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blade sharpening


toad270

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How do you sharpen your mower blades and what angle should they be? I use the bench grinder then hand file.
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I sharpen mine with a 4" angle grinder, at about a 45-50 degree angle. Sharpen a lot because of sand.
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I have a dedicated blade grinder I use, but then I work on mowers for a living. I generally set my grinder to sharpen at about a 50 degree bevel. The wider the bevel, the better the blade will cut, however the "edge" will dull quicker and need sharpening sooner. A narrower bevel will last longer, but won't cut quite as easily. The most important thing to remember when sharpening blades is to balance them. I can't emphasize that enough. Your spindle bearings and housings will thank you with much longer life! If you don't have a balancer, buy a cheapie cone-type. I can get the cone-type for only $3-$4. Even a big nail driven into a post is better than nothing, but whatever you do, balance your blades.
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I always start by grinding/filing at 90° till the nicks and wear are gone, that gives me a good and quick way of teling if the blade should be trashed or sharpened the rest of the way. I use a bench grinder, then a 4.5 inch angle grinder, then finish with a file. I skip steps depending on the condition of the blade or if I where real steady on the bench grinder. Some just need a file some need a little more help and others (that probably shouldn't be sharpened in the first place) need a lot of help. I try to follow the original angle as close as possible if undeterminal I go with 45°.
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Amen JR! Out of balance blades are not only hard on the equipment, but the operator may suffer for the ride, as well. Severely out of balance blades will make a tractor shake while the deck is in gear. I normally sharpen at about 45 degrees, makes the blades last longer, but sharpen the finish mower blade at 50 degrees or sometimes more, depending on the mood, and the way the last person ground it. I also use a bench grinder, and always grind one side, never sharpen from the back side of the blade, as I have seen a lot of others do.
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I have seen no mention of bent blades. Most have to be straight within 1/4". How do you handle that?
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I'm pretty hard on my blades from small debries in the yard. Howevr, I try not to get near gravel and other mess that may nick or damage them. If I think I can grind it up I'll go for it.lol I do sharpen often and always grind into the edge, not towards the edge. I think sharp blades cut better, cut faster, and cause lots less wear on the belts, and the engine.
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Bent or cracked blades get trashed unless it's just a little tweak. Best way to check is on the deck, mark where one side is on a spot on the deck then spin the other side to the same spot and see if it matches (you be surprised that what looks straight off the deck will be bent on the deck). To check for a tweaked deck/spindle mount I use a straight edge across the blades when they're lined up.
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I agree with JR, got to make sure they're balanced. I use a cheapie plastic cone set up. It may not be "cutting edge" (pun intended)technology, but on my handmower I use for trimming I noticed a lot less vibration, so I balance all my blades. How do you measure the angle in degrees? I always try to duplicate the factory bevel angle with my bench grinder then finish off with a mill bastard file for a razor-sharp edge. For me the only place for bent, broken or worn out blades is the bin at our local recycling center. Brian
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All good tips above - definitely start by grinding the edge flat to remove any nicks and taper from the center out to the end of the blade. The cutting edge should be parallel to the centerline. A rounded corner out at the end is what will lead to leaving a strip of uncut grass - you lose blade overlap when the blade gets worn off or ground wrong there. Some decks are more prone to this than other due to design - will be noticed more during a turn. If possible, follow the original bevel. Any blade that has the lift, or wing tip worn off or cutting back is junk - that metal is wearing off and could actually tear away. Finish the grind with a hand file - the actual edge only needs to be about 1/16 tall. If left raw from the grinder - that could tear grass and lead to turf problems. A rounded off dull blade only beats the grass apart, doesn't cut it off. Also, with the balancing - if you bother to do it, make sure you have a clean blade - any grass build up will throw you off. So, mowing in wet grass is out then, because the wet stuff that clumps up on your blades just defeated your well spent time on your blade. Last, but not least, properly torque your blades back on. Never under-estimate the power of your mower deck and the harm it can do from misassembly, damage and abuse. Tim
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Anytime I work on a mower where I find the lifts to be undercut or worn to a sharp edge, those blades get replaced. No hesitation! I don't send a mower out the door that I don't feel is safe. It's just not worth the risk. I had a Crapsman in the shop a couple of weeks ago that actually had holes worn into the blades! These folks have very sandy soil, and that's the worst thing for blades. It's like the blades are being constantly sandblasted. Of course it's not real good for decks either......
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