Learning how to sharpen a push reel lawn mower is an essential skill for maintaining a pristine turf. Sharpening the blades on a push reel lawn mower creates the scissor-like cut that defines a healthy lawn. A dull mower tears grass, leaving it vulnerable to disease and giving it a ragged, brown appearance. A sharp reel, however, provides a clean cut that promotes vigorous growth and a lush, green carpet.
This guide will walk you through the entire process, from gathering tools to the final adjustment. You’ll find it’s a manageable task that saves you money and ensures your mower performs at its best.
How To Sharpen A Push Reel Lawn Mower
The core process involves two main actions: lapping the reel and sharpening the bed knife. Lapping is the process of grinding a perfect, uniform edge onto the reel’s spinning blades by applying an abrasive compound. The bed knife is the stationary blade at the bottom that the reel spins against; it must also be sharp for a clean cut. We’ll cover both methods.
Tools And Materials You Will Need
Before you begin, collect these items. Having everything on hand will make the job smoother and safer.
- Work gloves and safety glasses
- Adjustable wrench or socket set
- Screwdrivers (flathead and Phillips)
- A sturdy workbench or stand
- Fine-grit valve grinding compound or specialized reel lapping compound
- A flat mill file or a dedicated bed knife file
- A feeler gauge set (for adjustment)
- A putty knife or stiff brush
- Light machine oil or WD-40
- Rags or paper towels
- A wooden block (optional, for supporting the reel)
Step 1: Preparation And Safety
Always start with safety. Disconnect the spark plug wire on gas mowers to prevent any accidental starting. For all mowers, ensure the reel cannot spin freely during initial handling.
Thoroughly clean the mower. Use the putty knife and brush to remove all caked-on grass, dirt, and debris from the reel, bed knife, and inside the housing. This gives you a clear view of the cutting components and prevents grit from interfering with the sharpening process. A clean mower is easier and safer to work on.
Step 2: Checking The Reel-To-Bed-Knife Contact
Before you apply any compound, you need to assess the current state of the blades. This tells you if a simple lapping will suffice or if more significant work is needed.
Apply a thin, even marker line or a dab of machinist’s blue dye along the cutting edge of the bed knife. Then, manually rotate the reel backwards so the blades contact the bed knife. Rotate it a few full turns.
Stop and look at the marker line on the bed knife. If it is worn away evenly along its entire length, the alignment is good. If sections remain, it indicates low spots where the reel is not making contact. A very uneven pattern might mean the reel is bent or the bed knife is warped, which requires professional help. For most well-maintained mowers, the wear should be fairly even.
Step 3: Adjusting The Bed Knife
For the lapping compound to work effectively, the reel blades must be touching the bed knife lightly along their entire length. This is done by adjusting the bed knife.
Locate the adjustment bolts or nuts at each end of the bed knife. They are usually on the side plates of the mower. Loosen the locking nuts first. Then, slowly turn the adjustment screws to move the bed knife closer to the reel. You want a light, even contact. A good test is to try to pull a strip of newspaper through the cutting point; it should be snug but not impossible to pull.
Once you have a slight drag across the entire length, tighten the locking nuts securely. Be careful not to overtighten the adjustment, as this will create too much friction during lapping.
Using A Feeler Gauge For Precision
For the most accurate setup, use a feeler gauge. A common starting gap before lapping is about the thickness of a piece of newspaper, or 0.003 inches. Insert the gauge between the reel blade and bed knife at several points. Adjust until you feel a slight drag on the gauge strip. This ensures a perfectly parallel setup for an even sharpen.
Step 4: Lapping The Reel
This is the main sharpening step. Lapping uses an abrasive paste to wear down both the reel and bed knife simultaneously, creating a perfectly matched cutting pair.
- Apply a generous amount of valve grinding compound evenly along the cutting edge of the bed knife. Don’t be shy with it; you can always add more.
- Put your gloves back on. Begin rotating the reel backwards manually. You want to spin it in the opposite direction of its normal operation. This ensures the compound works effectively between the two surfaces.
- Continue rotating for several minutes. Apply more compound if it dries out or seems to lose its abrasiveness. You should feel a consistent, gritty resistance.
- Periodically stop and wipe away the old, blackened compound with a rag. Reapply fresh compound and continue. You’ll do this several times.
