as described in this manual.

Maintenance

Proper routine maintenance is critical for operator safety, achieving good results, and prolonging machine life.

• Before cleaning or maintenance, always turn off the tractor engine and disconnect the PTO shaft.
• Inspect for loose nuts and worn cutting teeth before each use. Clean any debris buildup.
• After 2 hours of operation, check for loose nuts and worn teeth; tighten or replace as needed.
• Grease bearings and pivot pins on the main housing as needed. Do not over-grease bearings, as this can blow out seals and cause premature failure. Refer to the GREASING section.
• Periodically inspect PTO shaft clutch plates to ensure they are not seized. Refer to the PTO SHAFT CLUTCH RUN-IN section.

Replacing Teeth

1. Disconnect the PTO shaft from the tractor and place the stump grinder on a flat, level surface.
2. Remove the M16 X 1.5 lock nut (fine thread) from the back of the tooth using a 24 mm wrench or socket.
3. Remove the worn cutting tooth, noting its orientation for correct replacement.
4. Install the replacement tooth and lock nut, torquing to 160 ft-lb (215 N-m).

Greasing

The stump grinder has six (6) grease points: two (2) flywheel bearings, two (2) hinge pins, and two (2) on the PTO shaft. Check and add grease as needed.

Warning: These grease points come pre-greased from the factory. Do not add grease to these points on a new stump grinder. Over-greasing can damage bearing seals.

Grease points are located on:

• Flywheel Shaft Bearings (Underside of Flywheel Housing)
• Right Pivot Hinge
• Left Pivot Hinge
• PTO Shaft: Slip Clutch End
• PTO Shaft: Tractor End

Troubleshooting

Storage

Storing Grinder

• Store grinder in a dry place.
• Clean thoroughly; dirt and wood chips can draw moisture and cause rust.
• Lubricate machine as necessary (See Service and Maintenance section).
• Check cutting teeth condition; replace as necessary.
• Check for loose or missing hardware.
• Paint parts as necessary.
• Store PTO driveshaft off the ground.

Remove from Storage

• Review Operator's manual and check adjustments.
• Lubricate machine (See Service and Maintenance section).
• If parts were replaced, verify they run properly.

Parts Diagram

An exploded view of the stump grinder shows all components with corresponding part numbers for reference.

Parts List

Refer to the following list for part numbers, descriptions, and quantities: