Anonymous Poster
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HELP, What is the best method and equipment to sharpen MMM dull blades at your home shop???
Mowing MMM mower blades
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Bird
Rest in Peace
KG FARMS, I just use an air impact wrench to remove the blades and sharpen them on a bench grinder being sure to take about the same amount off each end of each blade for balance. I check the balance by laying the center of a blade across a smooth round rod or screwdriver. Of course, I remove the mower deck and turn it over, or stand it on edge against a tree to get to the blades.
Bird
Bird
ronjhall
Super Star Member
KG Farms
Here is a post from another site.
My owner's manual recommends that each time blades are sharpened location of the blades should be changed to equalize wear.
I have always removed blades from mower for sharpening.
First clean the blade of grass buildup. If left on it will throw off the balance of the blade.
A bench mounted grinder is the easiest way to sharpen the blade but you can mount the blade in a vise or clamp to a table and use a drill motor grinding attachment or a big file. In any case, remove material from the engine side of the blade only. You'll see an existing bevel and that is where you want to grind. Approximately at 45 degrees. DO NOT remove material from the grass side of the blade. The cutting edge has to be the lowest point and if you grind on the bottom side of the blade it will bevel up and cause the bottom of the blade to drag and beat the grass. This will render your sharpening job useless and put an un-needed load on the engine. When you have a good edge on the blade a light, flush deburring on the bottom is ok, just don't bevel up. Next take a screwdriver or anything with a round shaft, which fits, easily in the center hole of the blade. Hold the screwdriver horizontal and hang the blade from it also horizontal. If the blade remains horizontal it's balanced and ready to go. If it wants to swing down on one side, that side is heavy. Go back to the grinder and remove more material as you did when sharpening. Make four or five passes, debur the bottom and check again for balance. Continue until the blade remains horizontal.
Re-install the blade and be sure the blade is back in the correct position. Torque spec varies and most homeowners don't have a torque wrench, but to be sure, it has to be tightened a bunch. Don't slip off and get yourself hurt but don't be a wimp about it either, It has to be tight.
Here is a post from another site.
My owner's manual recommends that each time blades are sharpened location of the blades should be changed to equalize wear.
I have always removed blades from mower for sharpening.
First clean the blade of grass buildup. If left on it will throw off the balance of the blade.
A bench mounted grinder is the easiest way to sharpen the blade but you can mount the blade in a vise or clamp to a table and use a drill motor grinding attachment or a big file. In any case, remove material from the engine side of the blade only. You'll see an existing bevel and that is where you want to grind. Approximately at 45 degrees. DO NOT remove material from the grass side of the blade. The cutting edge has to be the lowest point and if you grind on the bottom side of the blade it will bevel up and cause the bottom of the blade to drag and beat the grass. This will render your sharpening job useless and put an un-needed load on the engine. When you have a good edge on the blade a light, flush deburring on the bottom is ok, just don't bevel up. Next take a screwdriver or anything with a round shaft, which fits, easily in the center hole of the blade. Hold the screwdriver horizontal and hang the blade from it also horizontal. If the blade remains horizontal it's balanced and ready to go. If it wants to swing down on one side, that side is heavy. Go back to the grinder and remove more material as you did when sharpening. Make four or five passes, debur the bottom and check again for balance. Continue until the blade remains horizontal.
Re-install the blade and be sure the blade is back in the correct position. Torque spec varies and most homeowners don't have a torque wrench, but to be sure, it has to be tightened a bunch. Don't slip off and get yourself hurt but don't be a wimp about it either, It has to be tight.
Bird
Rest in Peace
Much better, and more complete, response than mine, Ron./w3tcompact/icons/frown.gif I forgot to mention that my bench grinder has a stone on one end and a wire wheel on the other, so I clean the blades throughly with the wire wheel before sharpening. And of course I only grind down the side that's already been ground down (top of the blade or existing bevel, as you said).
Bird
Bird
rbargeron
Elite Member
I find the quickest way to sharpen my blades is to use a hand-held electric grinder - an angle grinder like Makita etc. (uses 4" abrasive wheels). It's very fast - more effective than my bench grinder which has finer grit wheels.
