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blades loosening during use


MrSteele

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I finally got the tractor going, replaced the rollers and belts on the deck, bought a set of blades, beat out the worst of the dents and straightened the warps. Now, you'd think I was ready, right? I used the mower briefly last week, and the far left blade simply fell off during use. That is one of the mandrels that has a bolt in the center and a splined shaft. The blade unscrewed the bolt as far as I can tell. The nut on the center shaft above the drive pulley refuses to stay tight, as well. I know what I'll do about the nut, but why won't the blade stay tight? I replaced the blade this afternoon, used it a bit to see if it was ok, and it was loose quickly. With exception of removing the deck and using an air wrench to nearly strip the bolt in the hole, is there another way to keep it tight? I like being able to remove the blades for sharpening without removing the deck each time, so I hesitate to use the air wrench method. Any others with a similar problem? And the strange thing is, the right blade is also on the same type of mandrel. It stays tight, and I gave each about the same amount of torque.
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I think (not sure) that these types of spindles use a dished washer to hold them tight. You put the "cup" of the washer against the blade and torque the bolt down. This "cup" flattens out a little and keeps pressure on bolt head to keep it from turning... Again, I may be mistaken, but I think that's how they work...
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You probaly have a flattened Bellvue washer. These are special cupped washers that clamp done on the blade when you tighten things down. You didn't supply model number, age and or type of machine, but this is my gut feeling.
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I had the same problem on my AC 710. Order new cupped washer, I get mine from Sandy Lake, use a good fresh lockwasher, and tighten with air impact if you have it. This solved my problem. Oh yeah, a little dab of loc-tite on the bolt threads probably would help too.
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Hi, Do you have the spline washer in the splines and not butted against them when you tighten the bolt? Would suspect the pulley has been run "loose" and the splines are bad in the pulley and maybe the top of the shaft. As mentioned be sure the "hump" in the washer is again the bolt and the edges of the cup against the blade. Al Eden
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Wasn't aware of the cupped washer. The splined washers are in place, but the blade simply does not tighten completely. Will solve this quickly. Thanks
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I never had this problem until about 3 months ago. My Dad has a little JD STX 38...hey all I do is use it;) and after sharpening and replacing the blades, one of the blades (2 blade deck) fell off. So, back to the garage and off with the deck this time to find the bolt had broken off not worked loose. A bit of drilling and an easy-out later I went to the JD dealer for a new bolt. When I asked about torque for the bolts and he laughed and told me they use impact wrenches. I replaced the bolt and re-used the washers and it's been fine ever since. I guess it was a case of bolt fatigue, but it was a first for me. I only make these bolts hand tight to save me having to drop the deck each time. Of course on my Simplicity machines, I drop the deck, sharpen the blades, grease the zerks and I'm back in business. As others here have said, check the washers and use a dab of lock-tite the stuff really works. If memory serves, the blue stuff can be removed without heat but the red stuff requires heat...gee hope I said that right.
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What worked... I removed the whole assembly again, turned both the cupped washer and the splined washer over, as the splined washer seemed to have a cup in it, as well, and now the blade stays put without the use of an air wrench. Something that I do not like about the left hand cut is that when tightening the blade bolt, pressure must be placed against the sharp side of the blade. Put a block of wood there to alleviate the chance of hand removal while tightening.
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