How to Sharpen Mower Deck Blades

A set of three blades taken off a 60 inch mower deck. The top two have yet to be sharpened on the bench grinder.

Summer is nearing an end. Depending on where you live, another month or two will mean you have swapped out the mower deck for a snow blade. If you are a fan of preventative maintenance like we are at OrangeTractorTalks you will check over and service anything your mower deck might need. Part of mower maintenance is either obtaining new blades or sharpening your existing ones – this article will show you how.

New Blades vs. Sharpening
Sharpening your own deck blades is easy and cost effective. A 3-pack of new blades are priced anywhere from $40-70 USD depending on the mower deck. If you have a couple of minutes per blade and a bench grinder you are all set to not only save some money, but also learn a bit more about your mower attachment.

High Lift Blades
Your mower deck may be equipped with high lift baldes. These blades are found on mower decks with mulchers or bag catchers. They have about a 1″ bend in them that causes a vacuum action under the deck. That suction pulls the cut grass into the bag and clears it out of the path of the blade creating a cleaner, finer cut.

A standards vs. a high lift mower blade. Both in need of sharpening.

Inspecting Existing Blades
We will assume that you have taken your mower blades off the underside of the deck and have them in-hand. Blades that have been in use for a season or two will have visible gouges from stone impacts, jagged edges, deformities and possibly rust if you let your mower sit outside during winter or over top of wet or mulched grass.

Focus your attention on the mounting area of the blade. Look for hairline cracks or other signs of blade instability. If you see cracks you run the risk of that blade coming apart when in use – very dangerous and likely to damage your equipment! Skip the sharpening and buy new blades.

Blade Part Numbers
New blades are sold in sets of either 2 or 3. Whenever purchasing new blades, replace them in sets. This is safer bet and makes it easier to track the age and service history of the blades later. Look at mounting area of an existing blade for the part number. Kubota part numbers are 10 digits long.

Part number location for Kubota mower blades (70722-34330 in this case).

How much to Sharpen
You will need to take the blade material down past the deepest gouge in the blade. In addition, you need to makes sure that both ends of the blade are sharpened to the same depth – that is, the blade is balanced. During sharpening, rest the blade’s midpoint on your finger to test for balance.

A stone impact! We need to sharpen this blade to the depth of this gouge.

How to Sharpen
We use a 6″ bench grinder but a hand file will also work if you have the time and patience. Hold the blade at an upward angle and work the blade from side to side. Check the depth and the balance as you go. You do not need to get the edge the blade razor-thin – in fact, it is better if you do not. A very thin cutting surface is more prone to cracking and gouging on small stones.

Long sleeves protect against debris and hot sparks but be careful around the spinning grinder!

Service Department Vic

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