Some advice I got a long time ago - no need for a razor-sharp edge - actually about 1/32 to 1/16 flat face will work just fine and the edge will hold up much better. Also, on a mower deck, perfect balance isn't quite as important. On a walk-behind, where the blade is mounted directly on the engine's crank, balance is a bigger issue.
Some advice I got a long time ago - no need for a razor-sharp edge - actually about 1/32 to 1/16 flat face will work just fine and the edge will hold up much better. Also, on a mower deck, perfect balance isn't quite as important. On a walk-behind, where the blade is mounted directly on the engine's crank, balance is a bigger issue.
OP
Anonymous Poster
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Gentelmen: thanks for the advise and hints.
Still how do they get the perfect Hollow ground bevel on one dide of the blade at the dealers shop?
Anybody knows?
Still how do they get the perfect Hollow ground bevel on one dide of the blade at the dealers shop?
Anybody knows?
djradz
Veteran Member
The shop I took mine to once years ago got the hollow ground by using the 4"/4-1/2" hand held electric grinder described above. The radius of the wheel produce the hollow. Shorly after that I bought my own Dewalt one and have been sharpening my own ever since. Even a large bench grinder cannot compare to the speed and accuracy you'll get with the hand grinder. Keep the grinder moving so you don't overheat and temper the steel. There is less chance of this with the hand grinder but it still is possible near the edges.
Just recently I bought another larger 7" Makita hand grinder for sharpening the blades on my Woods brush hog. Using the hand grinder I have never had to modify the sharpening to obtain balance, but primarily just eye-balled it. I do have a little cheap mower blade balance so I can check any that are questionable. Because there is so much steel and grinder wheel dust created when sharpening, not to long ago I bought one of those cheap folding "Workmate" type benches (around $20) that have a top which can clamp stuff, and now clamp the blades in that and do all my sharpening outdoors. Lastly, on your mower blades, if your looking for a fine finish to the job, and not apt to hit a bunch of stones or dirt, I finish the job off with a large medium-toothed file. The file cleans up any burs and produces an extremely smooth and level edge. I think once you try this method you'll be sold. Good luck and be careful, you'll get an extremely sharp result.
Just recently I bought another larger 7" Makita hand grinder for sharpening the blades on my Woods brush hog. Using the hand grinder I have never had to modify the sharpening to obtain balance, but primarily just eye-balled it. I do have a little cheap mower blade balance so I can check any that are questionable. Because there is so much steel and grinder wheel dust created when sharpening, not to long ago I bought one of those cheap folding "Workmate" type benches (around $20) that have a top which can clamp stuff, and now clamp the blades in that and do all my sharpening outdoors. Lastly, on your mower blades, if your looking for a fine finish to the job, and not apt to hit a bunch of stones or dirt, I finish the job off with a large medium-toothed file. The file cleans up any burs and produces an extremely smooth and level edge. I think once you try this method you'll be sold. Good luck and be careful, you'll get an extremely sharp result.
fishman
Veteran Member
Djradz,
That sounds like good advice. I think I'll try your method. Any excuse to get a new tool!/w3tcompact/icons/wink.gif
That sounds like good advice. I think I'll try your method. Any excuse to get a new tool!/w3tcompact/icons/wink.gif
Bird
Rest in Peace
John, I said I sharpen my finish mower blades on the bench grinder because that's the way I've done it for a lot of years. However, the shape of the blades (and the design of my 6" bench grinder) make it nearly impossible to do a good job on the brush hog blades, so I recently bought a new 4.5" electric angle grinder to sharpen the brush hog blades. It's a coarser stone than I have on the bench grinder, and it's turning more than twice the rpm, so it's faster (I have a 4" vise mounted on the work bench to put the blades in while I sharpen them), so I'll likely use the portable grinder myself in the future on the finish mower blades, too. Of course, you can also sharpen the brush hog blades with the angle grinder without taking them off the machine (don't know whether you have room to do that on the finish mower blades or not). And of course you don't necessarily need a real smooth finish like on a knife, but I frequently do a little finish smoothing on a bench mounted vertical belt sander.
Bird
Bird
