Learning how to sharpen reel lawn mower blades is a key skill for any homeowner who values a perfect cut. Sharpening the blades on a reel mower requires a specific technique to maintain their precise scissor-like action. Unlike a rotary mower with a single spinning blade, a reel mower cuts grass like scissors, where the spinning reel blades pass against a fixed bed knife. This guide will walk you through the entire process safely and effectively.
How To Sharpen Reel Lawn Mower Blades
This section covers the complete, step-by-step method. You will learn to assess your mower’s condition, prepare it for work, and execute the sharpening itself. Having the right tools and a clean workspace makes this job much simpler.
Tools And Materials You Will Need
Before you begin, gather these items. Being prepared saves time and ensures you can complete the job without interruption.
- A set of wrenches or a socket set (size varies by mower model)
- Work gloves and safety glasses
- A sturdy workbench or table
- A clean cloth and a wire brush
- A reel mower sharpening kit (typically includes lapping compound)
- A medium-grit sharpening stone or honing stone
- A flat file for the bed knife
- Light machine oil or WD-40
- A piece of wood or a block
Step 1: Safety First And Mower Preparation
Always start with safety. Put on your gloves and safety glasses to protect your hands and eyes from metal filings and debris. Ensure the mower is on a stable, level surface. If the mower is electric, disconnect the spark plug wire or battery. For a manual push mower, this step is obviously simpler, but caution is still key.
Cleaning The Cutting Assembly
Thoroughly clean the reel and bed knife area. Use the wire brush to remove all caked-on grass, dirt, and rust. Spray a little light oil to help loosen stubborn debris. A clean surface allows you to clearly see the cutting edges and make a proper assesment of their condition.
Step 2: Assessing Blade Condition And Adjusting Contact
You need to check if your blades actually need sharpening or just an adjustment. First, rotate the reel and look for nicks, dents, or sections that look visibly dull. Then, perform the paper test. Slide a strip of paper between the reel and bed knife at various points as you slowly turn the reel. It should be cleanly snipped. If it tears or crumples, sharpening is needed.
Checking Bed Knife Alignment
The bed knife must be parallel to the reel. Many mowers have adjustment bolts at each end of the bed knife. Loosen these slightly. Place a business card or a thin strip of paper between the reel and bed knife at one end, adjust until it just grips, then check the other end. The tension should be even. This alignment is crucial for the lapping process to work evenly.
Step 3: The Lapping Process (Primary Sharpening)
Lapping is the core method for sharpening reel mower blades. It involves applying an abrasive compound to the bed knife and rotating the reel backwards, allowing the abrasive to wear both surfaces into a perfect, sharp match.
- Apply a generous amount of lapping compound (usually a thick, gritty paste) evenly along the entire length of the bed knife’s cutting edge.
- Carefully rotate the reel backwards. You want the blades to move against the bed knife in the opposite direction of normal operation. Do this slowly and consistently.
- Continue rotating for about 50 to 100 revolutions. The compound will turn dark as it removes metal. Periodically apply a little more compound to keep the abrasive action effective.
- After lapping, thoroughly clean off all the compound from both the reel and bed knife using a cloth and a degreaser. Any leftover abrasive will rapidly wear down your newly sharpened edges.
Step 4: Honing The Reel Blades (Fine Tuning)
After lapping, you may need to hone individual reel blades, especially if there were small nicks. Use a fine or medium sharpening stone. Hold the stone against the back (non-beveled) side of each reel blade as you rotate the reel forward. Use light pressure. This step removes the burr created during lapping and refines the edge. It’s a finicky process but can make a significant difference in cut quality.
Step 5: Sharpening The Bed Knife With A File
The bed knife also needs attention. Secure the mower so the bed knife is accessible. Using a flat file, sharpen its beveled edge. Maintain the original angle, using smooth, forward strokes. File only in one direction, not back-and-forth. Check your progress often to ensure you are keeping the edge straight and even along its entire length. A sharp bed knife is just as important as a sharp reel.
Step 6: Reassembly And Final Testing
Once all parts are sharp and clean, wipe them down with a light coat of oil to prevent rust. Re-tighten any adjustment bolts you loosened, following your mower’s manual for proper clearance—often about the thickness of a piece of paper. Reconnect any spark plug wires. Finally, perform the paper test again at several points along the bed knife. The paper should slice cleanly and easily, indicating a successful sharpening job.
Common Mistakes To Avoid When Sharpening
Even with good instructions, it’s easy to make errors. Being aware of these common pitfalls will help you achieve a better result and avoid damaging your mower.
Over-Tightening The Bed Knife
Setting the bed knife too close to the reel is a frequent error. It creates excessive drag, wears the blades quickly, and makes the mower very hard to push. The goal is light, even contact, not a tight grip. Always use the paper strip method to set the correct clearance.
Using The Wrong Abrasive Or Tool
Never use a rotary tool like a Dremel or an angle grinder on your reel blades. These tools remove metal too quickly and can ruin the precise curvature and angle of the blades. Stick to lapping compound and hand files or stones designed for this purpose. The controlled process is essential.
Skipping The Cleaning Step
Attempting to sharpen dirty blades is ineffective. Old grass and grit will contaminate your lapping compound and prevent it from working properly on the metal surfaces. It can also cause uneven wear. Always start with a meticulously clean cutting assembly.
How Often Should You Sharpen Your Reel Mower Blades?
There’s no fixed schedule. Frequency depends on how often you mow, the size of your lawn, and whether you encounter debris like sticks or stones. A good rule is to check the cut quality every 10-12 mows. If the grass looks torn or ragged instead of cleanly sliced, it’s time for a tune-up. For a typical suburban lawn used weekly, an annual sharpening is often sufficient, but always let the condition of the cut be your guide.
FAQ About Reel Mower Blade Sharpening
Can I Sharpen Reel Mower Blades Without Taking Them Off?
Yes, in most cases you can. The standard lapping and honing procedures are designed to be performed with the reel and bed knife still mounted on the mower. This is actually prefered because it maintains the critical alignment between the parts. Removal is usually only necessary for major repairs or if the reel bearings need service.
What Is The Best Lapping Compound For Reel Mowers?
A medium-grit, water-soluble lapping compound specifically made for reel mowers is the best choice. These compounds are the correct abrasiveness for the job. Avoid using very coarse automotive valve grinding compound, as it can be to aggressive and remove to much metal too quickly, potentially damaging the precise edges.
How Do I Know If My Bed Knife Needs Replacing?
Inspect the bed knife for deep grooves, pitting, or an edge that is no longer flat. If, after filing, you cannot establish a consistent sharp edge along its entire length, or if it is visibly worn down, replacement is needed. A damaged bed knife will never allow for a clean cut, regardless of how sharp the reel is.
Is It Cheaper To Sharpen Or Replace Reel Mower Blades?
Sharpening is almost always more cost-effective. A sharpening kit is inexpensive and can be used for many years. Professional sharpening services are also available. Complete reel and bed knife replacement is a significant expense and is typically only required after many years of use or severe damage from striking a solid object like a rock.
Why Does My Reel Mower Still Cut Poorly After Sharpening?
Poor cutting after sharpening usually points to incorrect adjustment. The most likely cause is that the bed knife is not parallel to the reel, or the clearance is too loose. Re-check your adjustments with the paper test along the entire length. Also, ensure you cleaned off all the lapping compound, as residue can impede the scissor action.