Understanding Reel Mower Blades and How They Cut
Unlike rotary mowers that use a high-speed spinning blade to tear grass, a reel lawn mower functions like a pair of scissors. The mower features a cylindrical reel with multiple helical blades that rotate against a stationary horizontal bar known as the bedknife. When properly adjusted, the grass is caught between the reel blade and the bedknife, resulting in a clean, precise shear. This cutting action is why reel mowers are favored for fine turf, but it also means that the interface between the reel and bedknife must be perfectly aligned and sharp.
You will know your blades need sharpening when the mower begins to tear or bruise the grass rather than cutting it cleanly. If you notice ragged, brown tips on your lawn after mowing, or if the mower feels like it is pulling or skipping over grass blades, the edges have likely dulled. Regular maintenance ensures the scissor-like action remains effective and reduces the strain on your mower’s internal components.
Tools and Materials Needed
Before beginning, gather the necessary tools to perform a safe and effective sharpening job. While some minor touch-ups can be done with a hand file, most reel mower maintenance involves a process called backlapping. Essential supplies include:
- Wrenches and screwdrivers for disassembly.
- Lapping compound (a specialized abrasive paste).
- A backlapping crank or drill attachment (if applicable to your model).
- A fine-toothed metal file or a small whetstone for the bedknife.
- Safety gear: heavy-duty work gloves and safety glasses.
- A clean rag and degreaser for blade preparation.
Always prioritize safety by wearing thick gloves to protect your hands from the sharp edges of the reel and bedknife. Safety glasses are also essential to prevent metal shavings or lapping compound from entering your eyes during the process.
Preparing the Mower: Safety and Disassembly
Safety is paramount when working with mower blades. If your mower is gas-powered, always disconnect the spark plug wire to prevent accidental ignition. For battery-powered models, remove the battery pack entirely. Once the power source is disabled, clean the reel and bedknife thoroughly using a degreaser and a stiff brush. Removing grass clippings, dirt, and dried sap is critical; debris can interfere with the lapping compound’s ability to grind the metal surfaces evenly.
Depending on your mower model, you may need to remove the reel assembly from the frame to access the blades comfortably. Consult your owner’s manual for the specific bolt locations. Keep all removed fasteners in a labeled container so they are easily organized for reassembly.
Step-by-Step Sharpening Process
The most common method for sharpening reel mowers at home is backlapping. This process involves applying an abrasive lapping compound to the reel blades and rotating the reel backward against the bedknife. As the reel turns, the compound grinds both the reel blades and the bedknife, creating a perfectly matched, sharp edge.
Apply a thin, even layer of lapping compound to each reel blade. Use a hand crank or a low-speed drill to rotate the reel in reverse. As you turn the reel, you should hear a light grinding sound. If the sound is too harsh, you may be applying too much pressure or using too much compound. Continue rotating until the blades feel uniformly sharp. If you encounter deep nicks or significant wear on the bedknife, you may need to use a fine-toothed metal file to gently smooth the edge before beginning the lapping process.
Reassembly and Adjusting the Cut
After lapping, thoroughly wash away all traces of the lapping compound. Any remaining grit can continue to grind the blades, leading to premature wear. Reinstall the reel and bedknife into the mower frame, ensuring all bolts are tightened to the manufacturer’s suggested specifications.
The most important final step is adjusting the reel-to-bedknife clearance. The blades should be close enough to cut a piece of paper cleanly when fed between the reel and the bedknife, but they should not be pressed so tightly that they generate excessive friction. Use the mower’s adjustment screws to bring the bedknife toward the reel until you achieve this delicate balance. Test the cut on a small patch of grass to ensure the mower shears the blades rather than tearing them.
Ongoing Maintenance, Alternatives, and When to Call a Professional
To extend the life of your blades, keep the underside of the mower clean and avoid mowing over debris like rocks or thick twigs, which can cause nicks. While backlapping is effective for regular maintenance, it cannot fix severely damaged or bent blades. If the reel is out of round, or if the bedknife is warped, professional grinding is necessary. A professional shop has specialized equipment to perform a precision grind that restores the geometry of the reel. If you are uncomfortable performing DIY maintenance, or if your mower continues to perform poorly after sharpening, consult a professional technician to avoid damaging the equipment further.
