As the title suggests, how sharp is ideal on a lawn mower blade? Does anybody sharpen new blades?
How sharp is too sharp? Sharpen new blades?
- Thread starter buck91
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Some people shave brand new tires, so not impossible.
On the professional forums there is not a consensus on this. Generally, mower blades are sharpened at approximately 30 to 33 degrees. Some finish the edge to a sharp point, others finish it to a more blunt edge.
Here is Oregon's stance: "Mower blades should be aggressively sharp, but not as sharp as a razor’s edge. You should be able to touch the blade with your hand without getting cut. Contrary to popular belief, a lawn mower blade with a razor sharp edge will not cut grass better. In fact, an edge that is that sharp has the tendency to roll over, which can cause blades to get nicked and chipped. Additionally, lawn mower blades that are too sharp get duller, faster resulting in the need to sharpen more frequently and a shorter blade life."
"All Oregon blades, are ground at 30 degrees. "
www.oregonproducts.com
Here is Oregon's stance: "Mower blades should be aggressively sharp, but not as sharp as a razor’s edge. You should be able to touch the blade with your hand without getting cut. Contrary to popular belief, a lawn mower blade with a razor sharp edge will not cut grass better. In fact, an edge that is that sharp has the tendency to roll over, which can cause blades to get nicked and chipped. Additionally, lawn mower blades that are too sharp get duller, faster resulting in the need to sharpen more frequently and a shorter blade life."
"All Oregon blades, are ground at 30 degrees. "
How to Sharpen a Lawn Mower Blade | Oregon Products
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As sharp as a new blade, which is surprisingly dull. Balance is important. Don't sharpen if you can't balance it reasonable well.
Sharper is better for grass. But if you have twigs, small rocks or other debis, sharp thin edges will form gaps and become dull faster.
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Sharpen to a nice uniform edge of about 30 degrees but not in any way like a knife. A fine edge damages easily as noted in the oregon post above.
John Deere suggests 1/32 blunt edge on their blades.
for personal use on your lawn they should be sharp. Your lawn that you know, no rocks, dirt, ant piles. But if you are doing it for commercial use they should not be sharp because you never know what your blade is going to catch.
[QUOTE="I Usually just a couple passes with the grinder, they don't need to be razor sharp.
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Yup. No need to duplicate the angle or 'look' of the blade as it came from the factory. (Keep in mind the .000001% increased effectiveness of the blade by duplicating and angle will ensure you have to buy a new blade after 3 or 4 sharpenings instead of 10.) Run the grinder over the edge to get rid of the 'burr' and any nicks and put a decently sharp edge on it. Don't dwell on any one spot to get out nicks. One even, steady run of the entire cutting surface across the grinding wheel at a time until the nicks are gone. Don't turn the metal blue or you might (just might) take away some of its hardness. No it's not super, heat treated hardened, but it is bit harder than a regular piece of steel. Center the middle hole on nail driven into the wall and make sure it’s balanced. Then it will be sharpened and balanced enough. If you hit something hard and SLIGHTLY bend the blade, put it in a vice and bend it back. As with all things take your time and the sharpening (and bending) process will be a pleasant one.
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Yup. No need to duplicate the angle or 'look' of the blade as it came from the factory. (Keep in mind the .000001% increased effectiveness of the blade by duplicating and angle will ensure you have to buy a new blade after 3 or 4 sharpenings instead of 10.) Run the grinder over the edge to get rid of the 'burr' and any nicks and put a decently sharp edge on it. Don't dwell on any one spot to get out nicks. One even, steady run of the entire cutting surface across the grinding wheel at a time until the nicks are gone. Don't turn the metal blue or you might (just might) take away some of its hardness. No it's not super, heat treated hardened, but it is bit harder than a regular piece of steel. Center the middle hole on nail driven into the wall and make sure it’s balanced. Then it will be sharpened and balanced enough. If you hit something hard and SLIGHTLY bend the blade, put it in a vice and bend it back. As with all things take your time and the sharpening (and bending) process will be a pleasant one.
Good luck trying to do this! It is much better to pony-up for a replacement blade if you bend it.
Also, if you hit something hard enough to bend the blade you need to check the blade adapter, the crankshaft (for straightness), and the flywheel key.
You can't balance a blade this way. A proper blade balancer only costs a few dollars and can be purchased almost anywhere (Walmart, Home Depot, Lowes, Ace, True Value, Amazon, etc).
I put a really sharp edge on a set of my mulching blades last year out of curiosity. They really did well with the thick, wet spring grass but definitely dulled fast.
There is no point in putting an extremely sharp edge on a mower blade. You can think of steel for blades as having a triad of properties that must be balanced for the tools purpose. Hardness, toughness and strength. Drill bits and machine cutters need to be hard and strong. An anvil will be tough and strong. All three of these properties tend to be hard to achieve at the same time. For example, if you make steel really hard, then it tends to be brittle (the opposite of tough).
The most important property of a mower blade is toughness and the ability to hit objects without shattering and sending shrapnel all over the place. If you used a high carbon steel and tempered and heat treated a mower blade the same way you would a knife that takes a razor sharp edge, the first rock you hit would break the blade. So of necessity, mower blades will always dull quickly as they are relatively soft. There's no point in changing angles and putting a fine edge on one.
The most important property of a mower blade is toughness and the ability to hit objects without shattering and sending shrapnel all over the place. If you used a high carbon steel and tempered and heat treated a mower blade the same way you would a knife that takes a razor sharp edge, the first rock you hit would break the blade. So of necessity, mower blades will always dull quickly as they are relatively soft. There's no point in changing angles and putting a fine edge on one.
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Here is something that will mess with your mind but try it. Sharpen your blade, be it 30 degrees or razor sharp. Stand the blade straight up and run a grinder/sand disk lightly over the sharpened part of the blade. This will result in a squared off cutting edge which then creates 2 cutting surfaces instead of 1 if sharpened in the "Traditional Way". This will create an "edge" that will last a long time and will cut your grass like no other. Try it out and let me know.