shear bolt on brush hog?

[rk246]

Okay so I was at the dealer the other day and he had just delivered my new 60" brush hog, He was explaining everything to me and told me I should get a bunch of extra shear bolts for the pto shaft? He said that is designed to keep the gear box from being wrecked if I hit something substantial? So now my questions:
1. Does this shear bolt do a pretty good job of protecting the unit if say I hit a stump or rock?

2. The salesman and a parts guy were arguing over the grade of bolt, if it was grade 2 or 5? Anyone with some good knowledge on this want to tell me the difference? I am assuming that one is stronger than the other? by how much? Which should be on the unit? the salesman was telling grade 2 and the parts guy says grade 5?

Thanks,

Ryan

 

[sodamo]

I haven't experienced it yet on my brush hog, but hit a rock with the PHD and busted one today.

Don't know about the grading, I just bought same size (5/16) at the local hardware store.

David

 

[slowrev]

I just buy the unmarked cheapo bolts at TSC, grade 2 I think ? I believe it is safer to try the softer ones first and see how they do. Too hard of a bolt and you might break your gearbox, either on the hog or in your tranny /forums/images/graemlins/frown.gif
I would also recommend a slip clutch on your hog.

Ben

 

[Cottonhawk]

I broke one last summer. It's the bolt connecting PTO to the gears in the gear box. It broke into three pieces and the gear box was fine. The bolt is fairly easy to replace.

 

[BB_TX]

1. Yes, it does a good job of protecting the gear box and the tractor PTO drive.
2. What does you manual state? Most, I think, use a grade 2 (soft) bolt. That is what I use and, yes, I keep several on hand. I will shear one every 10-20 or so hours of mowing.
Here's <font color="blue"> some info </font> on bolts.

 

[Ranch_Hand_Supp]

Grade 2 bolt with a lock nut or double nut's to keep it from working loose works well.

Ronald
Ranch Hand Supply

 

[450EXC]

I tried a grade 5 on my snowblower. It didnt break anything but the bolt mangeled, not a clean shear. 4 hours later I had it apart and put a grade 2 in.

 

[Highbeam]

Grade two. Note the marking on the head of the current bolt. The number of marks dictate the strength. The owner's manual should also specify.

I paid the extra 100$ for a slip clutch so I don't have to stop mowing to replace a busted shear bolt. My luck, the new one would fall out of my pocket into the grass or I would not have one when needed. You can always add a slip clutch later if you find that the shear bolt system stinks.

You can hit stumps and rocks. The brush hog is a magnificent machine and quite a brute. Be careful though as rocks can be shot out the rear of the hog. I have shot rocks the size of baby heads for hundreds of feet. Seriously, that could kill someone.

Go slow at first and prepare to get that holy smokes feeling.

 

[3RRL]

</font><font color="blue" class="small">( Go slow at first and prepare to get that holy smokes feeling.)</font>
That's a great description! /forums/images/graemlins/smile.gif

 

[SWB]

I have had a variety of rotary mowers over a 30 year period. All with shear bolts and none with a slip clutch. They don't break often but I have broken a lot of them over a 30 year period. Hit a lot of stumps and rocks. Never damaged a gear box yet.

 

[RalphVa]

I hadn't hit much but had done a lot of grass cutting before breaking a bolt when I went off trail a little bit and hit 3 or 4 1-2" each pieces of branch all clumped together.

The bolt on an LX4 is located just in front of the gear box. I figured it'd shear off both ends of the bolt and leave the shaft in the hole, and I'd have to poke it out. Nope. It just sheared one end, and the bolt flew out.

I bought 3 more at the dealer. They actually look like about a grade 8 bolt. Don't remember what the parts lady said they were. Figured buying them at the dealer is safe, maybe a bit more expensive than at Lowes or some such place.

I've hit some pretty good rocks and stuff with this second bolt and haven't broken it yet.

Ralph

 

[HGM]

Guys,
Pardon my ignorance here, the only advice I could give is the lesser grade the better. I would rather break a bolt than a gear. But the thing that concerns me is that some of you guys break an awfull lot of these shear bolts /forums/images/graemlins/confused.gif.

Not that you're doing something wrong, I really dont know because I only have 150-200hrs on a tractor and not all w/a cutter. The cutter I have and the others I've used have "stump jumpers" on them to help avoid breaking the gearbox shaft. I've always taken it slow when I didnt know what was under the brush I cut and havent broken a bolt yet(wait till next time /forums/images/graemlins/grin.gif) My question is, is it really that common or do you guys mow more agressively than I do?

I might get a couple of bolts to keep in my tool box after reading this. I also plan on getting a slip-clutch for the tiller, will it piggie back the one way I have on my Yanmar?
/forums/images/graemlins/grin.gif
Greg

 

[yugo]

Ryan, Fuel for thought - I highly agree with the grade 2 bolts. What wasn't brought up in this forum is most moderate priced brush hogs, and mower decks have a 45 hp rated gear box with possibly a 5 grade bolt for the 45 hp gear box. BUT, how big is the tractor PTO gears? Are we talking about a 25-40 hp tractor? So, with that question, you may want to use a grade 2 bolt. One other little hint - when the brush hog is new - when you do preventive maintenance - remove the PTO shaft where the bolt is, and put a thin layer of grease, then reinstall. If that PTO coupling rusted to the gear box shaft it may take a 100 hp to free up the rust, and shear the bolt. The lighter weight bolt will save your equipment from damage. Good luck - Yugo

 

[MikeD74T]

I've had a 60" bushog for about 8 years. The dealer gave me a grade 5 bolt & suggested I replace the installed grade 2 with it. The grade 5 lasted for 7 years. I was using an 800 Ford diesel, about 35 hp. This year I broke a bunch of grade 5 bolts. Got a new Kioti DK45S. It wasn't so much the extra hp as it was the electric pto. My old practice was to set engine speed and let out the clutch ( not live pto). If you set the speed and instantly apply 45 hp the bolt doesn't stand a chance. I broke 3 in 10'. Never said I was a fast learner! Got much better when I engaged the pto at lower speed then increased rpms. Bought a slip clutch for next year as I have the option of auto disengaging the pto when the 3pt hitch lifts. If I use that without the slip cllutch the bolt breaks when I lower and auto re-engage.

 

[BillyP]

The only thing I have that uses a shear bolt is a litter machine (kind of like a tiller). It came with and calls for 8.8 grade shear bolts. 8.8 is metric which would be a grade 5 in SAE.

 

[Soundguy]

</font><font color="blue" class="small">( I was using an 800 Ford diesel, about 35 hp. )</font>

Maybee 48-50 hp would be a bit closer to the 172ci 8XX diesel hp...

35 hp is closer to the gas 134ci red tiger engine the NAA/6XX series used...

Soundguy

 

[chili]

I went to TSC store and they had a package of 5 bolts for a brush hog and it noted Grade 2 on the package and sold for around 6 to 7 dollars. I went to their bolts bin and bought the same grade 2 bolts of which they sell by wieght and paid under 2 dollars.

 

[rk246]

Thank you everyone for all the information, I really appreciate it, Grade 2 sounds like the way to go. I did some cutting the other day, hitting a lot of stuff, (I am still clearing my land) and was lucky I guess, everything worked well.

As for the slip clutch, can someone explain this further?

Thanks again,

Ryan

 

[Highbeam]

Ever driven a stick shift auto? The slip clutch works like a car clutch that normally is a rigid connection but allows the connection to slip if a big impact occurs. After the big impact, the slip clutch quits slipping and you can go about mowing. No stopping to change the shear bolt, no forgetting to buy extras, and no tools needed. Best 100$ I spent in a long time.