How to Sharpen a Lawn Mower Blade

How to sharpen a lawn mower blade, step by step.

[@mdkarnish]

No need to empty the gas tank or remove the spark plug as one commented below. All you need to do is disconnect the plug wire. A mower should only be tilted with the spark plug in the upward position and never tilt a mower on it's side, as this can allow oil and gas to flow in areas of the engine that may cause issues. Wedging a block of wood should be at a right angle to the blade. Your method may bend the blade if too much force is required to remove the bolts securing the blade. I love the oil painting to prevent grass from adhering to the bottom of the mower deck. Thanks for taking the time to share.

[@powellgammill4265]

Nice job David. 7 years later still useful.

[@ericgtr]

Who doesn't love the internet! David, instead of waiting for 2 weeks for shop maintenance to be done to my mower, I followed your instructions and did it myself in just about an hour, my mower's as good as new now. Thanks for the great tips!

[@jasonmoore1900]

i love this guys narration style and his tone of voice.

[@gjensen500]

Thanks davidsloan2380 for the great tips. I like your use of old motor oil. Those farmers sure carry a lot of wisdom over the years. I enjoyed listen to your rooster crowing too. Thanks again.

[@Bluzrooster]

From a girl who doesn't know jack about lawn mower care, I appreciate this play by play show me how to do it!

[@servihomestead4324]

I like the idea of painting on the old oil to protect the metal. Thanks.

[@georgeklug481]

Installed these on a riding mower kzbin.infoUgkxetgfkJxfdT_B2vGYP-uNTLaBbim9OKTD . They were sharp out of the box, although I've never liked blade edges that were coated...not quite as sharp as I personally want. Using my belt sander, I removed the coating from the cutting edges and refined the edge enough to shave with them. So far, after three runs, these blades are holding up as expected. Even after hitting a few fallen 1/2 inch or so branches, the edges are still sharp as heck. No edge dings, no warping, etc. As far as installing them, the cutouts were of the proper size and shape to fit my aging Craftsman mower. Very satisfied.

[@CharlesAlvear]

Thanks for the great instructional video. I heard 45 degrees was the proper angle to sharpen the blade. Now I'm off to Home Depot to get me a blade sharpener for my drill.

[@Lonerider191]

Great information here. I would add, echoing at least one other comment, that mower blade installation should *always* be done with proper torque (typically around 40 ft. lbs). Correct torque is critical because problems can occur if the blade is installed with either too much *or* not enough torque on the installation bolts. Also, some mowers have special concave washers for the blade bolt(s) that need to be installed in the proper direction. Check the manual for both of these.

[@MainMatK]

It's nice to listen to a wise ole farmer. Love the spread sir. Thanks for the ole farmer secret with the oil. I'm gonna try that too. (and pollute my garden and grass and water, LMBO! ppl kill me sometimes). Thanks again sir.

[@Morgus79]

Thanks so much David, I needed your advice to get my mower back in shape for the season.

[@awparkermd55]

Great video. Learned something new - painting the bottom of your mower with the old oil to prevent rusting.

[@AnjelSnow]

clear and to the point video! loved it and it's very helpful.. thank you

[@imaniguana]

Great vid! Thanks for posting this. My personal preference is to scrap old grass off the bottom with a wood shim. That way the paint is not scraped or chipped off in the process.

[@TheConvivialCreator]

Great video. There were some things here my dad didn't mention. I saw you were wearing safety glasses, but didn't remind folks to do so as my dad did. :-) A couple of short cuts...if you don't choose to run your gas out, be sure to roll your mower on the side opposite of the filter otherwise you could get gas in your air filter - not good.

[@michelevyas5353]

David your video was so helpful and learned a lot wish I had watched your video when I changed the blade now I can do it so much easier after watching this love the oil under neath mower so grass doesnt stick did not know my oil drain plug is under neath the bottom will have to do that at the end of the year. Thank you so much god I wish we were neighbors

[@DustinSilva]

Fantastic video!! Thanks for sharing both high tech and low tech solutions!!!!!

