Sharpening Blades

Auto Doc's said:
Way too much sand in my area, I seldom sharpen blades. Most have the lift area sandblasted badly or they are starting to crack. Even if they could be sharpened, they would not be safe enough to keep using them.

Ebay to the rescue for most of my blade needs unless the customer wants to pay big bucks at the local hardware store.
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I have been seeing a surge in that exact air lift cracking. sandblasted groove cut into the air lft the past few years. Seems a lot more common than years past. I don't know what has changed.
 
Metal quality is down. They are using cheaper metals to keep the sale price down and actually end sell more because of it.

You tell it by how easily the blades are sharpen now. High quality steel takes longer to reshape.
 
Tiger Small Engine said:
My question refers to customer mower blades. Many of the blades I see on customer equipment are really dull and beat up. It is not uncommon that I have to reestablish the angle and depth on cutting edge the blade is so bad. It can take 15-20 minutes per blade to sharpen correctly. I am not asking about how the blades are sharpened. We all have our preference. Are you guys seeing a lot of beat up blades come in? Many of these people are lucky if they sharpen blades once a year. How much do you charge per blade? Also, not uncommon to see bent blades. I can usually straighten them without replacing.
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slomo said:
I still think a hand file is the best way to sharpen. Once you cross over into grinders, one can remove too much material. Course a lot of blades you shop guys see need grinders. Home owners like me, my blades clean up in a few strokes. Too much metal removed gets into heavy balancing tricks.

For me, going over to the dark side, thinking about a 4" angle grinder with a say 220 grit flap wheel. Got 5 mowers to tend to.

For balancing I use one of those precision food grade scales. Weigh each blade end a couple times. Can balance a blade out to 0.0X of a gram per side. My blades run super smooth like a new one. I tried nails and those plastic and metal cone balancer deals. Food scale is in another league.
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A 220 grit flap disc is not aggressive enough, unless you have time to spare. I use a 60 grit with a moderate amount of pressure.
 
Slomo, I don't understand how you are using the scale would you explain that a little better. I have lots of time on my hands and would love to try this.
 
Mowing the lawn is a chore to most people; so is mower maintenance. The thought of an oil change, scraping the deck, and the "health" of a mower blade is the last thing such a person thinks about.

To those of you who own shops.... how many blades are you sharpening each year? If it's several hundred then why not invest in a dedicated blade sharpener? It'll pay for itself the first year.

I don't own a shop, but I sharpen blades on the side and charge $10/blade for a single blade. I offer discounts for multiple blades, but the first time I see any blade it's $10 just because it's going to need more work to get back into shape. A typical homeowner OEM Toro Recycler blade is $20+, so they're saving over $10 or 50%. A 3 blade set of commercial blades can be close to $100. I picked up a commercial customer last year who hates sharpening blades. He drops off 2 sets of blades every other week and is happy to pay me vs. buying new blades.

A few other things....

All bets are off if a blade is being used in sandy soil. I've seen pictures of blades that have been sandblasted to death and have basically disintegrated.

If a blade is visibly bent, don't try to straighten it. It's been compromised; just sell them a new blade.

I don't understand using a scale to balance a blade? Weighing one side at a time.... but where is the rest of the blade at when one side is on the scale?
 
Tiger Small Engine said:
My question refers to customer mower blades. Many of the blades I see on customer equipment are really dull and beat up. It is not uncommon that I have to reestablish the angle and depth on cutting edge the blade is so bad. It can take 15-20 minutes per blade to sharpen correctly. I am not asking about how the blades are sharpened. We all have our preference. Are you guys seeing a lot of beat up blades come in? Many of these people are lucky if they sharpen blades once a year. How much do you charge per blade? Also, not uncommon to see bent blades. I can usually straighten them without replacing.
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I think you got a lot of advice about how to sharpen so I'll take the root cause question you asked. The Brinnell hardness of the steel used these days is far lower than the blades from years ago primarily because of some mistaken belief that a 19000 ft per minute tip speed, softer blade, won't inflict as much damage to human limbs and will "give" rather than cut. Yeah. Right. Same goes for limiting damage to the drive train. If it hits a T post stub there won't be much give. Mass and velocity rule the day.....hit that T stub with an 8ft brush hog and you'll never even feel it slice through....unless it takes the more direct route and just yanks what's left out of the ground. But then it just gets really noisy for a bit til it spits it out.

If you want the blades to really last you'd have a couple of beads of high tensile, low hydrogen steel welded to the cutting edge and then establish the angle and edge....but that also brings liability issues should someone be injured. So most don't. They just throw away blades regularly and replace.
Tiger Small Engine said:
My question refers to customer mower blades. Many of the blades I see on customer equipment are really dull and beat up. It is not uncommon that I have to reestablish the angle and depth on cutting edge the blade is so bad. It can take 15-20 minutes per blade to sharpen correctly. I am not asking about how the blades are sharpened. We all have our preference. Are you guys seeing a lot of beat up blades come in? Many of these people are lucky if they sharpen blades once a year. How much do you charge per blade? Also, not uncommon to see bent blades. I can usually straighten them without replacing.
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Nice thread! A lot of good info. I have a little tear in my eye from the camaraderie. 👍

Most blade sharpening instructions I have seen specifically mention rounding the sharpened edge somewhere between (IIRC) 1/32 and 1/16 radius. I'm thinking that an advantage to that is less inadvertent nicking. Also less total removed metal (and time) to maintain the proper wedge angle with slightly rounded but "perfect" edge (i.e., all nicks and other imperfections removed).

So, I'm thinking longer blade life, maybe quicker sharpening job - and, as others mentioned, it's going to quickly more or less wear close to that in a matter of less than an hour of cutting time.

Also - by educating the the public to accept slightly rounded new edges, blade manufacturers see a plus of less risk (liability) of some customer or their kid getting a deep cut from intentionally or inadvertently dragging a finger tip or other body part along an exposed edge in the store or otherwise before installation.
 
I know this isn't going to go over worth a crap, but I use a bench grinder. I do about the same amount on each side, and my blades have that bend in them to increase the lift. It takes maybe a minute for each side or less and I've never balanced them once I'm done. Been doing it that way for 25 years and it works ok for me, but maybe I'll try some of these other methods folks have mentioned here. Angle grinder sounds interesting. Cheers and don't forget eye protection!
 
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