Well, on my 1983 Snapper Hi-vac RER, i finally decided the blade needed changing. now, i always sharpened it every spring, so i decided after that long, an investment in a new blade would be proper. So, for around $20, i bought a new blade and installed it, with the up-lift wings, as on the old one! Wow, i thought--I'd cut the grass now, instead of snatching it off with that old blade! First time out, the blade smacked the edge of the housing and bent the edge up. Fixed that. Again, bent it somewhere else! fixed it, and fixed and fixed--ad infinitum. Finally got so disgusted, i hunted up the old blade, reinstalled it, and all is well again! I can't really complain, as the dealer friend gave me the new blade! (I have given him numerous Toro parts mowers, and other makes, so it was a sorta trade-off!) And, yes, i don't believe in buying something new, if i can keep an old one running!) Aww, it would be nice to have a big new green machine setting out front, but--i'd probably be tempted to put a for sale sign on it,. and go back to my old Snapper!

Take the spark plug wire off the plug and ground it. Turn the mower up on it's side with the carburetor on the high side. Take a piece of wood and block the blade - sometimes you have to hold the wood block by standing on it. Using a long ratchet handle or breaker bar, put your weight on it and break the nut loose. Yes, counter-clockwise is right (also 'lefty-loosey, righty tighty').

I say 'knife sharp'. New blades are dull for liability purposes. The durability of the sharp edge argument is invalid, because once the edge wears down to the new equivalent, it will then still cut as well as a new blade. In the meanwhile, though, it will cut a lot better than a new one. I like to hear the 'hiss' of a really sharp blade hitting the grass, and there's no doubt the cut is better. I sharpen my blades with a 10" flat file, with the blade in the vise. If I go too long and the edge gets beat up, I'll use the bench grinder to re-shape it. There is no 'ultimate test' for sharpness. Looking at the sharpened edge, you should see no reflection. A reflection from the edge indicates an area that needs more attention. Make sure to maintainthe original edge angle, keep the edge straight and avoid setting it back at the starting point closest to the hub - the correct way is to gradually angle the edge over time, not keep it parallel to the back of the blade. This avoids setting up a stress point at a 'corner'. When the end of the blade gets down to 1" width, throw it away. In reality, the high-lift back edge will be worn too thin long before that.

You'll notice 'airfoils' on the blade behind each cutting edge. These are there to pull the grass up for cutting. They generate a large volume of air flow just like a 'bagging' blade, but also chop up the clippings/leaves a little when bagging so you can get more area of the lawn done before dumping the bag. A blade without the mulching 'teeth' will perhaps generate more air but doesn't chop as well.