lawnmower blade

[redskygroup]

i have a craftsman 3 blade ride on mower and one day after mowing a field of tall grass i turned the blades off, the center blade just fell off the shaft onto the ground. i just thought it a fluke wierd thing, so i sharpened the blade and took the other two blades off to sharpen and balance them as well,then put them back on. excited to mow with sharp blades i started her up and took off for the field.it worked perfectly. i mowed the field and when finished i shut the blades off only to find the end blade had droped off the shaft. i thought perhaps i had not tightened the bolt enough, so i torqued it down as much as i could. just to find that on a trial blade run it does the same thing. quite frusterating- i cannot find anything on lawnmower blades just falling off. does anyone have any suggestions???

[Lou]

Asked Sears?? Mounted wrong side up??

[redskygroup]

i thought so at first, but checked immidiately, and that's not it. i wondered if perhaps the blades were clipping each other causing one of them to unscrew the bolt, but there seems to be clearance. thanks though-

[Oscar_Lives]

Put some red Loctite on it.

[jwn]

[Timothy]

If the blades made contact, you and the rest of the neighborhood would know for sure! The noise and the resulting damage would be quite obvious. The bolt should never "loosen" up by it's self. The bolts always (in every mower I've ever had) screw down the opposite direction of the blade spin. So in theory the bolt should tighten while the blade spins.

I asked my toro guy about the bolt loosening up and that's what he said. Then he took me out back, hand tightened my blade bolts, started the blades for a mineut and shut it down. He lifted the deck and I checked the blades and they were on good and tight. I needed a socket set to get them off again. By no means should one do this to install the blades, but the exercise was all about showing me that the blade bolts are ment to self tighten and if I screwed up the blade install I should be safe.

I would suspect that you have a bad bolt, a bad spindel or bad blade. Look to see if the bolt has been striped or is worn somehow. Mount the blade and see if the blade is bent. A bent blade could vibrate the bolt off. Last, inspect the spindel to ensure that the threads are not damaged and the spindel is not bent.

[Tom J]

If it is belt drive with a twist in the belt, a wrong twist would cause 1 blade to go in the wrong direction. The belt on that blade needs to be flipped. That's my guess. Tom J

[Tomes]

I would get a new set of bolts to eliminate that as a variable. They are cheap. Tomes

[ds549]

have had that problem on push mower,went with grade 8 bolt ,lock washer and heavy thick washer.

[Tom J]

believe the belt is twisted the wrong way and running the blade in reverse.

Tom J

[ds549]

grade 8 bolt brittle???? now thats a nrw one..

[Chas Hurst]

is required, use a military spec bolt. Or use grade 5, which is sufficiently strong and much more ductile.

[Stubby]

The manual for my mower says to use grade 5.

[Tom J]

didn't have a clue about the use of different grade bolts. I suggest you read up on metal grades before suggesting someone switch bolts on anything. The one thing I've seen the most mis-used in my years as a mechanic is grade 8 bolts.

Tom J