# Sharpening mower blade



## RDS (Feb 29, 2008)

I have your basic Craftsman gas-powered push mower. I manage to maintain the engine and the rest of the mower myself, but have never attempted to sharpen the blade, and it needs it.

Is there an idiot-proof way to do this? The only thing I've ever sharpened before is a pencil. I'm not averse to buying new tools if necessary. I gather it's important that the blade stay balanced, and am looking for a method that helps a first-timer to do that, as well as avoid any other possible pitfalls of the process.

The only possibly-relevant tool I have is a 4.5" hand-held grinder. If a bench grinder is what it takes, I could get one. I'm also curious about gizmos like the Work Sharp. I figure these are the kinds of things that I could invest in and they would eventually pay for themselves, if they work well.

Or if there's a by-hand method that's better for a newbie (i.e. less likely to screw it up), I'm open to that too. Just looking for a method that uses readily-available tools and materials.

Thanks for any tips.


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## Grampa Bud (Apr 6, 2009)

It's really pretty simple, I started rounding over the blades on my dad's mowers when Iwas eight. I'm 63 now and have finally been allowed to use the power tools on the bench and if the old boy sees this from UP THERE I know he will figure some way to smack me up side the head ! Since you are just starting I would suggest the two hand method until you feel you have the hang of it. Pull the blade completely off the engine shaft and temporarily throw the bolts (nuts too) in a little oil. Tighten the blade in a solid benchvise so the jaws are between the hub and the inside end of one of the cutting surfaces with the cutting edge looking straight up and the leading as near perfectly horizontal as you can eye ball it. You will need a good heavy 12" Bastard file for metal and the bottom of the mower blade should be looking away from you. Take a look at the cutting edge to see how straight it is. You can run the flat side of the file horizontaly across the leading edge four or five times to make a nice straight edge to start with. Then using the flat side of the file grab the ends of the file, one in each hand and from horizontal drop the trailing end of the file to about a 30 deg. angle and note how much -or little- the file matches the angle on the cutting face of your blade. Start with firm lite strokes from the inside (HUB END) going out to the end of the blade. You can do heavier strokes as you go, but try to maintain that 30 deg angle at all times. When the leading blunt edge comes down to nearly a hair line STOP. Now do the same with the opposite blade. You are almost done. Turn the blade around so that the bottom of the blade is facing you. Looking at it this way you may see little points of metal sticking out at you just behind the leading edge. With the blade back in the vise (bottom looking at you) put the file flat on the bottom of the blade and only filing in one direction (from the leading edge towards the rear of the blade) file lightly just enough to get rid of those tits. be carefull of the blade it is very sharp at this point. To roughly check the balance of the blade lay a 16-20 penny nail on the work bench and place the blade center on the nail with them being exactly perpendicular to each other. You may have to hold one end or the other up gently, but with a light touch you should be able to tell if one tip is always the first to fall. If you think you have one put it back in the vise and take 6 strokes to the face of the heavy tip. When you are happy get your lubbed bolts & nuts, put the mower back togedda and get that damn lawn done.


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## RDS (Feb 29, 2008)

Thank you for taking the time to describe the process in so much detail, Bud. I think I can manage that. I will have to borrow my neighbor's bench vise but the rest of it seems doable. Cheers.


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## Chemist1961 (Dec 13, 2008)

G B, 
You Rock. Very Thorough. 

How are you with new style serated bread knives and serated knife sharpeners? Have a sharpening kit, fine with regular blades but not sure I want to mess with a good Heinkel knife.


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## Grampa Bud (Apr 6, 2009)

Chemist1961 If you or my wife or anyone else wants to wrangle with serrated blades,I only have one suggestion. Go to a saw/drill bit/scizzor sharpening service not your local tool rental shop. They are the only ones that can reproduce the serration "waffle" accurately. Have fun.


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## DangerMouse (Jul 17, 2008)

chemist,
i just use one of these and my bench vise to sharpen my serrated edged knives... 
http://www.ejabs.com/images/knifes/1.jpg
but if you google serrated knife sharpener 
you will find many kits to do this at varying prices and in different styles.

DM


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## DangerMouse (Jul 17, 2008)

oh, and RDS, i've used both, angle grinder and bench vise to sharpen my mower blades. a good eye and a little caution is all it needs.
maintain balance....

DM


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## mattman (Mar 9, 2009)

Be careful using a power grinder to sharpen a mower blade. Too much heat can damage it and create a hazzard.


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## Kap (Jun 20, 2008)

I got one of these as a stocking stuffer for Christmas.

I'd like to offer you a review on it, but it's still in the package.

Looks "gimmicky" to me. Oh well....maybe I'll open it this weekend and try it out. I got a couple dozen blades to sharpen.


