DIwYatt: Sharpening the Mower Blades

So I noticed while I was mowing that the lawn mower was leaving a path of tall grass. Since getting the mower, I have only changed the oil, changed the air filter, and added gas. So I figured that it was probably time to sharpen the blades.

It was perfect timing, because I had helped with sharpening my father-in-law’s mower blades 3 days before.

Almost all riding mowers will follow this same basic set of instructions.

First, you will need to drop the deck to the lowest position, and then you will remove the deck of the lawn mower in 4 places.

The back of the deck will have a release on either side.

The front of the deck will have a release.

And the final release is to release the belt.

Now after the deck is free, slide it out the side of the mower, and turn it over on its top. If you notice, I looped the belt around the front linkage connector to keep it tight around the pulleys on the deck. Now to remove the blades. This can be dangerous, so make sure to take safety precautions.

Since the blades spin freely, you need to wedge a block of wood between them and the wall of the deck to stop the blades from spinning.

Then, you can use a socket or boxed end of a combination wrench to release the nut/bolt.

There are two ways to go about sharpening blades. If you have a bench grinder, you can put on some gloves and hold the blades against the grinder. I don’t have a bench grinder so I will show you the other method.

The next step is to clamp the blades to hold them for grinding. The best scenario is that you have a bench vise. If not, I guess you could use a C-clamp or vise-grips of some kind to secure the blades to something. Luckily, my brother-in-law gave me a large vise; he got a newer one that swivels (which is a nice feature if you are going to go out and get one).

I wasn’t entirely ready to drill holes in my workbench yet, so I made a makeshift workbench from the left over slab doors from replacing the doors upstairs that we didn’t need for the garden boxes. I put the vise up on the door and drilled the holes out where the mounting bolts needed to go.

After clamping the blades in the vise, I put on my safety glasses and plugged in the angle grinder that I borrowed from my father-in-law.

It should be obvious where the cutting part of the mower blade is, so you take your grinder and grind on the one side until you get rid of the nicks and dings.

After getting the one side ground smooth, take your grinder and knock down any burrs that are on the backside of the blade where you were grinding.

Do this on all four cutting surfaces; and then you are ready to re-assemble.

I have a couple of tips before putting the blades back on. Use some lubricating spray or some kind of oil to lubricate the threads of the bolts that hold on the blades. This will help keep the bolts/nuts from rusting on and release easier the next time you sharpen the blades. The other tip is to use your block, a screwdriver, or an old chisel to scrape the built-up grass from the bottom of the deck. This just helps keep your deck in better condition and keeps your blades from having any unnecessary friction.