When to condemn mower blades?


Staff member
Dec 14, 2002
New Jersey
I’ve owned my Craftsman push behind for about 16 seasons now. I bought a second blade sometime in there.

I sharpen/swap the blade with its alternate at the start of the season, which is now. I’m not sure if these blades are worth/worthy of keeping.

I sharpen them with an angle grinder to be “uncomfortably sharp”. Not something you would want to hold, but not as sharp as a good kitchen knife or razor. The ends are starting to be scalloped inwards enough that it’s pretty obvious.

I know they’re not super expensive, but I like to reuse them if I can.

What’s the recommendation?

I'm somewhat frugal.
I would keep using them until 3/4 of width was left.

Good blades are inexpensive on E-Bay.

Having a sharp and balanced blade, along with changing the oil and cleaning the grass from underneath goes a long way.
looks good to me. I you plan to keep the mower for a while you could always buy a new blade now and compare it to the old to get an idea as to when to replace it.
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Thanks all. My primary interest/concern is if the scalloping inward of the blade was an issue or if I should consider to get rid of it.

Am I better off leaving the scalloped part, so long as it is sharp and balanced (how I have it now), or grind it straight?
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Why remove perfectly good iron. Use the blade as is, it'll cut fine.
Am I better off leaving the scalloped part, so long as it is sharp and balanced (how I have it now), or grind it straight?
I'm careful to keep the edge straight on my blades and balance them on a nail from the center in an attempt to see of they are balanced. I take a bit more off the edge that is heavier until the blade sits straight on a nail. This method isn't ASTM approved, but it works pretty well. :)

I'll add that I keep the edge straight, just because I do. I don't believe there is any functional difference between a straight edge and a curved edge.
I've had a Craftsman push mower about 15 years. Your blade looks better than mine and I haven't considered scrapping mine yet. I have only one blade which I sharpen it once a year with a bench grinder. They say to watch for grey tips on the grass blades as a sign the blade is too dull. I've never seen that.

It's hard to tell from the photo but it looks like you're sharpening the back edge too. If so, why?
That's exactly what both of mine look like. A quick pass on the bench grinder, and they're as sharp as a dull knife. I've always heard that making them that sharp just causes them to dull quickly, I just like to see how sharp I can get them....not a big deal to me.
I see no reason to replace them and do the same thing to new blades.
Looks very good keep using it. Mine get uneven wear patterns from the mulching grass that will eat a hole in ends before I change them. I went ahead and bought a second set of blades so I can always have a sharp set on hand. make sharpening less of a time consumer. Also good to have when you find a root or hill that bends a blade.
I also rotate a couple blades that I sharpen with a file. Still cut just fine at 18 years or so.
It has meat left, the real issue with blades are the ends. When they get too worn/rounded on the ends that is when you will start missing grass in between blades on a multi-blade deck, or it can give an un-even cut.

+1 on the back end of the blade looks like it was sharpened, which isn't needed. Is it some sort of reversible blade?

Also you don't want to sharpen the blade too much. It sounds silly but a blade that is sharpened like a knife will dull quicker. You want it to have a good clean edge (not round) but also not sharp enough to slice yourself with. The angle of the blade is what cuts the grass, not necessarily the sharp edge. Look at a brand new blade and you will see what I mean. A good clean edge all the way across is what you want. The curve on the blade isn't ideal, but will still cut okay.
I sharpen my blades and then blunt the front of the blade flat vertically,. Not a crazy thick square, but done until I can feel it as close to 90 degrees as I can, the flat edge having a thickness no greater the 1-2mm. Instead of the blade cutting at a 45 degree angle, its being cut at two 90 degree edges on the bottom and top. It maintains its geometry drastically longer than a sharp edge does, and I've never had a single issue cutting the grass with it.
I used to sharpen the edge to where it was about as sharp regular pocket knife, but I always found it to become dull very quickly.
Never understood why push mower blades wear more on the inside of the cutting edge and riding mower blades wear more on the outside edge.