Lawn mower blades

murraym said:
Does anyone use their milling machine to sharpen their lawn mower blades? I'm not thinking so much for the precision but it might be faster and easier to balance them removing the same amount from each side.
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I used to take the blade off. Now I just use a air die grinder and 1/4" shank stone. Takes me about 10 min. Al
 
Video_man said:
I use a belt grinder with a 180 grit belt. But I use a balancing device after to check balance and then fine-tune as necessary. I think maintaining the balance (which is important) is what you may be after with the equal-milling idea, but it would be difficult and time-consuming to do it that way.
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+1 on the belt grinder. Yeah, a fairly fine grit.
 
When I had my machine shop my neighbor shop was a welder and he used to weld hard face weld to the cutting ends of his mower blades.
 
murraym said:
Does anyone use their milling machine to sharpen their lawn mower blades? I'm not thinking so much for the precision but it might be faster and easier to balance them removing the same amount from each side.
Click to expand...

A lot depends on the mower. For me, I raise the deck, clip on the "transport chains" (safety chains I guess, which just hold it up when you're using other attachments), knock the blades loose with an air ratchet. That's fast and easy. Not all mowers are that easy). and sharpen with a flap disk on an angle grinder. I set the blade on a milk crate, 5 gallon bucket, the utility trailer, whatever, set one foot on it, and grind evenly. Then set them on a christmas tree balancer. The only time it takes ten minutes is if I've hit a rock, and have to anchor or wedge the blade, and get the hand wrenches to avoid sliced open arms.... (I'm in a clay area with 2 to 3 foot frost lines. Sometimes rocks grow up out of the lawn... I've been here twenty years, and this year I got a 500 pounder and a 200 pounder among the other. I thought I was done with those....).

Balance isn't something you feel. That goes to spindle bearing life. If you can feel a balance issue, you can count on you bollixed up a blade or two. The christmas tree balancers are more than good enough to keep bearing life to what it should be. Just like the removal process, a lot depends on the mower. If you've got overkill bearings (for pete's sake some of these things in the commercial range have preloaded tapered roller bearings....), then you could probably cut one side off each blade and cut your sharpening time in half without a compromise (except the shaking, that'll wear out your lift linkage...). If you've got a homeowner grade mower, balancing pays off big, but you don't really need to split hairs beyond the simplest methods to get a decent bearing life. If it sits on the tree kinda fairly level, you're good. And honestly, if you're paying attention to how long you spend grinding on each side, it's more of a check, corrections aren't that often, or that much.

Dont' split hairs when you're sharpening. A ding or a dent or one little spot that doesn't clean up- You don't care. If it wears back at the tip more then the center, don't try to straighten it. If the cutting angle gradually migrates to being too shallow, don't sweat it, just correct your angle on the very edge, and it's good. The blade, the mower, and the grass just don't care. Just so long as "most" of it is sharp, you won't know it from a brand new blade. It just drags on the process. smaller material removal, smaller out of balances (probably just a check, not a correction), the law of averages keeps 'em good from one sharpening to the next, and like I say, the need to adjust the balance becomes far, far less.


Could you do it in a mill? Pretty likely. Mower blades are funny. I never dug into what they (typically) are, but it kinda sorta a little bit acts like spring steel, and they crack where you weld 'em. They're not obliterated by welding, (as mentioned somewhere above) I know of folks who hard face them. I won't, but "allegedly" they don't crack if you do that. But they don't make good scrap steel structural things, as they crack by the weld. So I dunno, but I suspect you're gonna want a good cutter. Can you set that up with any kind of efficiency to beat out the time and effort it takes to sharpen them with a grinder? I doubt it, but maybe. Is it worth it to do it on a mill, because you have a mill, and you can overkill the crap out of something that really doesn't need it, and have mower blades cut to a thousandth of an inch precision and there's nobody around to stop you? Even though they bolt up to spindles that have 20 or more thousandths of play to invalidate all of your efforts? That sounds exactly like something I would do.
 
Flap Disc on an angle grinder and one of those plastic balancer things, been doing it that way for years.
 

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with 3M purple 80 grit belt. I remove the blades every other time to balance
 
It seems high lift blades are popular these days. After sharpening my diesel Z-Master Toro, I decided to try running it
a lot slower. I'm in sandy country so the high lift really eats on blades. I discovered three things:

1. The blades stay sharp a lot longer with way longer sharpening intervals.
2. I can mow 4 acres all season long on one fill of fuel.
3. The noise level has dropped considerably.
 
Thank you all for the replys. I understand it's overkill, i guess im just looking for an excuse to use the machines
 
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