Shear Bolt Broke On New Deck. PTO Shaft & Gear Box Holes Don't Align.

TractorGuy

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I am truly a tractor tenderfoot, but with some machinery experience. The bolt that sheared may not be a "Shear Bolt," per se, but it is a bolt, and it did shear. I am working a slip clutch issue on a different thread based on a quote from my Frontier RC2060 manual.
My Frontier RC2060 manual has this quote:
"Slip Clutch Operational Check"
"After the implement has been stored for thirty days or more, perform the following operational check."

It goes on to describe how to loosen the bolts on the slip clutch and then to operate the PTO to make sure that the slip clutch . . . slips to protect the rest of the drive train. In my case, it does not slip (it sat for a long time prior to my ownership) and I'm in the process of figuring out how to get it free. The best advice I've gotten on this forum to free it is that while the bolts on the slip clutch are loosened, to engage the PTO back into heavy grass that would presumably cause the clutch to slip, then adjust the bolts as described in my manual and go about my mowing business.

Questions: Is it possible, that you engaged the PTO while at full-rated engine RPM, rather than engaging it at idle and then ramping up the RPM to full speed? I have heard anecdotally that such can shear bolts.

Why didn't your new mower come with a manual?

There are quite a few minor maintenance issues associated with tractoring, and you may want to consider getting familiar with them to save many trailer trips to the dealer.
In your case you should do as I had to. Remove the mower from the tractor. Remove All the clutch bolts. Tap the components apart with a hammer. Clean, reassemble, and adjust.

I check mine by loosening the bolts and turning the driveshaft piece with a 3ft screwdriver while locking the gearbox side so it can't turn. I tighten my nuts 1turn after contact and paint a line across the two halves. This serves as and indicator of if it slips when I've hit something.
 

DutchUncle

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I have a similar problem with a John Deere rotary mower. Mine's used and the the output shaft's hole is slightly oblong from wear. I shear bolts all the time. When the bolt is installed and snugged up I can rock it back and forth. IMO that is the OP's problem, If he bought it new, JD should fix it. A shear bolt is designed to be one with the shaft almost as it were all one shaft. The shear bolt is engineered to to have a lower tensile strength than the PTO and output shaft, so it should be the first to break, saving the gearbox and your tractor. No way it should shear mowing grass, maybe if you are going too fast and the grass is really tall, and thick. And as the prior poster mentioned always engage your PTO at idle.
 

sixdogs

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An aligning rod might take care of it. Otherwise, have you tried working a Philips screw driver with a shaft slightly smaller than the bolt into to hole to see if you can align them that way?
This is what I use to line up things that don't want to line up. `Makes lots of issues easier.
 

Midniteoyl

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Love when threads start to degrade due to people coming in after the problem has been figured and either not reading the whole thing to know that, or arguing against the solution and calling everyone else wrong.

The dude has a slip clutch. The OP *already* verified this, though he did not realize it at the time.

The bolt was not a 'shear bolt' per say, but held the slip clutch *and* acted as a 2nd line of defense in case of slip clutch failure. It is Gr.8 as per the manual and dealer.

The holes are *not* drilled at an angle, the PTO is simply not on far enough to align the holes.

OP has it all figured out now. How he will deal with it is up to him and what works best for him.
 
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Railroadman1

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the yoke & gear shaft are miss aligned take a screw driver, punch, or slide pto shaft to tractor or away to line hole replace bolt
 

mattoxb

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Be sure to engage the PTO at the lowest engine RPM possible. The impact load/ shear stress on that bolt when starting from a dead stop at too high RPM's can be much higher than from blade contact with a solid object at operating speed. I have an LX5 that likes to eat the same bolt if not careful when engaging the PTO. The slip clutch operates within spec. and I am using the specified "shear bolt" as so named in the operator's manual. Ease the PTO clutch in, do not engage all at once. I'm sure everyone knows this. Just trying to be helpful if there is someone who it might help.

Forgot to add one time the bolt had sheared just below the nut so the main part of the bolt stayed in for a while falling out some time later. So I believe it snapped when I engaged the PTO as I had not hit anything while operating the bush hog.
 

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pacerron

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Frontier used to be made by Woods maybe still is after Woods was taken on by an international company.
I've used a Woods RM 990 ( 7-1/2 foot) that I purchased new in 1988 for thousands of hours. I've replaced the shear pin several times ( grade 2, I don't have a slip clutch)
I suspect your grade 8 bolt has been broken awhile before the shaft totally stopped spinning. Do to the slope of the driveshaft from the tractor PTO to the mower gearbox the partially broken bolts sometimes get hung up and the shaft continues to rotate the gearbox shaft enough that it keeps cutting grass so you don't notice it. The drive shaft collar that goes on the gearbox shaft
gets some slop worn in it which elongates the hole through the shaft a bit. You just have to clean up the holes and align everything using a long tapered drift.
With the small number of hours you have on the mower something doesn't smell right. Are you sure the driveshaft you have on your mower is the correct length for your 3 point lift arms? If it is too long you could do serious damage to the tractor PTO. If it is too short the shaft won't have enough interlock.
 

the old grind

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When the implement's clutch is freed up IMO the '8' bolt should hold up. Glad it gave way vs worse happening.

I too wondered about PTO shaft length possibly causing undue axial stress, say when fully raised. (I use top hole for top link with cutters, tillers.)

btw, I never tighten 'true' shear bolts to their component more than finger tight then use jam nuts to hold them in place. Maybe more work than a clutch when afield esp w/o spares but they can sit longer w/o service. My tiller and flail sit outside all year. (wheeled pallets await, but lacking floor-space in barn) I'm glad only the KK tiller has a slip-clutch esp 'cuz I don't use it every year. It's always what works for each.
 

pacerron

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When the implement's clutch is freed up IMO the '8' bolt should hold up. Glad it gave way vs worse happening.

I too wondered about PTO shaft length possibly causing undue axial stress, say when fully raised. (I use top hole for top link with cutters, tillers.)

btw, I never tighten 'true' shear bolts to their component more than finger tight then use jam nuts to hold them in place. Maybe more work than a clutch when afield esp w/o spares but they can sit longer w/o service. My tiller and flail sit outside all year. (wheeled pallets await, but lacking floor-space in barn) I'm glad only the KK tiller has a slip-clutch esp 'cuz I don't use it every year. It's always what works for each.
 

pacerron

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I use Nyloc nuts rather than jamming 2 nuts. They are usually laying on the mower after breaking off and can be used again.
 
 
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