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How to sharpen a lawnmower blade with a Dremel, step by step

If you notice that your lawnmower is leaving uncut grass areas, you intuitively know that the problem lies with the blades. They might have gotten dull over time and need sharpening to regain their optimal performance. Sharpening mower blades is not tricky and can comfortably be done with a tool such as a dremel with a sharpening stone. If you have not done this before, we have created a step-by-step guideline to help you.

How to sharpen lawnmower blades with a Dremel, step by step:

  • Step 1. Get the needed tools
  • Step 2. Disconnect the spark plug and inspect the existing set of blades
  • Step 3. Remove the center nut of the blade carefully and clamp it
  • Step 4. Sharpen the Blade with a Dremel
  • Step 5. Smoothen the edges and finish the blade
  • Step 6. Balance the blade and fix it back
(CC BY-SA 2.0) by osde8info

Lawnmower blades are located at the bottom of your machine. Most machines come with a single set of blades. Some bigger riding lawnmowers may have a second set working in parallel. The blades wear out after consistent working as they get used up or damaged by stones, junk, or other debris. If you see that the cutting patterns aren’t uniform, a blade sharpening is imminent. Sharpening a rotary mower blade requires removing the mower’s blade. Using a Dremel, you can even out the rough edges, develop the profile, and sharpen the metal surface. Dremel makes a rotary tool attachment that simplifies the sharpening task.

● Step 1. Get the needed tools

Using the right tools will help you finish the sharpening much quicker. To do the job, you need the following tools:

  • A pair of safety goggles and gloves.
  • Wrench set
  • Dremel
  • Clamps
  • Piece of wood
  • A bench vise to clamp the blades
  • Sandpaper
  • A sharpening or polishing stone

● Step 2. Inspection of existing lawnmower blades

Before removing and inspecting the blade, you should disconnect the spark plug cables. This will ensure that the engine can not start unintentionally. You do not want to work on the blades without this safety measure. Also, turn the ignition off. If you have an electric lawnmower, remove the batteries or disconnect the mains cable. Apply the parking brakes so that lawnmower stays stationary. If you have a platform, use it to raise the machine or incline it at an angle when removing the blades.

Lawnmower blades usually will become dull after around 30-40 hours of usage, depending upon the location where they are used. When you hit solid objects like rocks or metal, the blades can get damaged way sooner. So, sharpening becomes necessary. Before sharpening, the condition of the blades should be checked. Incline the lawnmower and touch the surface of the blades with your gloves on. Check for any cracks, irregular surfaces, and bends there. Also, look for the blade edge. Normally, it has a smooth profile with a sharp edge, but it gets damp as the blade gets worn out. As a final check, check if there is any hindrance as the blade moves and identify the part, if any. Mark one side of the blade before removing it to identify the correct orientation when you reinstall it.

● Step 3. Remove the center nut of the lawnmower blade carefully and clamp the blade

After you have turned the mower on its side (or upside down), loosen the nut at the middle of the blade with an adjustable or socket wrench. If it is difficult to loosen, spray the nut with some cleaner spray like WD-40 and wait few minutes. If the blade rotates while removing the nut, clamp a piece of wood to the lawnmower’s underside with C-clamps. This will keep the blade in place. After removing the nut, take off the blade from the lawnmower body.

Place the blade in a bench vise and tighten up as much as possible to hold it firmly in place. The blade comprises two cutting edges on opposite sides of one long piece of metal. You will have to work on each turn by turn.

● Step 4. Sharpen the blade with a Dremel tool

Sharpening the blade comes next. The very first step is to open the nose cap of your Dremel tool. Here you can see the threaded fitting where you have to insert your desired sharpening attachment, i.e., sharpening cylinder or rod, and then tighten it up with your hand easily. You can also use a key to tighten the tool.

Please turn on the tool, and set its rotation speed to about 2,500 rpm, a medium setting on most machines. Run the tool along the blade’s cutting edge with the extended, plastic support against the back. The attachment automatically grips the Dremel at a 30-degree angle. Suppose you are not using such an attachment. In that case, it is not a big deal because you can easily set your hand angle to about 20-25 degrees and easily sharpen your blade’s ends.

Follow the blade’s profile and develop the cutting edge by chipping off the metal from the rough surface. You have cut by going from the center to the periphery of the blade. Make sure that the cutting angle is not straight or sharp. It can damage the blade. Develop a sharp edge of the blade surface. A shiny surface will be an indication. Usually, 5-10 thrusts will do the job.

Safety remark: Always wear eye protection and gloves while working on the blades.

● Step 5. Smoothen the edges and finish the blade

To finish the blades and give them a longer life, you have to dampen the sharp corner minutely. It will help reduce the brittle nature, and the blade can last longer. You can perform this task by rubbing a sharpening stone along the blade edge. As a finishing step, you can also polish the blade edges with a buffer. Also, run the Dremel along the blade edge from tip to center. This helps to even the cut geometry of the blade.

● Step 6. Balance the blade and fix it back

For the machine and user’s safety, the rotating blade must be perfectly balanced. You can check the balance by hanging the blade on a nail on the wall horizontally. Let the blade hang on the support and notice that both sides should be hanging equally. If a side is heavier, it will hang lower. You can balance it by chipping off the rougher side by a Dremel. Give 2-3 rubs, and it will do the job. This step prevents any vibration and noise from the machine.

Fix the blade back by applying some grease to the central nut too. Check if the blades are rotating freely with no obstructions. Reconnect the spark plug and start the mower. Let it run for few seconds and check if you notice any strange sounds. If such is the case, take it to an expert. Otherwise, you are ready to go.

Frequently asked questions:

1. Can you sharpen mower blades with any other tool?

You can sharpen your mower blade with an angle or bench grinder or by a file as well. These tools can be used reliable, and each has its advantages and disadvantages:

– Using an Angle grinder:

Adjust the angle grinder with a grinding stone disk, if not previously in place. Angle grinders can be fitted with disks using sandpaper, wire brushes, and polishers. It will help if you put on heavy safety gloves to protect your hands against the blade. Against one of the thin edges of the blade, hold the grinding disk. Run the grinder side by side along the edge of the blade to level out any nicks, i.e., rough edges that commonly develop from hitting stones during mowing. The grinder will chip off the metal quickly.

– Using a File:

Using a file, you can easily do the job with your hands. Similarly, remove the blade and, using a file, give regular forward strokes to chip off the rough metal. Using a file, you have to be more careful as you are developing the profile. Carefully even it out. Use a sharpening stone to give a final touch.

2. Are lawn mower blades supposed to be sharp?

Mower blades should be aggressively sharp but not as sharp as a razor’s edge. You should be able to touch the blade with your hand without getting cut. Additionally, lawnmower blades that are too sharp get duller faster, resulting in sharpening more frequently and shorter blade life. A lawnmower blade with a bit damper edge will last longer.

3. Does wet grass dulls mower blades?

Mowing wet grass will not dull your mower’s blade any faster than dry grass, but it is not good for the lawn and makes the mower work harder. The wet grass clumps together due to the moisture, and removing it gets difficult. It does not directly affect the mower blade, but the moisture may create other issues like rusting.

Final remarks:

The suitable condition of blades is crucial for the optimum working of the lawnmower. With time, the lawnmower blades become dull and give uneven or rough cutting of grass. Worn-out blades require sharpening. You can use a simple rotating tool like a Dremel to polish the blade edge and surface. The Dremel is a handy tool and easily available. In this article, we have explained all the steps to use it. Generally, lawnmower blades require sharpening after 30-40 hours or 1 season. If they are taken care of properly and regularly, they will help keep the mowing experience attractive and fun.