[@folkhippiesmom1]

This is one of the best do-it-yourself vids I have seen. BTW - you have a wonderful voice, you should be on the radio :)

[@BrewCityRider]

Good video. The old farmer paint the deck with old oil trick was interesting. I would think that would actually attract debris though. Lots of comments about not wearing gloves when working with bench grinders. Well that is fairly common advice that you will read on the internet, but it's actually not accurate. Take a look at industrial safety rules from the various manufacturers and they all mandate the wearing of gloves with bench grinders. I always wear gloves when using the wire wheel, and sometimes when using the grinding wheel - just depends on the specific job. No way the wheel can "grab" and drag your glove if you have a properly spaced tool rest in place anyway.

[@u2mister17]

BS it keeps things from sticking. I mean, how much dirt can it hold? My problem is turning that engine upside down.

[@walkerpantera]

agreed with gee jay, perfect straight to point video demo, appreciate it and will follow it for my mower, thanks!

[@cristalsanmartin6239]

very useful! i like the trick of using the old oil to paint to protect the interior.

[@hanyoukimura]

Some very helpful tips, especially sharpening and balancing the blade. A couple things I want to mention. I don't feel its necessary to drain the gas out for this job. Removing the park plug means the engine has no way to ignite the fuel. Of course, if you have a fuel shut-off valve installed you can shut it and be extra safe if you really want and leave gas.

[@1pcfred]

My favorite way to sharpen my tractor blades is with an angle grinder. I finish dress them with a bench grinder or maybe a belt sander but I do the heavy removal with an angle grinder that is usually used for grinding weld beads. I use a pneumatic impact gun to remove, and replace the blades too. Beats fooling with hand wrenches. I don't grunt when I do it like the guy in this video did.

[@iliveoutside]

Nice tip on oiling the deck! thanks!

[@condor5635]

Chrizzly Atoms - The key instead of oiling the deck is to rinse the deck with water after each mow. It’s very simple. His mower was not properly maintained with that much crap underneath.

[@samanthanoble2579]

Wears of experience here. after the last mow (fall) clean the bottom with a pressure washer or water nozzle allow to dry and coat with ospho. done. That oil trick well the oil is not biodegradable its going to come off on your lawn your driveway etc and if you compost lol. Safety tip: I use a hand held grinder with the blade in the vise. Which ever type of grinder used the angle between the blade and the grinding wheel should never exceed 90 degrees. the video demonstrates a technique using approximately 135 degrees. the blade can dig into the wheel and lightning fast become a uncontrollable flying object.

[@25-8]

thanks. 😘

[@SubhiSHashwa]

Thank you, that was a very informative and helpful video.

[@cbgsinsal]

Thanks, David. Good job.

[@siberwolf33]

Thanks for starting the video with that rooster crowing. Had my headphones in and unbeknownst to me had the volume all the way up. Texting is my only form of communication now as I am completely deaf. My lawyer will be in contact.

[@netdoctor1]

Well, David... it appears as though everybody has an opinion. Lots of comments about gloves and grinding wheels. I think we've covered that by now. I like my 1/4" die grinder, but not everybody has the means. I think it's critical to try to reproduce the manufacturer's original angle if possible. Consider a maintenance routine that begins by removing the spark plug you intend to re-gap or replace. Leave it out until the last step. Then, turn that mower on the side with the dipstick tube to get to that drain plug (leave the oil cap on!). Less likely you'll drain oil into the cylinder than if you try tipping it front-wheels-up. Of course, that may vary from one manufacturer to the other. (My dad-blamed B&S mower doesn't even have a drain bolt. I'm somehow supposed to siphon that s**t out!). Remove the drain bolt, then drain your oil into your pan. After the oil is drained, tip it up again to pull the blade. I also saw a suggestion on the Deere site that says don't grind that leading edge to less than .4mm. I understand its a balance between sharp and tough, but I would never have left a .4mm blunt edge on my blades. But... I'm a transmission guy; I 'spose I should leave the technical stuff to the engineers, right?

