MTD walk behind front propelled just leaves clumps on right side

My 9 y.o. MTD walk behind mower just will not mulch at all and leaves lines of clumped clippings everywhere I mow, for any cutting length greater than, oh, maybe an inch or two.
Is this possibly remedied by getting a new blade and not simply sharpening my old one over and over? I'm suspicious that my dremel tool sharpening of the old blade is not maintaining the precise curve it once had. Does that matter?
I may be getting a new mower---hence my companion post in this ng.
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"Thomas G. Marshall" wrote:

http://personalpages.bellsouth.net/t/h/theplanter/Farmer-workshop.html
sharp blades are a very important part of maintaining healthy lawns.
http://personalpages.bellsouth.net/t/h/theplanter/blades.html

Snapper 21 inch self propelled. converts between side discharge, mulcher or rear bagger. I've been running the Snapper now for 4 years in my lawn care business and the Snapper performs very very well. they are expensive. like $579.00 and you can't buy one at those crap stores like home depot or lowes.
http://snapper.infonow.net/bin/findNow?CLIENT_ID=SNAPPER_USA
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