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

[Trophyduck]

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

 

[TractorNH]

Are you using the correct grade bolt? Alternative is to replace the shear bolt with a grade 8 bolt and get a slip clutch instead.

 

[CobyRupert]

Yep, slip clutch may be the answer.

...or a tractor with a PTO lever (or 2 stage foot clutch) that you can ease the PTO clutch into engaging.

Lowering it into brush will just make the start-up "shock" worse. Having someway to have the mower spinning before you start the PTO would be less of a shock, although a bit impractical and probably dangerous.

Why did so many manufacturer's start making the PTO activated with a push/pull, 2 position only (binary) pushbutton that slams the PTO on?

My lawn mower is like this. Hate it.

 

[Ford850]

You'll get all sorts of suggestions since tractors and cutters vary a great deal on how thy engage. I have to ease my PTO lever otherwise I pop shear pins too. I lower RPM, then ease the PTO lever into position and it works fine.

 

[oosik]

You turn the PTO speed down as slow as possible - do you mean the tractor is idling? Is you PTO engagement an electro-mechanical engagement system? On my tractor I can "slip and feather" engagement with the PTO lever - just like the clutch on a manual transmission car. Electro-mechanical can be a fairly harsh, jarring, abrupt engagement system. These type system should be able to be adjusted by the dealer.

I don't say you necessarily need to use the OEM shear bolts but if you do not - whatever you are using should be the same grade.

Another answer would be as TractorNH indicates. Install a slip clutch, properly adjust it and instal a grade 8 shear bolt.

However - be advised - many PTO implements have Grade 8 OEM shear bolts. My Wallenstein BX62S OEM shear bolt is grade 8.

 

[smstonypoint]

The OP hasn't specified the grade of the shear bolts he is using. According to Why did the shear bolt break on my driveline? | Land Pride, Land Pride recommends grade 2.

I think I am correct in remembering a TBN discussion dealing with a similar problem on a Bush Hog rotary cutter. Someone said that he had called Bush Hog to discuss his problem. The Bush Hog rep told him to switch to a grade 5 bolt rather than the grade 2 bolt specified in the owner's manual. When I bought my BH14, the salesman provided me with grade 5 bolts as spares, saying that the dealership didn't even carry grade 2 bolts.:confused3:

Steve

 

[Katahdin]

The shear bolts on my 6-foot King Cutter are 1/2" diameter, grade2, that I buy at Tractor Supply. I've never broke one on startup, I set the engine rpm at 800 before activating the PTO switch. I don't go into the bush until its spinning at full PTO rpm.

 

[mykleh]

only other offer would be do you have the deck to high that the pto shaft angle is crazy? having the pto shaft at most normal angle would probably help as well..

 

[Rock knocker]

The OP hasn't specified the grade of the shear bolts he is using. According to Why did the shear bolt break on my driveline? | Land Pride, Land Pride recommends grade 2.

I think I am correct in remembering a TBN discussion dealing with a similar problem on a Bush Hog rotary cutter. Someone said that he had called Bush Hog to discuss his problem. The Bush Hog rep told him to switch to a grade 5 bolt rather than the grade 2 bolt specified in the owner's manual. When I bought my BH14, the salesman provided me with grade 5 bolts as spares, saying that the dealership didn't even carry grade 2 bolts.

Seems really weird that a rep would recommend Grade 5 bolts when the documents state that Grade 2 is to be used. Unless I had written instructions to ignore the manual and use Grade 5, I'd stick with what the manufacturer has written down.

Slip clutch is the way to go

 

[smstonypoint]

The OP hasn't specified the grade of the shear bolts he is using. According to Why did the shear bolt break on my driveline? | Land Pride, Land Pride recommends grade 2.

I think I am correct in remembering a TBN discussion dealing with a similar problem on a Bush Hog rotary cutter. Someone said that he had called Bush Hog to discuss his problem. The Bush Hog rep told him to switch to a grade 5 bolt rather than the grade 2 bolt specified in the owner's manual. When I bought my BH14, the salesman provided me with grade 5 bolts as spares, saying that the dealership didn't even carry grade 2 bolts.:confused3:

Steve

Seems really weird that a rep would recommend Grade 5 bolts when the documents state that Grade 2 is to be used. Unless I had written instructions to ignore the manual and use Grade 5, I'd stick with what the manufacturer has written down.

