First Look: Multi Sharp Rotary Mower and Tool Sharpener

We tested the $30 tool sharpener to see if it lives up to its claims.

Middle aged woman mowing her lawn.

Your garden tools can take an absolute battering. My mower certainly cops it – I’ll absentmindedly run over sticks that the dog has left on the lawn, push it over very uneven parts of the garden and hit the odd rock.

These actions blunt the blade and affect my mower’s performance. As the blade dulls, it stops cutting grass and pulls it instead. Not only does the motor work harder, the finish looks bad as well. You can replace blades when needed, but this is wasteful and costs at least $40 a pop.

As a long-term solution, I purchased a Multi Sharp Rotary Mower and Tool Sharpener from Mitre 10 for just over $30. Theoretically, it should be able to keep my lawnmower blade and other garden tools sharp for years to come. It’s a simple drill-bit attachment with a plastic guide and stone top that sharpens the blade at a fixed angle.

It’s not really a one-stop fix

Multi Sharp Rotary Mower and Tool Sharpener photograph.
Multi Sharp Rotary Mower and Tool Sharpener

The sharpener should be a simple tool to use – bung it in the drill and spin it up and down the blade until it’s looking and feeling sharp. Unfortunately, it isn’t that easy. If your blade has great chunks taken out of it, they first need to be filed down, otherwise you waste your time grinding back notches in the blade.

To get the job done properly I needed to tilt my mower up, remove the blade and clamp it to a table so I could easily work on it. I had an old metal file lying about to get rid of the big nicks in the blade. Lining the sharpener up with the blade is a piece of cake, with the plastic guide ensuring I got it right each time. After a minute or so of the sharpener whizzing up and down the blade, I was satisfied with the results. It wasn’t perfect – the finish was a little bit ragged, but that’s more my fault as the blade had been so neglected no amount of filing could repair all the damage. However, it did improve things dramatically and staved of the inevitable blade replacement for at least another year.

While it’s a simple enough job, I needed to take care to make sure the blade was balanced after I sharpened it. If a blade is unbalanced and you use it in your mower, it’ll vibrate all over the show and potentially damage it beyond repair. You can buy inexpensive balancing tools online, but a nail in the wall does the trick as well. To ensure correct balance I made sure to put the same amount of work into each side of the blade before hanging it over the nail. If it dropped to one side, I just gave that side another run with the sharpener before checking the balance again.

You can do the entire job with the file, though it takes a lot longer to achieve the same result, and you need to be careful with the angle you use or the blade will be duller than before.

Why do you need it?

If you already have a benchtop grinder, you won’t need this sharpener. However, if you don’t and you’re looking for an easy way to sharpen your garden tools, it ticks all the right boxes. The angle guide helps prevent you from making mistakes when sharpening, and the fact that you can easily use it on your secateurs and pruners is a real bonus.

What it doesn’t really do is revive an absolutely battered lawnmower blade. That said, if you’re careful with your mowing and avoid rocks and sticks, it’s an easy way to keep your mower cutting well and your lawn looking sharp year after year.

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Wal Marshall
12 Dec 2020
Use a bench grinder

Ive sharpened all manner of mower and tool blades (and drill bits) on a bench grinder for over 50 years. There is a technique to sharpening each type of blade, (see Youtube) but basically the grinder and wheels will pay for themselves many times over.