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## RippySkippy (Feb 9, 2007)

WGD...not entirely true....

I have this sander at home for the work shop...and I'll tell ya...it'll beat the socks off of a "traditional" wheel grinder for sharpening tools INCLUDING lawnmower blades. Install an 80 grit belt and knock your self out. I have a 7' lawnmower with 3 blades and have sharpened them many times on this sander. The true value of this machine is that since it has the belt, it doesn't over heat the blade removing the temper.

With a 120 grit belt, you can put a fine edge on tools like axes and CONSTRUCTION chisels, not mortising chisels. If you're contemplating the purchase of a grinder, I'd really suggest you take a peek at this it's a bit higher in price...BUT it'll do a much better job AND you get a cool strip sander for shop use. Just be careful and don't start sanding metal with out first cleaning the wood dust out of the machine....DAMHIKT...


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## Maintenance 6 (Feb 26, 2008)

I always use a 4-1/2 angle grinder first to get all the nicks out and then follow up with G.B.s file method. Before you try to balance, get all the gunk and residue off of the blade. I've used oven cleaner with pretty good success for this. Where the sharpened area meets the rest of the blade, there should be a slight radius. You shouldn't file it into a tight corner. The radius will relieve any stresses and prevent a crack. If, you do come across any cracks, anywhere in the blade, toss it and buy a new one.


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## ptcity (Apr 4, 2009)

I think the best thing to do is to simply buy a new blade. They are not very expensive. Removing the old one can be a bit tricky. Block the blade with a brick or piece of wood and loosen the bolt holding the old blade on. If the bolt is stuck, then use a rubber mallet with a sturdy wrench to knock it loose.

Don't forget to wrap the old blade in newspaper before trashing it so the garbage man won't lose his fingers.


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## Maintenance 6 (Feb 26, 2008)

If it'll cut off fingers, it'll cut off grass. Keep using it. :thumbup:


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## Grampa Bud (Apr 6, 2009)

Amen brudda !!


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## RippySkippy (Feb 9, 2007)

I agree... It's a waste to just toss a blade away UNLESS it's either damaged or worn out.


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## teamcampreder (Jul 23, 2011)

I was planning on trying to sharpen my own blade, but dont have a bench vice (or a work bench) for that matter. Is it a total mistake to wear a heavy duty glove on one hand and try to do it that way, one side at a time?


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## Grampa Bud (Apr 6, 2009)

You could use a heavy glove on one hand to hold the blade while working the file with an ungloved hand. However if you have no tools or restraints for the blade it might be better to get professional help. You need wrench(s) to get the blade off and to put it back on securely. If you have an old tree stump sitting around you might brace the blade on it while sharpening, but not holding it securely will most likely do more harm to the blade -and probably you- than helping it.


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## teamcampreder (Jul 23, 2011)

Hmm, I have a torque wrench, got the blade off and know what to set it at to get it back on, I have also done all my other services (oil, air filter, spark plug), my lawn boy is reallly easy to work on. I do have a big stump in the backyard, maybe i will try that out, or maybe its time to cough up some dough on a workbench and bench vice, I am sure it will come in handy beyond this project.


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## Grampa Bud (Apr 6, 2009)

Yes it will. Good Luck and happy mowing.


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## biggles (Jan 1, 2008)

"one swipe" :thumbsup: of a gringers wheel (bench or hand held)on both sides and back parts very lightly.a wire wheel on the grinder bench there will clear the built up grass..nice and some what new:wink:....just note how you take it off and reinstall it should be stamped or nut washer rust mark.. will direct you.just put a slight sharpness video is cool he doing it with no fluids within the mower never tip a gas/oil filled one like this.you just need to tilt it slightly to break the bolt loose 6"piece of 4 X 4 works.i do both sides he only does one to get the angle... http://www.youtube.com/watch?v=eXLygHF6El4 bos wrench works the best if your doing it blindreaching under it...vasaline the bolt going back in...


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## 95025 (Nov 14, 2010)

RDS said:


> I have your basic Craftsman gas-powered push mower. I manage to maintain the engine and the rest of the mower myself, but have never attempted to sharpen the blade, and it needs it.
> 
> Is there an idiot-proof way to do this? The only thing I've ever sharpened before is a pencil. I'm not averse to buying new tools if necessary. I gather it's important that the blade stay balanced, and am looking for a method that helps a first-timer to do that, as well as avoid any other possible pitfalls of the process.
> 
> ...


Over the years of doing professional lawn-mowing, all I ever used was a 4" angle grinder. Lock the blade into a bench vise and go to town. Grind it down to a nice sharp angle, not a blunt angle.

I also found that I could only sharpen blades once. If I sharpened them as second time, I just could not get a good cut out of them. So I sharpened them once, then replaced them the second time around.


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