lawn mower blade


Old 07-19-01, 06:26 AM
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Is there a special way to sharpen a mower blade? Can you use a file?
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Old 07-19-01, 07:01 PM
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Hello kdblais

A file could be used but it usually takes much too long to complete the task and it is also too much work.

Best two methods would either be a belt sander using a 100 grit belt or a ginding wheel.

If you'll check within the archives of this forum, there are several prior postings on this topic. Also included are several methods to balance the blade after sharpening it.

Once the blade is sharpened, it must be balanced. Failure to do so will cause vibration and excessive wear to the lower crankcase seal. If it becomes damaged, the engine will begin to leak oil.

To help you save some time going back into the archives, below are several methods to balbe a blade.

Blade balancing methods:

A prior posting asked for a discription of the professionals rotary mower blade balancing tool.

With the useage of some visionary imagination and a text only discription, I think I can explain and you will understand the simplest sharpeners rotary mowers balancing tool.

Picture a number 8 size wood nail pointing vertically upwards with a metal pedestal base about 3 inches round. Then picture a tapered cone about 3 and 1/2 inches round and 3 and 1/2 inches high.

The metal cone is very pointy at the top and has a smooth inside diameter. The cone has several circled ring stepped outside diameters. Each of the several rings is the exact diameter of one of several mower blade center hole diameters.

When the cone is placed on the point of the nail and the mower blade is placed onto one of the cones rings, the blade will balance on it's center point. If the blade is balanced, it will be perfectly level. If not, it will lean to the heavier side.

Additional methods the homeowner can use.

Picture a 12 penny nail placed horizontally in a shop vise. Place the hole in the lawnmower blade on the nail, and the blade horizontal. The blade will tip or tilt towards the heavier side.

Place a small triangular file in a shop vise, with one flat side of the file facing the floor. Place the hole in the lawnmower blade on the file, and the blade horizontal. The blade will tip or tilt towards the heavier side.

Place a plumb bob pointed side up in a shop vise. Set the lawnmower blade on the plumb bob, similar to your step-tapered cone.

Use a dowel center that has the same size hole as the hole in the blade. Insert the dowel center in the blade hole, and put the pointed side on the head of a roofing nail which has been inserted vertically in a vise. The blade will tip or tilt towards the heavier side.


An out of balanced blade will cause vibration, excessive and rapid crankshaft seal wear. The later will cause an oil leak to appear first, then bearing failure.

A severely out of balance blade is also potentially dangerous to the mower operator. Any blade revolving at high speed can become hazardous. The vibration will also loosen other parts on the machine and tire the hands and arms quickly.

Good Luck,
Sharp Advice
Accurate Power Equipment Company.
Small Engine Service and Repair Technician.
Personal Quote:
"If it ain't broke, don't fix it until it is broken!"

Last edited by Sharp Advice; 11-06-05 at 06:34 AM.
Old 07-20-01, 05:20 AM
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Thanks for the helpfull information Tom.
I'll start tonight

Old 08-15-01, 10:57 AM
some help
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only the first 2" of the blade on each end need to be sharp to cut a good lawn. Replacement blades can be found from $5.00 up.....I use a good "******* file"and touch up the blade as needed, unless you are cutting a rock pile this should do it. just follow the angle on the blade. If you should need a heavy sharpening you will need to do as Tom has said or send it out, always keep a spare "sharp" blade. Good Luck ....

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