[@kulajon]

Great video! I'd like to add; I'm not sure I'd go with the used oil brushing on the deck because of environmental concerns (beside that the oil would be gone before the first mow was over if you had a dusty lawn or you'd have oily mud gunk to deal with as well as clippings!) I also know that most blade bolts have a torque setting. Read your manual!

[@onetooyoung]

Very informative. Just what I needed. Thanks.

[@gregory891]

Good reminder to check blade balance after sharpening! You'll get a better drain of old oil with the engine warm, although most people NEVER drain the oil. FYI, Amsoil makes the only synthetic oil for lawn & garden equipment, similar pricing to conventional mower oils and a MUCH better product. Under mower decks should be cleaned after each cut, avoids most of the deck rusting issues. NOT very ecological to paint the under deck with oil oil, it's a terrible pollutant.

[@clientnumber09]

Thanks for the video, I should of watched this before I attempted. Nick from Chicago

[@periesicsd]

@coppertrail the most important of all is that your blade is in balance! It's the flywheel of the motor! Very very very important that it's in balance! If not, your mower start shacking and vibrating.

[@mwil3]

Nice video...Thanks for taking the time to put it together.

[@osi2484]

Binnenpad 1 is correct. Bench grinding method shown is good way to cause a jam between grinding wheel and mower blade AND the Hand that is holding the mower blade. Happens faster thank you can blink. D.S. should consider this.

[@baileywilson1236]

Great video. Helpful. Loe it from Queensland Australia

[@JoelDaMan112]

thank you for the balancing technique!

[@SouthTexasGal830]

wow nice video brief and too the point. I like the "oil painting tip now I feel I can do this myself instead of getting it done or buying a new one. :)

[@kentjohnson5704]

You should definitely go into radio. Golden Pipes!

[@airdaleva42]

Very informative, never considered balancing before. And using the old oil is something inventive. I use WD-40. Gpoing to try all your suggestions.

[@yellowbusguy]

Don't run the mower until the tank is empty because the carb will ingest debris and plug it up. Removing the plug is unneccesary if you have disconnected the lead. When you tip over the mower do it when the tank is low and make sure the tank is tipped upwards on the high side to prevent a spill.

[@angeloinferno6553]

would it be a good idea to polish the blade after using the grinder? I was just thinking that the finer edge would be better at cutting grass more effectively, and then grass, dirt, and water wouldn't be able to get into the little scratches left by grinding, would that help prevent rust too?

[@McMinnManiac]

i know a guy who changes oil weekly on his commercial scag . he gets 2x the amount of hours out of the machine in the end . So you can never change the oil too much . Also running 2 cycle in a 4 cycle engine is not a bad thing , it is actually better quality gas

[@acropetal]

Man, You make me wanna go work on my lawnmower : - )

[@maryannshepard6832]

fidely me to

[@solohoh]

Great instructive video, thanks

[@trekzilladmc]

Using the old motor oil to coat the underside of the deck won't cause your lawn to eventually die as it flakes off, will it?

[@tunnelthruair164]

Overall an informative video. Lawnmower on grass on its side a no no. Gas or oil can and most likely will leak on grass killing it. I never fill mower with gas while on grass either.

[@kenzob3256]

My mower blade has a star shaped hole and cannot balance on the cone to test for balance. What can I use to tell if my blade is balanced?

[@aaronjarnold78]

It is possible to start it by rotating the blade. Even just a small amount of rotation could make it fire up.

[@nburdik]

I wouldn't recommend grinding it with the edge down. The blade can get caught between the wheel and the rest causing the grinder to bind and very possibly injuring the user. I learned this the hard way.

[@capfl2k5]

everytime i sharpen my blades i think about that maximum overdrive movie.

[@TeamGopher]

Hi David, Nice work on your video. I am going to post it in my lawn care business forum to hopefully get you more views :) 5 Stars

[@hanyoukimura]

@hanyoukimura The other thing O wanted to mention is that deck sure was filthy. It really should be washed after each mow, this prevents grass buildup and stops rust from ever starting. My deck has a washout port which makes it really easy, but topping the mower and spraying it is also easy. Also, if you want to prevent rust, clean the underside of the deck really good, prep the surface, then spray on truck bed liner. It's extremely tough and will protect the metal.

