Constantly breaking shear bolts on my cutter....help?

[Ritothebull]

A grade 5 bolt from China is probably equal to a grade 2 USA made bolt if you're lucky. :laughing:

 

[darmstrong2319]

I have been using grade 5 for years and it always seems to shear when it should. I could not get anything done with grade 2, every time i hit a small clump of grass it would shear so I finally changed it to grade 5 and if I hit something it breaks like it should.

 

[sweettractors]

I have a 6 ft Land Pride Rotary cutter for my 45 hp LS
I turn the PTO speed down as slow as possible but I still shear a bolt on startup? What is the deal? Should I have it lowered to come in contact with some brush to slow the blades ramping up? I was told to have it raised when starting. I don't think I ever used it without shearing at least 1. I cringe every time I turn it on.

Suggestions??

Thanks

Make sure the blades are sharp to reduce stress on the driveline. Try increasing mowing rpm and slowing ground speed. Ken Sweet

 

[Coyote machine]

To the OP, What's the answer to something bent or bound up under the deck surface? If you have a problem and don't solve it, even by going to a stronger grade bolt, eventually you'll break your PTO stub/gears in the rear end- then you'll wish you'd found out what the actual problem is/was.:confused3:

 

[Fallon]

A grade 5 bolt from China is probably equal to a grade 2 USA made bolt if you're lucky. :laughing:

Believe it or not, they are pretty accurate. Home Depot Bolt vs. USA Made | Offshore Suprise! - YouTube

Personally I always read the manual & follow what it specifies. There are a number of combinations that will work. But unless you read the manual you wont know what the engineers specified for that particular implementation. Just because grade 5 are specified commonly doesnt mean the engineer that designed your machine didnt specify ungraded or grade 8 for some reason.

 

[DK35vince]

To the OP, What's the answer to something bent or bound up under the deck surface? If you have a problem and don't solve it, even by going to a stronger grade bolt, eventually you'll break your PTO stub/gears in the rear end- then you'll wish you'd found out what the actual problem is/was.:confused3:

I had the same problem breaking shear bolts on startup with my 6' brush cutter. Solved it with a slip clutch on the brush mower.
The problem was not the mower. The problem was the harsh startup with the electric/hydraulic PTO (even at idle).

 

[Trophyduck]

To the OP, What's the answer to something bent or bound up under the deck surface? If you have a problem and don't solve it, even by going to a stronger grade bolt, eventually you'll break your PTO stub/gears in the rear end- then you'll wish you'd found out what the actual problem is/was.:confused3:

Everything seem to be fine. I can rotate by hand, blades are free. Once it's mowing I'm fine......usually. I got to thinking, I hit a clump of dirt one time and it broke the bolt too. I didn't think that was right since it's supposed to handle a 2" sapling...
Also when running, it's smooth, no vibration or anything like that. I would think if something was bent, it would always shake

 

[DMW]

What is the size of the shear bolt? Have all the bolts that have been shearing from the same batch? Some chinese 3/8" Gr2 bolts can be sheared with hand tools quite easily, they are not all equal. I scrapped a lot of bolts because of this problem.

 

[compact]

It may be normal for your setup, I would use the recvomended bolt.

My RC2072 with slip clutch calls for a grade 8 bolt which regularly shears after about 20 hours use. I engage at 600 rpm etc. But the abrupt electric PTO clutch and rocks seem to batter it enough to fail. The clutch is set loose and even then... I think its the free play in the coupler that gives things a running start before the bolt binds up abruptly.

 

[Trophyduck]

What is the size of the shear bolt? Have all the bolts that have been shearing from the same batch? Some chinese 3/8" Gr2 bolts can be sheared with hand tools quite easily, they are not all equal. I scrapped a lot of bolts because of this problem.

I got the first batch at TSC....My Father-in-law picked some up at another Hardware store...Those do seem to last longer but probably my imagination.

 

[wagne223]

I have a 6 ft Land Pride Rotary cutter for my 45 hp LS
I turn the PTO speed down as slow as possible but I still shear a bolt on startup? What is the deal? Should I have it lowered to come in contact with some brush to slow the blades ramping up? I was told to have it raised when starting. I don't think I ever used it without shearing at least 1. I cringe every time I turn it on.

Suggestions??

Thanks

Some years ago I was in a similar situation although with a smaller tractor and cutter.
20 something HP B series and a 48 inches cutter I bought used.

It was a live PTO so I could engage it easy so the pins would not break starting the mower.
They would break while mowing no matter how light or heavy the grass.

A pin would not last more then an hour, and if I got into anything thick it would break immediately. Never even noticed the load on the tractor.

I tried every type of bolt known except grade 8 with no change. It was very frustrating as I would go through 5 to 8 pins in a day of cutting.

I had read a thread on here about it and one comment was if the holes on the PTO shaft and the gearbox shaft are elongated causing play, meaning worn out, the pin does not have a chance.

