How to Sharpen Reel Lawn Mower Blades

The paper check tells you more than any guess. Cut a strip of newspaper about 2 in. wide, feed it between one reel blade and the bed knife, and turn the reel forward by hand. A sharp, well-adjusted reel slices the strip cleanly across its full width. If the paper folds, tears, or gets pushed through uncut, something is wrong, and the next step is finding out what.

Run the check on several blades around the reel, not just one. A single bad blade points to a nick or a bent blade; every blade failing points to adjustment or a dull edge.

The symptoms that send people looking for a sharpener

• Grass tips come out torn and whitish instead of cleanly cut.
• Stragglers stand up after a pass, and the lawn looks streaky.
• The mower is suddenly harder to push than it used to be.
• You hear scraping or rattling as the reel turns.

Poor contact, a dull edge, or damage

A reel that scrapes, drags or fights you is usually set too tight, not dull. A reel that spins freely but will not cut paper has a dull edge and is the lapping candidate. A reel with nicks, waves or a worn bed knife has damage, and that is a shop grind.

A new reel mower is set up and sharpened at the factory and needs nothing at first. This procedure is for the mower that has done a few seasons.

There is no calendar answer. Published guidance runs from every year to every three years for a lightly used manual reel, and the honest rule is simpler: lap when the paper check fails. For a typical home reel mower that lands around every one to two years of normal use, and longer on a small lawn cut often with clean grass.

The range is wide because the wear is not the same for everyone. Lawn size, grass type, whether the mower hits grit and sticks, and how dry the mower is stored all change how fast the edge goes.

Spring is the practical time, before the season starts and while the mower is coming out of storage. One exception belongs here: some reel designs are built to run without blade contact and are specified as needing no sharpening at all, which the last section covers.

Clean the reel and bed knife first with a stiff brush, not a hose. Water left in the reel bearings and on bare steel is exactly what rusts a manual mower.

Then inspect. Run a gloved finger along the bed knife edge, never across it, and look for nicks, rolled edges and rust. Check that the reel spins freely without scraping.

Set the bed knife to the reel first

The target is light, even contact along the full width: enough that the reel shears paper, not so much that it drags. Too little contact tears grass and wears the edge; too much means heat, noise, a hard-to-push mower and uneven wear.

The bed knife or its mounting moves in small increments against the reel. Nudge it, check by feel, run the paper check, and repeat. Small adjustments with a re-check after each one get you there; a big turn overshoots.

Safety before your hands go near the shear point

Wear gloves and eye protection. Pin the reel with a dowel or a broom handle through it, or chock the wheels, so it cannot turn while your fingers are between the blades.

1. Set up. Put the mower on a flat surface, pin the reel or disengage the drive so it cannot spin under power, and chock the wheels. Gloves and glasses on.
2. Get access to the reel shaft. On most manual reel mowers a crank handle attaches to the reel shaft, often after removing a hub cap or a wheel; some kits replace the drive pinion with a crank. Some people drive the reel with a drill on its lowest speed instead, around 100 to 150 rpm, and only in reverse.
3. Apply compound. Brush a lapping or sharpening compound onto each reel blade edge and onto the bed knife edge, end to end. A chip brush or a small paintbrush works.
4. Turn the reel backwards, opposite to the mowing direction, steadily. This is the direction that hones the edge against the bed knife. By hand that is roughly 100 to 150 turns, several minutes of work and up to about ten.
5. Watch and listen for the finish. The compound goes smooth and lighter in color, the sound changes, and the reel turns more freely. That is the signal to stop.
6. Reapply and repeat if the paper check still fails. Two or three rounds is normal for a neglected mower.
7. Wash the compound off completely with water while turning the reel in reverse, then dry it. Grit left on the blades dulls them on the first forward turn.
8. Run the paper check again on several blades. A clean cut across the full width means you are done.
9. Protect the edges. Wipe a light oil or rub wax on the blade and bed knife edges for storage, and keep the mower dry.

Lapping compound is graded by grit number, and the number runs the opposite way from what people expect: a lower number is coarser and removes metal faster, a higher number is finer and polishes.

The consumer standard for a home reel mower is around 120 grit, which is what the common sharpening kits ship with. Coarser grades around 80 are used on some heavier reels. Finer grades such as 180 and 220 are for finishing and polishing, not for restoring an edge.

For a home mower, one grade around 120 is enough. There is no need to chase a progression unless the reel is in good shape and you are only refreshing it.

What lapping actually does is hone the existing edge by wearing the reel and the bed knife against each other with abrasive between them. It does not re-cut the bevel or bring back a worn cylinder.

A file has a narrow job on a reel mower: knocking down a raised burr or a small nick that stops the reel turning freely or leaves a ridge in the cut.

Use a fine, flat, narrow file with long straight strokes perpendicular to the blade, and remove only the raised metal. Do not file the cutting edge itself, because you will change the bevel and make the reel cut worse. If you do touch an edge, match the existing bevel and never create a new angle.

After filing, run the paper check again and re-check the adjustment. A file is not the way to sharpen a reel mower; that is lapping, or a grind.

Give lapping about five minutes. If the paper check still fails after that, stop: the reel needs a grind, a spin grind to restore the cylinder plus a relief grind on the blade edges, which takes shop equipment and a trained hand.

The signs it is a grind job

• Deep nicks in the blades.
• A wavy or rifled wear pattern along the blades.
• A reel that has lost its shape.
• A bed knife worn concave.
• A mower that has run out of adjustment for seasons.

Contact-free reels

Some manual reel mowers are designed so the reel and bed knife never touch in use. These are specified as needing no sharpening, and their maintenance is a periodic gap adjustment between reel and bed knife, not lapping. If your mower's manual describes a gap setting rather than blade contact, follow that manual instead of the lapping steps here.

When to pay a pro, and when to replace

If the reel is nicked or rifled, or the mower is valuable to you, a shop grind is the right call. A DIY lapping kit is the cheapest route and covers the maintenance case, not the restoration case. On a low-cost manual reel mower with a worn-out reel and bed knife, a full grind can approach the price of the mower, so weigh it honestly before you pay.

• Running the reel forward with compound still on it. This is the classic error, and it dulls the edge you just honed.
• Not washing the compound off before mowing.
• Over-tightening the bed knife to make it cut, which brings heat, noise, hard pushing and rifled wear.
• Using an angle grinder, bench grinder or rotary tool on a reel. It destroys the helix and the bevel, and it cannot be undone at home.
• Filing the cutting edge instead of just the burr.
• Skipping the adjustment and lapping a mower that only needed setting up.
• Hosing the mower off and storing it wet. Rust on the bed knife is a sharpness problem.
• Lapping a reel that needed a grind, which costs an hour and still leaves a ragged cut.

Re-check the reel-to-bed-knife contact after the first mowing or two. The bed knife settles against the reel as it runs, and a light touch-up of the adjustment may be needed.

Cut dry grass, at the right height, and do not force the mower through tall growth. Keep the blades and bed knife wiped with a light oil or wax, especially before winter storage, and store the mower dry. Brush off clippings rather than washing them away.

A reel mower that is adjusted, lapped and kept dry holds its cut for seasons.