Slip clutch is the way to go

Here's the post I mentioned. I was mistaken about the poster having a problem (one of my senior moments)-- he was just relaying the info he received from the factory rep.

Recently bought a new Bushhog RD5 5ft cutter. Asked the dealer what shear bolt grade to use and to supply a few spares. He insisted that it used (and he supplied) grade 5. After reviewing the manual, it calls for grade 2. Called Bushhog tech/service. They actually recommended grade 5 on the theory that they would snap cleanly rather than bend and smear. I was astonished. Now not really sure which to use. Maybe it really doesn't make all that much difference?

- Jay

My dealer experience was the same as Jay's.:confused3:


Steve

 

[Rock knocker]

Weird. I'd want to do that via a confirming e-mail

 

[smstonypoint]

Weird. I'd want to do that via a confirming e-mail

I've had by Bush Hog BH14 for nearly four years and have yet to break a shear bolt. I don't know how Bush Hog rotary cutters are shipped. If the PTO shaft is attached to the gearbox at the factory, I suppose I have a grade 2 bolt:confused3:


Steve

 

[Trophyduck]

You turn the PTO speed down as slow as possible - do you mean the tractor is idling? Is you PTO engagement an electro-mechanical engagement system? On my tractor I can "slip and feather" engagement with the PTO lever - just like the clutch on a manual transmission car. Electro-mechanical can be a fairly harsh, jarring, abrupt engagement system. These type system should be able to be adjusted by the dealer.

I don't say you necessarily need to use the OEM shear bolts but if you do not - whatever you are using should be the same grade.

Another answer would be as TractorNH indicates. Install a slip clutch, properly adjust it and instal a grade 8 shear bolt.

However - be advised - many PTO implements have Grade 8 OEM shear bolts. My Wallenstein BX62S OEM shear bolt is grade 8.

I'm using Grade 2 bolts as recommended and it is Electro-mechanical.
I have the Tractor at idle speed, then pucker up when I engage the PTO. Last time I used it, I had it off the ground, but not too high and it was shockingly quiet and didn't break for several starts and stops. Then I started it again and bang, broke. Sometimes when it starts up it shakes the whole tractor. Dealer said it will not be as bad the more I use it and to keep the pivot point lubed and that initially, because things are so new/tight breaking a few pins is "not unusual"....

 

[DMW]

Check the oil level and condition of the gears of the brush cutter if possible. Grease up the pto shaft, universal joints and the inside of the shaft. As others have said, engage with the least amount of angle on the pto shaft. Something is binding somewhere if the correct grade shear bolt is being used.

 

[Coyote machine]

Any bent/damaged blades or wire bound around anything on the underside of your rig? Can you turn the driveshaft by hand with the PTO shaft disconnected from the tractor PTO stub?

 

[oosik]

I'm sorry but "breaking a few pins is QUITE unusual". Something is not right. The pins simply should not shear on startup. I would press the issue with the dealer.

 

[LouNY]

Without more info it's hard to say,
what type of pto engagement do you have a mechanical lever?
or an electrical switch?
what do you have for a transmission? shuttle ? or hydro?
If its mechanical engaging it slowly and smoothly at the lowest rpm is your answer.
If its electrically activated the first thing is again have the engine rpm at the lowest possible.
If electrical do you have a linked / independent switch? if so try the linked position then
with your foot clutch disengaged, pushed down, turn on the pto switch, it may not run, gently release your foot clutch pedal
and the pto may engage with the main clutch, allowing you to ease it in.

 

[Ritothebull]

I had an old bush hog that came with a tractor I bought and that thing broke a bunch of shear bolts. Everything seemed fine with it mechanically, I tried different grades of bolts and feathered it into gear as gently as I could, sometimes I could cut for hours and other times it would shear off in 5 minutes. I finally sold that thing and bought another mower and now I haven't sheared a bolt in years and I'm using the same tractor so maybe that thing was just jinxed.

 

[WranglerX]

Everything I have seen or read state grade 2 shear bolts...

Dale

 

[DK35vince]

My King Kutter brush hog would sheer bolts at startup also. (PTO turned on by a switch at idle)
I added a slip clutch and haven't had a problem since.