Rotary Cutter Brush Hog Blades COMING OFF

[Shaneard]

I think you need some left handed bolts. That way they tighten themselves instead of loosen themselves like they are doing now. I don't know, just a guess.

 

[Shaneard]

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.

According to this page you couldn't be more wrong.
Are Grade 8 bolts more brittle than Grade 5? (8.8 vs 1.9 Metric) | Helping you work smarter not harder

 

[MechanicalGuy]

According to this page you couldn't be more wrong.
Are Grade 8 bolts more brittle than Grade 5? (8.8 vs 1.9 Metric) | Helping you work smarter not harder

That page doesn't refute the fact that grade 5 bolts are used in suspension, braking, towing, and have better elongation characteristics than grade 8.

 

[Shaneard]

That page doesn't refute the fact that grade 5 bolts are used in suspension, braking, towing, and have better elongation characteristics than grade 8.

Grade 5 bolts are used by manufactures where they can because it saves them a ton of money over time.

Do a test yourself, get a grade 5 bolt and a grade 8 bolt, clamp them in your vice and hammer them to a 90 degree angle. See which one breaks first, if either.

 

[Ford850]

Here's another link, to a bog regarding the myth about grade 5 being used for suspension etc. Killing the myth of the Grade 5 bolt. Industrial Chassis Inc.
And that page has a link to some great bolt science resources Information related to bolted joints

From some of that reading, the reason for the OPs bolts loosening could be from the mismatched bolt causing a sloppy fit on the blade http://www.boltscience.com/pages/Why_nuts_and_bolts_can_self-loosen.pdf
The solution is probably to get the correct OEM part.

 

[MechanicalGuy]

Grade 5 bolts are used by manufactures where they can because it saves them a ton of money over time.

Do a test yourself, get a grade 5 bolt and a grade 8 bolt, clamp them in your vice and hammer them to a 90 degree angle. See which one breaks first, if either.

No. That is not correct. Instead of being combative and argumentative, you might take a minute to learn something from the link that you posted yourself. Grade 5 is specified for brakes, towing, suspension, and other applications for the toughness of the material. The grade 8, as you can see in the graph you posted yourself, breaks suddenly, and without deformation. The grade 5 has a long yield curve. Now it's not only important to be able to read and understand that graph, but it's important to understand why manufacturers who are subject to liability lawsuits for the products that they make, would specify the grade 5. The grade 8 only retains it's superior strength if the bolt in question is torqued properly, for the life of the fastener. That is key to understand. Through the life of a fastener, use cycles, heat cycles and corrosion, bolts lose their torque. When this happens, they fail. Grade 8 fail in a catastrophic manner, whereas grade 5 provide warning. Your brake bracket will still be attached to your axle, or your trailer hitch will still be attached to your frame.

Go ahead. Look at these components and see if they are not put together with grade 5 bolts. I'm not just making this **** up. I have a degree in Mechanical Engineering and I actually read manuals when I install aftermarket brakes on my trailer, or my trailer hitch on my vehicles. Grade 5 are used for their ability to yield slowly and not catastrophically fail.

 

[MechanicalGuy]

In engineering, the area under the curve is known as the toughness. Here it can be seen that the grade 5 has it in spades over the grade 8

Sorry if that doesn't comport with a blog on the internet.

There are many tutorials but this one should suffice;

Strength, Resilience, Ductility, Brittleness, Toughness, Rigidity in materials - YouTube

 

[countrybumpkin]

You two need to start another thread, your way off topic to be helping the original poster now.

 

[countrybumpkin]

The bolts have a shoulder that bottom out on the blade carrier they don’t tighten up against the blade, the blade has no effect on the nut turning.

 

[radios1]

View attachment 617886

In engineering, the area under the curve is known as the toughness. Here it can be seen that the grade 5 has it in spades over the grade 8

Sorry if that doesn't comport with a blog on the internet.

There are many tutorials but this one should suffice;

Strength, Resilience, Ductility, Brittleness, Toughness, Rigidity in materials - YouTube

if they are heat treated to RC33-39, that makes them more tough. as a matter of fact, milling machine clamp sets are RC50, and never broke, they bent instead..