Rotary Cutter Brush Hog Blades COMING OFF

MechanicalGuy · Aug 19, 2019

Grade 8 bolts should never be used in that application. Grade 5 are made for towing, suspension, steering and other life safety applications. Grade 8 should NEVER be used in safety applications unless specified by the engineer. Grade 8 break suddenly and without warning.

Asar2525 · Aug 19, 2019

MechanicalGuy, all replacement blade bolts sold that I have found are forged grade 8. I assume the engineers who designed these bolts know what they are doing.

MechanicalGuy · Aug 19, 2019

Asar2525 said:
MechanicalGuy, all replacement blade bolts sold that I have found are forged grade 8. I assume the engineers who designed these bolts know what they are doing.

I don't know, I was just warning of improper use. I have never seen a replacement kit specify grade 8. Even doing a quick glance on google, on several suppliers, none specifically call out the replacement as grade 8. Are you sure?

I see far too often people using grade 8 in towing applications and that is dangerous and should never be done. I don't know about bush hogging, but it seems like a tougher bolt would be called out. Hardened surface characteristics for sure, but tougher material construction than grade 8.

japody · Aug 19, 2019

Asar2525 said:
MechanicalGuy, all replacement blade bolts sold that I have found are forged grade 8. I assume the engineers who designed these bolts know what they are doing.

I have 2 sidewinders and have never had this issue. Are you sure that the bolts are put on facing up with the nuts on top? That way the spin of the blade tightens the nut as it spins. There should be a hole in the deck about a foot behind the wheel to access the nut. Here's my go to place if I have any questions or problems with my sidewinder:

Hercules Service Parts - Agricultural equipment repair located in Minden, Louisiana - Your Rotary Mower Experts!

Asar2525 · Aug 20, 2019

japody, yes the bolts are being inserted with the nuts on top of the blade mount. The blade spins freely on the shoulder of the bolt.

Fuddy1952 · Aug 20, 2019

I'm not a mechanical engineer by any stretch but over the years mechanical things designed like that are made so under stress like hitting a tree stump, rock, etc. would only make the bolts TIGHTER not looser.
The OP provided several clues to this...bolts definitely fly off when hitting something, and the bolts are not broken or damaged!
For giggles I would try left hand thread bolts, although one research about bush hog bolts the fellow said he uses a 10 ft. cheater bar and two extra helpers!

TerryR · Aug 20, 2019

How can the bolt be turning? The OP posted a link at the top of the thread to the bolt he uses, which has a key to keep it from turning. He also said there was a notch in the hole to fit that key. So if the bolt can't turn, and the blade swings free on the bolt, what makes the nut back off? It can't be the movement of the blade because the bolt can't turn in the hole.

MechanicalGuy · Aug 20, 2019

TerryR said:
How can the bolt be turning? The OP posted a link at the top of the thread to the bolt he uses, which has a key to keep it from turning. He also said there was a notch in the hole to fit that key. So if the bolt can't turn, and the blade swings free on the bolt, what makes the nut back off? It can't be the movement of the blade because the bolt can't turn in the hole.

The bolt either turns in the blade, or turns in the hub when swinging and stopping. I think that's what may be the question to the op right now. I believe the bolt should be stationary to the blades, but I don't know that for a fact.

TerryR · Aug 20, 2019

The OP said in post #5 that the notch that holds the bolt is in the plate that's welded on stump jumper. So the blade swings on the bolt, which is fixed to its attachment point on the stump jumper. That's the way my Bush Hog rotary cutter worked too.

So the bolt is supposed to be fixed, and the nut is against another fixed plate. So neither should turn. But it seems the nut does. How?

1010 · Aug 20, 2019

TerryR said:
The OP said in post #5 that the notch that holds the bolt is in the plate that's welded on stump jumper. So the blade swings on the bolt, which is fixed to its attachment point on the stump jumper. That's the way my Bush Hog rotary cutter worked too.

So the bolt is supposed to be fixed, and the nut is against another fixed plate. So neither should turn. But it seems the nut does. How?

Unless he has the wrong bolt's that are to long and the nut is bottoming out on the threads and not the top of the blade holder. The bolt has to be stationary with a tab that fits a slot in the blade holder OR the bolts have cut sides that fit into the same cut sides in the blade holder.. This ain't rocket science..