How to Change the Blade on a Push Mower Safely
As an Amazon Associate we earn from qualifying purchases.
Changing blade on push mower starts with disconnecting the spark plug wire, or remove the battery on an electric model, so the engine cannot start while you work. Then drain the fuel if your manual calls for it, tilt the mower so the spark plug faces up, block the blade so it cannot turn, remove the blade bolt, fit the new blade with the cutting edges facing the correct way, and tighten the bolt to the torque in your owner’s manual. The steps below follow a rotary push mower with a blade bolt, the most common design. Reel mowers use a different cutting system, so check your model before you start.
Quick answer
- Disconnect the spark plug wire before you touch the blade. On an electric mower, remove the battery or unplug it.
- Block the blade with a piece of hardwood so it cannot rotate while you loosen the bolt.
- Mount the new blade with the curved edges toward the housing, then tighten the bolt to the torque your manual gives.
- If your mower has a reel instead of a rotary blade, the procedure is different. Check the owner’s manual first.
Know which kind of blade you have
Most push mowers sold for home lawns use a rotary blade. A single flat blade spins under the deck and cuts by impact. A reel mower uses several curved blades that spin on a cylinder and cut against a fixed bedknife, like scissors. The two systems share a few words in the catalog, but the blade change is not the same. Reel blades usually need the reel and bedknife adjusted together, and the step-by-step guide below does not cover that work.
Before you buy a replacement, match the blade to the model number on your mower or in the manual. Cutting width matters too. A blade that is too short or too long for the deck will not fit the mower correctly.
What you need
- Work gloves with a good grip
- A socket or wrench that fits the blade bolt
- A block of hardwood, about 2 by 4 inches, to hold the blade still
- A replacement blade that matches your model
- Your owner’s manual, for the torque setting and the blade orientation
- A rag or paper towel to wipe grease and grass from the spindle
Step by step
1. Make the mower safe to work on
Turn off the engine and let it cool. Disconnect the wire to the spark plug before you do anything else. A common reason to do this is that the engine cannot fire while the wire is off, even if the blade turns when you move it by hand. For an electric push mower, remove the battery or unplug the unit. The Murray support page for walk-behind blade removal gives the same warning: before you remove the blade, disconnect the wire to the spark plug.
2. Prepare the mower
Some manuals say to drain the fuel tank before you tilt a gas mower. Follow your manual on this point. If you tilt the mower, lift it on the side with the air filter and the spark plug facing up, so oil does not run into the carburetor or the air filter. Keep the mower stable while you work, and do not let it rest on a surface that can slip.
3. Block the blade
Slide a piece of wood between the blade and the deck, or wedge it against the blade tip, so the blade cannot turn when you apply force to the bolt. Do not hold the blade with your bare hands. Position the wood so it cannot slip when you loosen the bolt.
4. Remove the old blade
Use the socket to loosen the blade bolt. On many Briggs and Stratton engines the bolt has right-hand threads, so you turn it counter-clockwise to loosen it. Remove the bolt, the washers and the old blade. Keep the washers in order, because the Murray page notes that the washers are fitted in a specific way. Look at the old blade. If it is badly worn, bent or cracked, replace it rather than trying to repair it.
5. Clean the spindle and check the parts
Wipe the spindle and the blade mounting area with a rag. Remove grass build-up so the new blade sits flat against the mounting surface. Check that the washers and the bolt are in good condition. Replace damaged hardware.
6. Mount the new blade
Set the new blade on the spindle. Check the orientation before you tighten anything. The Murray page says to mount the blade with the curved edges toward the housing. Your manual may show a diagram of the correct direction, so follow whichever instruction matches your model.
7. Fasten the bolt to the torque setting
Fit the washers and the bolt as the manual shows. On the Murray walk-behind model covered by its support page, the bolt is tightened to 30 foot-pounds of torque. Other mowers use different values, so check your manual before you tighten. A bolt that is too loose can let the blade work loose. A bolt that is too tight can damage the threads or the spindle.
8. Reconnect and test
Remove the wood block. Reconnect the spark plug wire, or reinstall the battery on an electric model, only after the blade is secure. Stand clear of the blade and start the mower on a flat surface, then check that the blade turns freely. If the mower vibrates after the change, stop the engine, disconnect the spark plug again and recheck the blade orientation and the bolt torque.
Mistakes to avoid
- Leaving the spark plug connected. Disconnect it before you put your hands near the blade.
- Holding the blade with your hands. Use a block of wood instead.
- Installing the blade upside down. Check the curved edges and the manual diagram before tightening.
- Guessing at the torque. Use the value in your owner’s manual.
- Reusing a damaged blade. Replace a bent, cracked or heavily worn blade.
The reel mowers in this comparison
The products below are reel mowers, not rotary push mowers. The listings do not state a blade-change procedure, so the steps above do not apply to them directly. Use the listings to compare the machines, and use the owner’s manual for any blade or reel work.
The American Lawn Mower 1204-14 is a 14-inch, 4-blade push reel mower. The listing says it weighs 1 kg in its item weight field and gives a cutting width of 14 inches. The listing also says the mower is manual and has a red finish. It describes a reel cutting action that does not bruise the grass.
The Great States 304-14 is a 14-inch, 5-blade push reel mower. The listing says it has a cutting height range of 0.5 to 1.75 inches, 8.5-inch composite wheels, and heat-treated alloy steel blades. It weighs 9.3 pounds according to the listing.
The Scotts 304-14S is also a 14-inch, 5-blade reel mower with the same stated cutting height range. The listing gives its weight as 18.1 pounds and says it uses heat-treated alloy steel blades. The listing does not state a blade-change method.
The American Lawn Mower 1815-18 is an 18-inch, 5-blade reel mower. The listing says it is made of metal, weighs 27 pounds and carries a 1-year limited warranty. It is suited to dry grass under 4 inches, and the listing says taller grass may need multiple passes.
For each product, the listing is the source for the specs above. The listing does not give a procedure for changing the blades, so use the manual that came with your mower.
When to ask a professional
If the blade is cracked, bent, or the spindle is damaged, take the mower to a qualified small-engine repair shop. If you are unsure about the fuel system, the spark plug or the battery on an electric mower, ask a qualified technician before you continue. Electric mowers also have their own battery and power safety steps, so follow the manufacturer’s instructions for those models.
FAQ
Do I need to remove the spark plug to change the blade?
You do not need to remove the spark plug itself to change the blade. You do need to disconnect the spark plug wire so the engine cannot fire while you work. Many manuals and support pages give this as the first step.
Can I change the blade on an electric push mower the same way?
The basic steps are similar, but the power source is different. Remove the battery or unplug the unit before you touch the blade. Then follow the manual for your model, since the blade bolt, the torque and the orientation can differ from a gas mower.
How tight should the blade bolt be?
Use the torque value in your owner’s manual. The Murray walk-behind page gives 30 foot-pounds for the model it covers, but another mower may need a different value. Do not guess.
Which way should the blade face?
Mount the blade with the curved edges toward the housing, as the Murray support page says. Check your manual for a diagram, because the correct orientation can depend on the model.
Can I sharpen the blade instead of replacing it?
Sharpening is a separate task. If the blade is only dull, you may sharpen it, but a bent, cracked or badly worn blade should be replaced. Check the blade balance after you sharpen it.
Bottom line
If your mower has a rotary blade, disconnect the spark plug or battery first, block the blade, mount the new blade with the curved edges toward the housing, and tighten the bolt to the torque in your manual. If your mower is a reel model, such as the reel mowers listed above, the procedure is different, so use the owner’s manual before you work on it.
