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Old 12-15-2002, 07:00 PM
Doogiegh Doogiegh is offline
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Join Date: Oct 2001
Location: Central N.J.
Posts: 877
Blade tip speed on a 21"

Does anyone know the typical blade tip speed on a 21" mower, say a Toro 21" or a craftsman 20-21" homeowner grade stuff?

And lets say you are using blades that are 18 inches long.. How "MUCH" of the blade do you think actually does the cutting? The outside 4-5 inches on each end? so the middle 8-10 inches near the center hole really don't do much cutting, right?

How far down the ends do you sharpen? Gonna do some math on your numbers.. Thanks

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Old 12-15-2002, 08:07 PM
Bob Minney's Avatar
Bob Minney Bob Minney is offline
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Join Date: Jan 2002
Location: The Hottest driest city next to Hades - Denver Colorado
Posts: 1,094
My ariens 21" approx 18,000 fpm @ 3,000 rpm
OEM blade has 3.5" cutting edge
Gators 5"
If you want people to notice your faults, start giving advice.
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Old 12-15-2002, 08:50 PM
barnard barnard is offline
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Join Date: Jul 2002
Location: central,OK
Posts: 618
It's easy to figure on a walk behind with the blade attached directly to the crankshaft. Formula is blade lengthX3.14Xengine rpm. Example with 21 inch blade and governed engine speed of 3,600 rpm. 21x3.14=65.94 round to 66 this is inches traveled at blade tip in one revolution of engine. convert to feet by dividing by 12. This is 5.5feet per rev. Times 3,200=19,800fpm
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Old 12-15-2002, 08:51 PM
Likestomow Likestomow is offline
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Join Date: Feb 2000
Location: Tennessee
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I only sharpen the outer 1.5" of every blade I use.
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Old 12-15-2002, 11:55 PM
Lawn Specialties Lawn Specialties is offline
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Join Date: Nov 2002
Location: central Il
Posts: 205
Advertised blade tip on a Toro 21" is 18500. I sharpen mine same as they come from the factory but have thought of going in further. Any body tried it?
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