Lawn mower blades

Dergyll

Dergyll

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Feb 24, 2021
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Any tips?

Was thinking of going in with some files and sandpaper. After removing it of course... I keep having this nightmare of it turning on and turning my hands into mulch meat.

Sounds silly but what grind should I give it and how "sharp" should it get?

Appreciate all input, thank you.
 
I just use a file or angle grinder depending on how much it needs and whether it's the field blade or lawn blade. Since these blades are so soft I don't think it's worth much effort since it will lose its edge very quickly, at least the blades on my mower.
 
Remove the blade, yes. Follow the original angle, and use a grinder. Unless your blade(s) has/have very little damage, a file will take a very long time to remove it. Sandpaper even longer. Once you have ground the damage out, check and correct the blade(s) for balance - most hardware stores will have a simple blade balance tester for sale. Next, take that file and lightly blunt the leading edge of the blade until it has a flat about 1/64" wide along the full length. This will hold its shape much longer than a fully sharp edge and cut just as well.
 
Great tips guys, thank you. Dont have a grinder yet so will have to do it with the file. Someone said something about checking the balance of it after sharpening so it doesnt wobble when spinning, will do that too.
 
Angle grinder, belt grinder, bench grinder. Easy peesy. If its rounded off have a small bucket of water so you dont overheat the blade. Follow the old angle. How sharp? Ive done mine on 60 grit disc on my angle grinder. 20 grit belt on a belt grinder. Gets sharp enough for sure. I never debur mine.
 
Used to use a file, but got a Work Sharp a few years ago and use that now, with the 80 grit belt. So much better and faster.
 
Mill bastard file (10-12 inch} will handle it, if no major repair is needed. Put the blade in a vise. A file with a handle is a plus. And some heavy gloves will help protect your hands. Nothing fancy is needed, otherwise. Anything too refined will get beat up in a hurry, in use. All you really need is a cleanly-apexed edge, enough to verify a burr.
 
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All my mower blades and customers mower blades go out with 280 grit finish at 45°. I lightly touch the top and bottom of the edge with a very fine hone to refine the apex.
 
powered grinding and files are the fastest methods.
i have 2 different black mower blades, sharpen them with diamond rods and what have you, even up to mirror finish (cuts xerox paper) but after 1 mowing session the nice sharpness is gone. still sharp enough for more mowing sessions so i sharpen not frequenter than every 10 sessions.
Sometimes the mowing blade would cut through fresh soil patches (or branches, fruits, nuts, dry soil clumps), ruining all my sharpening efforts in a whim, so i keep that in mind when sharpening and not overspend efforts on it. I do sharpen these blades more out of enjoyment than necessity or urgency, and next time I'll add photos to the [wdyst]-thread.

it is soft steel (and not stainless), it's easy to remove metal so personally i can't use a file or powered grinder because I'd take off more material than necessary; it's funny to see the altered geometry after each sharpening lol. i must have tried Ruixin Pro III too but can't remember how that went.

I might buy a new small mower in future. Sharpenability and availability of cheap replacement blades be features I'll be looking for. Federer plays first clay match today in a long time.
 
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12" mill file brought to a burr, check for balance by hanging off a nail or similar. There is zero point in going finer, these blades are not hardened to any appreciable degree nor would you want them so. Far better to bend if it hits a stump or root than to break and go flying or be tougher than your motor shaft.

If you inspect the blade after about an hour of mowing you'll find it is mellowed back to a nice aerodynamic cutting edge. Brand new ones form the store aren't truly "edged".

Reel mower blades tend to be harder and can hold a sharp corner for a season or more of regular mowing, but then there's no danger of them flying off at high speed.
 
I have been doing this way for many years.........take off the spark plug wire first of course!! I use a Dremel tool with a sanding drum. Make light passes to the outer 3/4" to 1.5" of the blade. Any further is kind of a waste as that is where 85% of the cutting is done. I don't grind it down to a sharp point as were cutting grass here... You are not removing enough metal to throw off the balance so that isnt an issue. I did this to my Honda that used two blades and the Toro that has one. Honda was 12 years old and Toro is 8 and still have no balance issues.. Same blades..And I never have to remove them.
 
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Good advice above, much better than what I offer as this is not a precision procedure in my mind, however, I used to use a hand file in a vice as you are suggesting and it works just fine, or vice grip it to a surface if you dont have a vice. Angle grinders are super affordable, I recently bought an extra so I dont have to change discs as often during projects and was surprised by the low cost.
 
I use a 4 1/2” angle grinder, a file, and a large step drill bit.

I just put the blade in a vise and start by grinding the cutting surface making sure to take any nicks out and profiling them. After that I take a flat bastard file and clean up the backside, then lightly go over the cutting edge with the file.

I then place the blade on the large step drill bit to check balance. Sometimes you have to go back and touch up to get it as close to balanced as possible, but if it’s close I don’t obsess over it. I’ve had brand new, off the shelf blades that weren’t perfectly balanced.

By the way, they don’t have to be “shaving sharp”. As a matter of fact, if they are, the sharpening won’t last as long.

Edited to add: I always have a spare pair, sharpened and ready to go hanging in the shop. I clean them up with a rotary wire brush, paint them flat black, and write the date they were last sharpened on them with a silver Sharpie.
 
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