[@russlehman]

Definitely. For one thing, it's just about impossible to get the blade straight and balanced again, and even if you could, if you banged it hard enough to bend it, you may have also cracked it, and a piece may come flying off at high speed. Spend the $20.00 or so for a new blade.

[@edcar10001]

hey about the oil on the bottom is it able to ignite and catch fire? or something?

[@Twisted86]

How long does that motor oil trick last on the mower? Brilliant idea of it works lol.

[@AbuGrabIt]

Good video. Thanks.

[@stradric]

1. It is highly unlikely for the motor to start. I think unhooking the spark plug is unnecessary. But if the mower doesn't have a safety line, I suppose it is possible that if you fling the blade while unscrewing, it could start the motor. 2. Use of the bench grinder is fine. You shouldn't be putting too much pressure on it anyway that would lead to what you are describing.

[@willpickett7899]

awesome video i never thought to use the motor oil on the bottom of the deck but im glad i seen your video i hope to see more in the future /subscribe

[@mariesheppard3750]

Good video and to the point thank you

[@IkeandMike1]

People always advise to remove the spark plug but really what's the likelihood the mower will start up and spin fast enough to take off your hand before you move your hand away? Good video though.

[@bbowling4979]

With the spark plug in, the cylinder will build pressure during the compression stroke if you happen to turn the crankshaft while trying to remove the bolt. When the crankshaft passes top dead center you reach the power stroke. With no spark the engine won't fire, but the pressure in the cylinder from the compression stroke can cause the crankshaft and the blade to suddenly jump forward!

[@eddie195777]

***** Better to be safe than sorry. Everyone can make up their own mind. I think it's worth the 60 seconds it takes to remove the sparkplug.

[@martyutley9683]

Very well explained, thank you.

[@PunaniLicker69]

i never changed the oil and i had my lawn mower for like 8 years. what happens if u dont change it?

[@DaPainterDude]

So I have a question. I have a 2016 craftsman t3200 riding mower with 48 in mowing deck with 3) 16 &1/4 in long blades. Not that it should matter, but in case someone needs to know. So when you remove the cutting blades is it necessary to grease any part of the shaft or bearings that spin the cutting blade? I heard some rattling coming from my mower deck. The riding mower is only 2 yrs old. There was a lot of grass build up. I hook my garden hose to the mowing deck after almost every mowing when done. I'm guilty of skipping it a time or two when in a hurry. So once I sharpen and balance the blade I should be good. Also I completely clean the underside of the mowing deck. I'm just curious about the shaft area that spins the blade. I'd like to address any issue while I have it apart right now. I appreciate any feedback or even if you're a troll and want to tell me how dumb I am, if it makes you feel tougher at the end of the day and keeps your ego throbbing then let it rip. Thank you ahead of time for any advice anyone may have for me.

[@zing1018]

it may seem excessive but if you happen to hit the blade and or key (depending upon what kind of lawn mower you have) and it starts up with your arm/fingers/foot under it you may think differently next time...

[@brianmccutcheon3205]

If someone doesn't know that the white thing on the back isn't a spark plug, they shouldn't attempt to sharpen blades. LOL....thanks for your video

[@DavidDavid-ft4ry]

never gloves with a grinder

[@leco781]

This was extremely helpful, thank you.

[@buddydry3183]

The rooster scared the shit out of my dog

[@russlehman]

If the wrench slips off the blade when you're tightening, you'll skin your knuckles. After you do this a few times, maybe you'll learn how to operate a wrench properly. It worked for me, anyway.

[@armandonunez7621]

at what angle do I sharpen the blade on an electric grinder?

[@pjmsullivan]

Great tutorial. Thanks a lot!

[@IPullingTractor]

The title of this video should read: "How to Sharpen & Balance a Lawn Mower Blade." Because balancing is very important for safely, to prevent damage to engine & deck, & to prevent tingling in the operator's hands.