- The process is complete when you see a bright, shiny, and continuous strip on each reel blade and along the entire bed knife. This indicates full, even contact.
- Thoroughly clean off all compound residue using a rag and a degreaser. Any leftover abrasive will rapidly wear down your newly sharpened blades.
Step 5: Sharpening The Bed Knife
Sometimes, the bed knife needs a more direct touch-up, especially if it has nicks or a worn edge. Lapping may not remove deeper imperfections.
You will need to remove the bed knife for this. Note its exact orientation before taking it off. Unbolt it carefully from the mower’s sole plate.
Secure the bed knife in a vise, protecting its surfaces with soft jaws or wood blocks. Using a fine mill file, sharpen the beveled edge. File in one direction only, following the existing angle. Use smooth, consistent strokes. Check your progress often to avoid removing to much metal. The goal is a straight, sharp edge, not to reshape the entire piece.
Once sharp, deburr the back side of the blade with a few light passes of the file to remove any wire edge. Reinstall the bed knife, making sure it’s seated correctly and tightened securely.
Step 6: Final Adjustment And Testing
After lapping and cleaning, you need to set the final cutting clearance. This gap is slightly larger than the lapping setting.
Back off the bed knife adjustment screws slightly to create a small gap. Using your feeler gauge, set a clearance of 0.001 to 0.003 inches along the entire length. This tiny gap prevents the blades from binding during normal mowing but is close enough for a clean shear.
Reconnect the spark plug wire on gas models. Test the mower on a small patch of grass. The reel should spin freely and the cut should be clean and even. Listen for any scraping or binding noises, which indicate the gap is to tight.
Step 7: Lubrication And Maintenance
Proper lubrication is crucial after reassembly. Apply light oil to all the reel bearings, axle points, and the adjustment threads. This prevents rust and ensures smooth operation.
To keep your mower sharp longer, always clean it after each use. Avoid hitting rocks, roots, or hard objects. Store your mower in a dry place to prevent corrosion on the blades. A quick touch-up lap once a season is easier than a major sharpening job every few years.
Common Problems And Solutions
The Reel Binds Or Scrapes After Adjustment
This usually means the clearance is set to tight. Back off the adjustment screws a quarter-turn at each end and retest. Also, check for leftover lapping compound or debris caught between the blades.
An Uneven Cut Or Striping
This indicates the reel-to-bed-knife contact is not parallel. Re-check the adjustment along the entire length with a feeler gauge. The bed knife itself may also be warped or the reel could be out of true, which are more serious issues.
The Mower Still Tears Grass
If you’ve completed the sharpening but the grass is still torn, the blades are likely still dull. You may need to repeat the lapping process for a longer duration with fresh compound. Ensure you achieved that uniform shiny strip on all edges.
Frequently Asked Questions
How Often Should I Sharpen My Push Reel Mower?
For average use on a typical lawn, you should sharpen your reel mower at least once per mowing season. If you mow frequently or have a large lawn, you might need to do it twice. The telltale sign is when the mower starts tearing grass instead of cutting it cleanly.
Can I Use A File To Sharpen The Reel Blades Directly?
It is not recommended to file the individual reel blades by hand. Filing them unevenly can ruin the precise cylindrical geometry of the reel. Lapping is the preferred method because it maintains the correct relationship between the reel and the bed knife, which is critical for a good cut.
What Is The Difference Between Lapping And Grinding?
Lapping is a fine finishing process using an abrasive paste to create a precise fit between two surfaces—the reel and bed knife. Grinding involves using a powered stone to aggressively remove metal, often to reshape a damaged blade. For routine maintenance, lapping is sufficient; grinding is a job for a professional with specialized reel grinder equipment.
Is It Worth Sharpening An Old Reel Mower?
Yes, if the mower’s frame is sound and the reel isn’t bent or pitted with rust, sharpening can restore an old mower to like-new performance. It is often more economical than buying a new one. However, if components are severely worn or damaged, the cost of professional repair might not be worth it.
Can I Sharpen A Reel Mower Without Removing The Blades?
Yes, the standard lapping procedure described in this article is performed without disassembling the mower or removing the reel. This is one of it’s main advantages. Only the bed knife needs to be removed if it requires direct filing due to damage.