Sharpening Lawn Mower Blades

 Photo by Daniel Watson / Unsplash

By Kurt Anderson

Putting a fine edge on your push mower’s blades is an easy task, but there are potential misfires. Here are some tips for when you're sharpening lawn mower blades at the cabin.

A wound created by a sharp, straight-edged blade will heal faster than one caused by a dull, ragged blade. The same holds true for the grass that makes up your cabin’s lawn; it will recover faster from the stress of cutting if your lawn mower has sharp blades.

Here’s a list of the top five things to remember:

1. Disconnect the spark plug. You definitely do not want to nudge the engine’s compression into the power stroke while loosening the blade, which can cause the blade to surge forward. And it’s even possible the mower could start – definitely not something you want to happen while you’re wrist deep in the business end of your machine!

2. Flip the mower over so the side with the carburetor is on top. That way, the carburetor won’t fill with oil, and you’ll avoid the cloud of black smoke and potential spark plug fouling. Of course, if the bugs are bad at the cabin that weekend, the cloud of black smoke could double as a yard fogger …

3. Mark the bottom of the lawn mower blade with paint or permanent marker before you remove it – installing the blade upside down after sharpening is going to result in a mighty poor mowing job.

4. Wedge a two-by-four between the blade and blade housing to keep the blade from spinning when you’re loosening the nut on the end of the shaft. Then, use a long-handled socket on the nut to loosen the blade. A shot of penetrating oil works wonders if the nut does not want to come loose right away.

5. Sharpen the blade from the top side down, using either a flat bastard file or my personal favorite, a belt sander. You don’t need to put a razor’s edge on the blade; “butter knife sharp” is the common mantra for a long-lasting, effective cutting blade.

6. Hang the blade on a nail pounded into a wall to check for balance. If the blade hangs lower on one side, file off a bit more metal until it hangs evenly.

7. Retighten securely; a loose blade can cause serious problems to the mower (and your toes!).

Rewinding the Mower Recoil

I know, I know – it’s not the kind of unwinding you had in mind for a weekend at the cabin. But it happens: You pull back on the mower’s starter, and instead of the reassuring hum of a running internal combustion engine, you’re left with a handful of recoil rope. What do you do when your recoil cord breaks? Well, you can always bring it to a small-engine mechanic, who can often rewind a recoil for a few bucks and 10 minutes of waiting time. 

Absent that option, here’s how to do it yourself.

1. Remove the engine’s recoil cage.

2. Replace the old, broken rope with new cord. It’s best to have some extra cord on hand at the cabin. Be sure to route through the hole in the recoil pulley end, and the recoil handle on the other. Use a double overhand knot to serve as cord block.

3. Manually rotate the recoil pulley to ensure the internal spring isn't broken. If you hear clicking noises, the spring will need to be replaced by your local small-engine mechanic.

4. Use a bent paperclip or barbless fishing hook to pull the cord up from between the recoil cage and pulley, until the recoil handle is tight against the outside of the cage. Then slide the cord into the notch in the pulley.

5. Hold the cord between thumb and forefinger next to the pulley, then use that grip as a “handle” to rotate the pulley counterclockwise 4–5 times.

6. Hold the pulley down with a thumb, then pull the slack cord out by the recoil handle. Once it’s out, gently allow the recoil pulley to wind the cord. The handle should go all the way to the cage. If there’s slack, you will need to pull the cord back out, renotch it, and add another turn or two to the original 4–5 winds in step 5.