[@tonyming6969]

@yellowbusguy He doesn't say so, but it IS a good idea to take the spark plug out because that sucker could still take a finger off if you turn it on a compression stroke.

[@launchpaad]

How would that happen with the spark plug wire removed?

[@carlosrodriguezv.7062]

Good job and advice

[@donaldmassaro7276]

As a vice you can take a welding rod and stick it on there and see if it balances straight across that's how I learned to do it when I was just a kid works every time

[@kevinnoble5988]

That works when your blade has a round hole. but many newer blades have a star hole and it doesn't work for them.

[@launchpaad]

Removing the spark plug is a bit excessive not to mention it will allow dirt/grass to get into the cylinder.

[@evensteve284]

@Drone696 I don't know about that man. The mower shown has the blade directly connected 2 the crank shaft. I don't think either of your mowers R set up like that. If the piston happens 2 B at the top of the cylinder, before the power stroke, & by pushing on the blade you cause the spark plug 2 fire, that motor could start! Good bye fingers, hand, who knows? I'd play it smart & not take the chance. It's a quick & painless step that avoids a potential disaster. REMOVE THE SPARK PLUG! Cheers

[@evensteve284]

@osi2484 Binnenpad 1 is correct only if U don't know how 2use a bench grinder! I was a machinists 35+ years & used a bench grinder almost every day. When sharpening a tool or blade, ALWAYS grind INTO the cutting edge; NEVER away from it. U have 2learn how 2do this safely. Avoid dangerous kick-back by using the steady rest & keeping the part of the blade you are sharpening above the center line of the grinding wheel. If bench grinders make U nervous (they should), go with 1of the other methods.

[@OldPowerRevived]

Putting a board against the blade that way can bend the blade, causing a mean vibration. Keep your wood 90deg to the blade.

[@Drone696]

Dude, I do landscaping with a John Deere 1545, and a Honda HRH 536 HXE. I would NEVER take out the sparkplug, when I sharpen my blade (one time every week) ..Also the way you did it, the blade did'nt rotate 1 inch, then why do it..?? I use a belt grinder for the Honda blade, and also for the 3 blades on my John Deere 1545.. You are right, they dont need to be perfect, as long as the angle is acceptable..

[@imaginesc4]

Great tips!

[@dvrman]

I just use something larger, like a long socket, that fits the inner diameter of the star shape.

[@keeza333]

lawn mowers start up all the time on there own . also ghost's try to start them up if your working on them . always take out that spark plug first .

[@normynull]

great video. Thanks

[@jonr5000]

Thanks for the excellent video (except for gloves with a grinder).

[@rickman33]

it protects it from rusting and keeps the grass from sticking.

[@littleand9250]

never gloves when grinding via bench style

[@2NDLTSTEEN]

hmm I would not use old motor oil as rust shield , due to the sulfur levels in old motor oil it could accelerate the rust process...

[@jrstow86]

lol pull your spark plug and drain the fuel, because maximum overdrive.

[@robertocarlos1305]

Thank you for your video. Very well done =)

[@wcjcnc]

Great video! Thanks!

[@lizwharton1023]

The rooster shared the shit out of my cat! And the machine sound sent him running.

[@mdkarnish]

Liz Wharton

[@funkyjones]

When the sun beats down and I lie on the bench, I can always hear them talk...

[@sylvanir]

I love the video, but there was a huge missed opportunity to talk about when a blade needs to be replaced. As the blade cuts grass, the grass passes over the fin on the back of the blade, which provides the lift. When this fin starts to get thin and flake metal, the blade should be replaced. Also, NEVER use a 'universal' blade on a lawnmower. Universal blades are notorious for not mounting correctly, and there have been incidents with them coming loose and flying off @ 3600 RPM (over 10 MPH)

[@GTOGreg]

AIN'T GOT NO GAS IN IT! Um Hmmm. I reckon I'll try that der oil trick. Um hmmm. It ought to do good at keepin' 'em clean. uhhh. Some people call 'em kaiser blades, I call 'em slang blades. Um hmm. A'right den. Thanks for the video...great tips!

[@therealkenk]

great video. thanks. 5 stars!