The holes on mine were worn out. On that setup, the shear bolt was 3/8".

What ultimately solved my problem was drilling out the PTO shaft and the gearbox shaft to accomidate a 1/2" bolt.
Note, I drilled it so the bolt had to be tapped into place. No freeplay or movement. And i used grade 5 bolt.

Used it for 3 more years like that with no issues. Then sold it to buy my current L2501. My current cutter has a slip clutch.

I'm not recommending you do what I did as I dont know if I caused any additional wear on the tractor PTO. But it solved my issue and I kept my sanity.

Because of that experience I will only own slip clutch shafts from now on. I dont mind staying on top of them and I like being able to set the slip point.
That is just me though.....a lot of people dont like to mess with the slip clutch as they do require maintenance.

 

[sdef]

I used to have problems shearing bolts on my Fred Caine subsoiler in my heavy, dense, root infested, rocky soil. Typically they would shear almost immediately no matter my operational methodology. I tried various bolt types and ended up going to a higher strength bolt, and I believe with more threads per inch. In this case, the tool is simply some thick pieces of metal that most likely would not get damaged by my using a shear bolt with more strength with my 6000 pound tractor.

Someone also mention elongated holes causing shock loads and I have seen that and fixed by drilling out the holes in a PHD with the auger shaft in place and adding next size larger bolts.

I also had a flail mower that would break shear bolts too easily, in my opinion, and upgraded the shear bolt by one grade and it still runs great for a farmer who now owns it. YMMV. I also had a slip clutch to add to it but ended up not being necessary.

This type of chart helped me to incrementally step up shear bolt changes without damaging anything, up to the bolt the tool actually worked with in my circumstances.
Bolt strengths

In the end the slip clutch may be the safest route to go.

 

[Birdhunter1]

I will have to agree that a grade 5 China bolt is near equal to a grade 5 US bolt. I experienced the same issue with my Landpride bushhog on a 50 hp tractor, I woudl go through a few in a n 8 hour span easily, I determined it to be the shear bolt holes in the yoke that were out of round and the amount of wobble the yoke had on the gearbox input shaft. I finally got a better idea and installed a clutch with a grade 8 bolt and I've not had a problem since.
Except a blade that broke and went through the side of the deck a few weeks ago, that was kind of a problem.

 

[SplitHoof]

First time using the bush hog with my TYM. Slow the idle to minimum, and try to get the cutter spinning by turning the switch on/off. Gave it up. Gonna order a slip clutch. Making me miss the clutched pto on the Ford 3000. Pretty frustrating afternoon.

 

[ruffdog]

If a 3/8" bolt (.375") is a bit loose, maybe go up to a 10mm (.394")? My Behlen 72" rotary cutter had a 1/2" bolt and I never sheared it. The tractor had a regular clutch so I could ease it started.

 

[SplitHoof]

If a 3/8" bolt (.375") is a bit loose, maybe go up to a 10mm (.394")? My Behlen 72" rotary cutter had a 1/2" bolt and I never sheared it. The tractor had a regular clutch so I could ease it started.

Mine are grade 2 @ 1/2” - never had issues with my old Ford.

 

[Texasmark]

On older implements with visible wear I used to shear bolts frequently till I did this:

Went to Grade 2 and used a lock nut with slack in the bolt-nut so it wasn't jammed up tight against the casting. Other thing using Grade 2 is when you did whack something solid and it did shear, you could find the broken part in the gearbox shaft because it smears when it breaks. Never could do that with 5s or 8s.

 

[Jack Yuan]

I have a 6 ft Land Pride Rotary cutter for my 45 hp LS
I turn the PTO speed down as slow as possible but I still shear a bolt on startup? What is the deal? Should I have it lowered to come in contact with some brush to slow the blades ramping up? I was told to have it raised when starting. I don't think I ever used it without shearing at least 1. I cringe every time I turn it on.

Suggestions??

Thanks

You can change to use slip clutch, easy to replace.

 

[Gary Fowler]

I have a 6 ft Land Pride Rotary cutter for my 45 hp LS
I turn the PTO speed down as slow as possible but I still shear a bolt on startup? What is the deal? Should I have it lowered to come in contact with some brush to slow the blades ramping up? I was told to have it raised when starting. I don't think I ever used it without shearing at least 1. I cringe every time I turn it on.

Suggestions??

Thanks

Brother in law has a 6 foot bushhog that did the same thing. Even if you got it started without snapping the shear bolt, it would shear just cutting grass. It had a 3/8" bolt for a shear and it didn't make any difference what grade of bolt use, it still sheared too easily. Finally I drilled out the bolt hole to 7/16" so he could use a larger shear pin. It still shears one now and then, but much less frequently.

 

[SplitHoof]

Talked to the dealer and found out the pto is on the same circuit as the power steering on my TYM and suggested I turn the wheels at idle to relieve some pressure and then engage the pto. Seems to help. I did go ahead and install a slip clutch as well.