How to Sharpen a Reel Lawn Mower Blade Easily
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How do you sharpen a reel lawn mower blade? The usual method is backlapping: you brush a sharpening compound onto the reel and then turn the reel so the blades grind against each other until the edges are smooth. The steps are simple, but the work is done close to moving metal, so the safety steps come first. This guide explains the method described in a reel mower sharpening guide, notes what the University of California’s pest management program says about how often to sharpen, and points out where a professional shop is the better choice.
Quick answer
- Disable the mower first and keep your fingers clear of the blades at all times.
- Use a backlapping kit: brush sharpening compound onto the reel blades, then crank the reel backward so the blades grind together.
- Finish with a light coat of oil to help prevent rust.
- For reel mowers, the UC IPM guidance is to sharpen about every two years, and a professional shop is the preferred option.
Why a reel blade goes dull
A reel mower cuts by a scissor action between the spinning reel blades and a fixed bed knife. Each blade must meet the bed knife with a clean edge. When the edges round over, the mower tears the grass instead of cutting it. The University of California’s Statewide Integrated Pest Management Program notes that dull blades leave a ragged appearance on grass, and that damaged grass can be more prone to disease. That is why a reel mower should be kept sharp, even if it still seems to cut.
A rotary mower is different. The same UC IPM page notes that rotary blades are often easier to replace than to sharpen, and that many new models include a spare blade. This guide is about the reel style, so the steps below apply to a reel mower only.
How often to sharpen
The UC IPM page recommends sharpening reel mower blades about every two years. Most homeowners will not need to sharpen more often than that, unless the blades were damaged, the mower has been used on rough ground, or the grass cut looks ragged. A reel mower that leaves brown tips or pulls the grass is a sign that the blades or the bed knife need attention.
Frequent sharpening does not replace proper adjustment. The same guide notes that a large share of mowing problems can be fixed by properly spacing the blades. Check the spacing before you assume the blades are the only problem.
What you need
- A backlapping sharpening kit with sharpening compound and a handle.
- A paint brush for applying compound to the blades.
- Optional: an electric drill with a suitable attachment, for faster cranking.
- Optional: wooden chock blocks, if the mower has no arresting gears.
- A light coat of low-acidity vegetable oil for after sharpening.
The optional drill can speed up the work, but it also makes the reel turn faster, so keep your hands clear and control the speed. Many people choose to crank by hand for a slower, more controlled grind.
Step 1: Make the mower safe
Disable the mower before you start. If the blade is not detachable, pin it so it cannot rotate. Keep your fingers clear of the blades at all times. Watch your knuckles, because a small area of force can cause a cut, and finger guards can help.
If the mower has no arresting gears, place chock blocks between the blades to stop the reel from turning. Check the blocks are firm before you apply pressure to the handle. Work on a flat, stable surface so the mower will not move while you crank.
Step 2: Fit the handle
Attach the handle to the driving gear under the hub cap. The handle is what turns the reel. Make sure it seats fully and turns freely before you add compound, so you can feel any stiff spots in the drive.
Step 3: Apply the compound
Brush sharpening compound onto all of the reel blades. Cover each blade evenly, because the compound is what does the grinding. Do not over-apply. A thin, even coat is easier to control than a thick one that drips onto the ground or the bed knife.
Step 4: Crank the reel backward
Crank the mower backward so the blades grind against each other to a smooth edge. Reversing the reel reduces blade wear, according to the reel mower guide used for these steps. Turn at a steady, controlled speed. Stop every so often to check the blade edges, and to clean off any compound that has built up.
If you use a drill for speed, fit the proper attachment and keep the drill speed low. A drill turning the reel fast can fling compound and make the work harder to control.
Step 5: Finish and oil
When the edges are smooth, remove the compound and the handle, and wipe the reel clean. Apply a light coat of oil to prevent rust, using low-acidity vegetable oil as the guide suggests. Store the mower dry, with the reel protected from moisture.
Bed knife adjustment
Sharpening the reel does not fix the bed knife. The reel guide used here does not give steps for adjusting the bed knife. It says that most mowing problems can be fixed by properly spacing the blades, so check your mower’s manual for the spacing and adjustment procedure. Do not change the spacing without the manual, because the wrong spacing can prevent the reel from cutting cleanly.
When to use a professional shop
The UC IPM page says a professional mower shop is the preferred option for reel blades, though do-it-yourself kits are sometimes sold at lawn and garden centers. A shop is a good choice if the blades are badly damaged, bent or chipped, if the reel is hard to turn after sharpening, or if the mower has no manual to guide the spacing. The shop can also check the bed knife, which this guide does not cover in detail.
Common mistakes
- Working on the mower with the blade free to turn. Disable it or pin it first.
- Skipping the oil. A light coat helps prevent rust after sharpening.
- Sharpening too often. The UC IPM guidance is about every two years for reel blades.
- Ignoring the bed knife and the spacing. A sharp reel will not cut cleanly if the spacing is wrong.
- Using a drill at high speed. Control the speed so the compound stays on the blades.
FAQ
Can I sharpen a reel mower blade without a kit?
The reel guide used here describes backlapping with a sharpening compound and a handle. A proper backlapping kit includes these parts. Without one, the steps are hard to follow safely.
Why should the reel turn backward?
According to the reel mower guide, cranking backward reduces blade wear while the blades grind together.
Do I need to oil the blades after sharpening?
Yes, the guide recommends a light coat of low-acidity vegetable oil to prevent rust.
How often should I sharpen a reel blade?
The UC IPM page recommends about every two years for reel mower blades.
Is a professional shop better?
The UC IPM page calls a professional mower shop the preferred option for reel blades.
What if the cut still looks ragged after sharpening?
Check the bed knife spacing against your mower’s manual, because the blades alone may not fix the cut.
Bottom line
To sharpen a reel lawn mower blade, make the mower safe, brush on compound, crank the reel backward, and finish with oil. For most homeowners, sharpening about every two years is enough. If the blades are badly damaged or the spacing is unclear, a professional shop is the better choice.
