Blade Removal and Adjustment on Whisper Chippers

Whisper Chippers, originally manufactured by Asplundh and later distributed under various names including Altec, are drum-style wood chippers designed for municipal and arborist use. These machines typically feature a horizontally mounted drum with multiple blades secured by wedges and Allen screws. The engine—often a Ford 300 cu. in. inline-six or a Ford 302 V8—drives the drum via belt and flywheel, delivering high rotational force to shear branches against a fixed anvil.

Unlike feed-assisted chippers, Whisper units rely on blade sharpness and correct clearance to self-feed material. This makes blade condition and adjustment critical to performance.

Challenges in Blade Removal

Operators frequently encounter difficulty removing the blade wedges, even after extracting all Allen screws. The wedge, which clamps the blade against the drum, can become seized due to:

• Hardened sap and debris buildup
• Corrosion from moisture exposure
• Over-tightening during previous installations
• Lack of anti-seize compound on threads

A common solution involves inserting one of the removed bolts into a designated “pop-out” hole in the wedge. Tightening this bolt forces the wedge upward, breaking the bond. This method is more effective than hammering, which risks damaging the drum or misaligning the blade seat.

Blade Adjustment and Clearance

Proper blade-to-anvil clearance is essential for chip quality and feed efficiency. Most operators recommend a gap of:

• 0.030 inches (0.76 mm) for general use
• 0.016 inches (0.41 mm) for precision chipping
• 1/32 inch (0.79 mm) as a practical reference using a hacksaw blade

Too wide a gap results in thin chips and poor feed, requiring manual pushing of branches. Too narrow a gap risks blade contact with the anvil, causing rapid wear or damage.

Adjustment screws, often frozen from age, must be loosened to reposition the blade. Techniques include:

• Applying penetrating oil over several days
• Using heat cautiously to avoid warping the drum
• Employing impact drivers or air hammers
• Replacing stripped Allen heads with new fasteners

One operator reported success after removing and cleaning all blade pockets, then resetting the blades using a hacksaw blade as a gauge. The chipper resumed self-feeding and produced uniform chips.

Sharpening and Blade Sourcing

Blades must be uniformly sharpened and balanced to prevent vibration. Uneven blades can unbalance the drum, leading to bearing wear and shaft damage. Resharpening should maintain the factory bevel and avoid overheating.

Sources for replacement blades include:

• Bandit Industries (reported price: 4 blades for $125 with free shipping)
• Saw and Knife suppliers specializing in forestry tools
• Local machine shops offering custom grinding

Operators should ensure that replacement blades match OEM specifications in length, thickness, and hole spacing.

Drum Bearing Replacement and Flywheel Removal

If drum bearings fail, symptoms include excessive vibration, heat buildup, and shaft discoloration. Replacing bearings involves:

• Removing the belt guard and flywheel
• Using threaded holes in the taper lock to apply pressure
• Heating the flywheel evenly to release the taper lock
• Extracting bearing caps with bolts threaded into removal holes
• Cutting out old bearings if seized, then installing new ones with proper preload

A millwright shared that improper bearing maintenance led to shaft crystallization and eventual breakage—a costly failure that could have been avoided with regular inspection.

Engine RPM and Feed Behavior

Engine speed affects chipper performance. Operators report optimal RPMs between 2,800 and 3,500, depending on engine model and chipper configuration. Higher RPMs improve feed rate but increase wear. Dry wood is harder on blades and may require shorter branch lengths to prevent engine lugging.

One user noted that after proper blade adjustment, his chipper consumed a 6–7 inch log effortlessly, despite lacking a mechanical feeder.

Final Thoughts

Maintaining a Whisper Chipper requires mechanical intuition, patience, and attention to blade setup. Blade removal can be tricky, but using the wedge pop-out method and cleaning the pockets simplifies the process. Correct blade clearance transforms feed behavior, while sharp, balanced blades protect the drum and bearings. With proper care, these legacy machines continue to serve reliably in tree care and municipal operations.