Sharpening blades (hit the back side?)

Discussion in 'Lawn Mowing' started by tacoma200, Oct 18, 2005.

  1. tacoma200

    tacoma200 LawnSite Fanatic
    Messages: 5,426

    After sharpening my blades a few times it gets hard to get a good edge because the bottom of the blade has wear. I a tempted to hit the back of the blade a few licks but I have heard you shouldn't do that. Not sure why. I would have to take off alot of metal if I only hit the top side. I use a file. I decided to take the blades down to the local lawn care shop to get them sharpened and to my surprise he hit the back side a few licks. Just wondering why you are or are not suppose to grind the back side or any other helpful suggestions. Some of the lots I mow are rough so i hit dirt, rocks, etc every now and then so I know I'm hard on blades. Any advice would be great. These are Exmark blades.

    TURF DOCTOR LawnSite Silver Member
    Messages: 2,138

    I hit the back side first thing then i sharpen to a razor.
  3. skidmaster

    skidmaster LawnSite Member
    Messages: 34

    Hi Tacoma it's me, skidmaster...... Some helpful sharpening tips starting with new blades. 1.Put blade in vice horizontally 2.I use a DeWalt 4 1/2 inch disc grinder with a metals disc (thin) 3.Keep disc flat to blade with only a left to right motion pressing gently until it is all shiny. Keep even strokes and don't bear down too hard. When it looks uniform flip it over in vice & make one or two passes very gently on outer most edge. 4. Flip that badboy over once more and make one very light pass over burrs. It should be sharper than shite. I have used this method for almost twenty years, My blades last a long time and the cut is very even and stripes nicely. P.S. Rocks and blades and or dirt mounds don't mix well. Better to clear property of hazards that beat on you and your equipment. So long Tacoma, skid....
  4. burns60

    burns60 LawnSite Senior Member
    Messages: 291

    I sharpen down the top side first all the way until I get a straight fine edge. Then hit the back side with a file to just get rid of the burrs. Don't do anything to the back of blade at an angle. Keep file or grinder flat on the back or you will sharpen both sides to an angle and this won't last a day. Nicks in the blade just get sharpened. If you try to grind them out you will unbalance the blade. On a really bad nick or chip from the blade, when I do the other end I grind out a nick at end of blade to keep balance.
  5. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    That's how I do it, but:
    - I started with the Dewalt grinder until 3 years later I needed to replace the disc and it will NOT come off. Evidently you need to take the disc off / put it back on about once/month or it fairly fuses itself in place. So until I figure out how to get the disc off, I bough a Chicago Electric grinder for 30 dollars and it works real good (and it's cheaper).
    - I would get the THICKEST disc possible, not the cut-off wheel but the grindind disc is about 1/4 inch thick. The reason for this is fly-apart issues, you do NOT want a disc flying apart on you at 10,000 rpm. Also the standard grinding disc is Type 27 and is a COARSE material. This is what I've been using but I am itching to find a FINE disc one day... Apparently Lowe's/Home Depot does not carry anything but Type 27.
    - When sharpening, watch for black spots appearing. When this happens it's because the steel is getting TOO hot. Practice makes perfect, over time learn to work it so as to get no black spots, when the steel gets that hot I hear say it skru's with the temper. Alas, even in my 4th year I still get a few black spots, so I do the best I can.
    - Instead of a vise, I hold the blade with my hand nowadays but when I first started this seemed too dangerous (dangerous it is but I like the 'feel') so then I didn't have a vise so I'd clamp the blade onto a flat surface of the trailer with a Vise grip :)
    - And yes, I always skim the bottom of the blade lightly, just a teenie touch to give it the edge. Always go easy, never grind hard.
    - Far as the angle of attack, I learned the disc wears with time and what I concentrate on is to wear the disc at the angle I ALWAYS want to grind and yes, it is almost flat but not quite. Once the disc is worn in, it has a nice angled surface around the outer edge which makes it a true pleasure.

    Some other tips:
    - To restore balance (such as when one side is heavier), it is recommended one grind a little steel off the high lift part (dang I forgot the name of that plane thing)... This is what *I* refer to as the 'back' of the blade, thou I've also learned sometimes just grinding off a bit of dirt restores the balance.
    - NEVER take burrs or nicks OUT, this grinds off way too much steel AND you have to shave off the SAME amount of steel off the other side or your blade is off balance. Instead, I let burrs/nicks work themselves out over time and I place burred/nicked blades in the CENTER of the mower as this position is the most protected (on my mower, the outer blades generally catch the most hell).
    - Remember (get the info) critical wear, this is the point where a blade has been sharpened so many times, it is no longer structurally sound. Specifically, there isn't enough steel left to guarantee the blade will not fly apart should you hit an object but I get at LEAST a year's use out of ONE set of blades used FULL-time before I even worry about this. After the blade reaches this point (the manufacturer/dealer has the specs info), I continue to run these past-worn blades on my OLDER mower as the old machine turns out far less rpm's and the old machine is used mostly for the bush hogging (so to speak) so it doesn't bother me if it ruins a blade.
  6. Varsity L&G

    Varsity L&G LawnSite Senior Member
    Messages: 418

    Maybe someone would like to take some pics in the off season and put together a how to on blade sharpening and maybe Sean could make it a sticky somewere on here. I see all the time were others are asking how to do this and what works best.
  7. KathysLGC

    KathysLGC LawnSite Bronze Member
    Messages: 1,345

    I only hit the back side if there is a nick in the blade. All I do is get the back flat again. When I sharpen the blade there is no need to hit the back side. The blade is a single edge. You might have to shorten the bevel when you sharpen.
  8. Runner

    Runner LawnSite Fanatic
    Messages: 13,497

    Just like it was mentioned above, you should NOT grind the backside of the blade, as this can and will make a reverse angle that will counter the lift of the blade. The cut won'y be quite as clean and easy, as the angle can possibly contribute to pushing the edge of the grassblade down. When there are burrs, and to clean up the backside, a file should be used and run RIGHT LEVEL to the back of the blade.
  9. MBDiagMan

    MBDiagMan LawnSite Senior Member
    Messages: 852


    Now THAT makes sense.

  10. tacoma200

    tacoma200 LawnSite Fanatic
    Messages: 5,426

    Thanks for all the info. Some great ideas. Skidmaster, the rough lots go with the territory here in Southern Kentucky. There are some nice manicured lots but alot are very rough. You just have to work with them the best you can. I'm sure the lots in R.I. are much nicer on average. Its kinda like the guys from Australia say, the lots down here are much different than the ones in R.I. on average. Steep banks, dips, rocks on the surface, gravel drives that work out into the yards. No way to completely clear them. Thanks for all the good advice guys.

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