My mowing needs are not for a lawn, but to keep the weeds down. As far as I can tell, (much as I've already concluded for the mulching blade on my weed whacker), it is the mass of the blade and the momentum/velocity exerted by the machine that cuts, not how sharp the blade is. I can understand the need for a sharp blade if your goal is to have a putting green, but that's not what I've got. Figure I'll just leave the old blade in, dull as it is, and as long as it's destroying weeds, job done.