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Bush Hog Snapping Shear Bolts


 
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ScottNC
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PostPosted: Fri Sep 21, 2018 5:52 am    Post subject: Bush Hog Snapping Shear Bolts Reply to specific post Reply with quote

Haven't sheared one in years so when it popped I wasn't surprised, figured it wore in two. Snapped another one an hour later. It broke just as the clutch was being let out after backing up. Only thing that's changed is the tractor, instead of the old 2N I'm using an 885 David Brown. Grass and weeds is all that was being cut, no rocks or stumps.

Could the increase in torque and maybe unintentionally repeatedly disengaging/reengaging the pto clutch be the issue. I frequently forget that the clutch pedal only needs to be depressed a small distance to disengage power to the wheels versus the Ford. Figuring it was me I cut the head lands being careful with the clutch pedal then set the hand throttle and did nothing but turn the steering wheel and raise and lower the bush hog. Shear bolt lasted until the job was done an hour later.

What do you think, do I need a softer touch or is there something I need to do different now that I am using a real tractor?
 
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DoubleO7
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PostPosted: Fri Sep 21, 2018 7:53 am    Post subject: Re: Bush Hog Snapping Shear Bolts Reply to specific post Reply with quote

Unless your "popping" the clutch to start the pto, I would think there is something downstream of the shear pin causing increased resistance.
Are the shear pin holes all still round and close to the original diameter?
Did the old pin look very worn before failure?
 
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old
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PostPosted: Fri Sep 21, 2018 9:12 am    Post subject: Re: Bush Hog Snapping Shear Bolts Reply to specific post Reply with quote

As said popping the clutch will cause that. Also spinning it up when the engine is at high RPM does not help either. Also what is the Brush hog rated at for HP. If your trying to run it on a tractor with too many HP that can cause odd problems
 
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Traditional Farmer
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PostPosted: Fri Sep 21, 2018 11:01 am    Post subject: Re: Bush Hog Snapping Shear Bolts Reply to specific post Reply with quote

If you hadn't sheared one in years the PTO shaft was probably rusted to the gearbox shaft but now the rust is gone.
 
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ScottNC
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PostPosted: Fri Sep 21, 2018 11:06 am    Post subject: Re: Bush Hog Snapping Shear Bolts Reply to specific post Reply with quote

CVPost-old wrote:
(quoted from post at 10:12:06 09/21/1Cool As said popping the clutch will cause that. Also spinning it up when the engine is at high RPM does not help either. Also what is the Brush hog rated at for HP. If your trying to run it on a tractor with too many HP that can cause odd problems



It was used on a 1910 Ford (37hp) for many years until the flywheel broke. I pulled it out of a tree line, repaired it and have used it for six years on a 2N. Can't remember the last time a shear bolt snapped. It operates freely.

The 885 has ten more horsepower, more torque, a two stage clutch and the 3-point works whether the clutch is in or out, two things I didn't have available on the 2N. The bolt seems stupid easy to break. The brush hog hasn't changed, just me on a new tractor. Guess I need to be much easier engaging the PTO clutch and be careful in how fast the spinning brush hog is lowered. Plus, I bet I'm disengaging the pto and reengaging it in a loaded environment over and over when all I meant to do was disengage the engine clutch.
 
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PostPosted: Fri Sep 21, 2018 11:57 am    Post subject: Re: Bush Hog Snapping Shear Bolts Reply to specific post Reply with quote

Well one thing for sure breaking the shear bolt is by far the least expensive$ thing you can break.
 
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Case Nutty 1660
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PostPosted: Fri Sep 21, 2018 12:10 pm    Post subject: Re: Bush Hog Snapping Shear Bolts Reply to specific post Reply with quote

Myself I think you answered your question well, the 885 does not think or hesitate to be able to shear it if you are letting the pto slow down say 100 rpms when you are stepping on the clutch too far,, when you let out and again engage the pto clutch I bet it is Quick enough to snap the shear bolt,, I have done it before myself,, you will get more used to the two-stage pedal and I am thinking your issue will go away,, if all else fails you can for a couple hundred add a slip clutch in the drive line,, like said I would sure not go with a heavy shear bolt grade
cnt
 
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wellmax99
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PostPosted: Sat Sep 22, 2018 4:53 am    Post subject: Re: Bush Hog Snapping Shear Bolts Reply to specific post Reply with quote

Some may not agree with my fix to this problem
I have a small hog 5 ft Howse brand light to med duty cutter,
Pulled by a TO35 Ferguson

I changed from #2 grade sheer bolts to #5 grade bolts they are a little harder, but I just could not get anything done with the grade #2 bolts
sheering when I got into some heavy grass,
Do not have that problem with the grade #5 bolts, plus you still have the stump jumper to provide protection if you hit something solid,
I once had a ford cutter, did a good job but did not have a stump jumper and the slip clutch had been drilled and bolted together

Was not smart enough at the time to reason how dumb that was using that cutter with the slip clutch bolted together,
 
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Texasmark1
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PostPosted: Sat Sep 22, 2018 5:28 am    Post subject: Re: Bush Hog Snapping Shear Bolts Reply to specific post Reply with quote

Grade 2, sized to just fit the shaft (?"?) Lock nut but installed with slop, not tightened down. Engage at idle rpm only. Eventually it will get beat up
enough to shear. That has worked for me over the years when I was running older hogs with slop in the mechanisms. On newer hogs I do the same
thing...why change when you have something that works for you?
 
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Russ from MN
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PostPosted: Sat Sep 22, 2018 11:02 am    Post subject: Re: Bush Hog Snapping Shear Bolts Reply to specific post Reply with quote

I had a friend that said he could shear a pin in his cutter just by advancing the throttle too quickly! I think it was an
Oliver with a Detroit diesel. Is that a possibility?
 
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ScottNC
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PostPosted: Sun Sep 23, 2018 8:12 am    Post subject: Re: Bush Hog Snapping Shear Bolts Reply to specific post Reply with quote

I should probably keep this to myself. File it under, "Can't Fix Stupid". In my last-light-of-day haste, I grabbed the first box marked "shear bolts". Couldn't find the first snapped bolt in the poor light. As the nut was screwed on I wondered what I had been thinking of, buying bolts that were to short for the nylock in the nut to engage.

Figured it out when taking the brush hog off yesterday and saw all the snapped bolts lying in a pile of grass under the gearbox input. They were easy to see, all shinny new 3/8" bolts in three pieces, except for one... the rusty one. It was 7/16". Embarassed

Still, it was good to read the feedback from experienced people, your thoughts and suggestions will shorten my learning curve, so thanks.
 
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underp2
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PostPosted: Tue Oct 02, 2018 10:26 am    Post subject: Re: Bush Hog Snapping Shear Bolts Reply to specific post Reply with quote


I found the 2 stage clutch (JD 2020) is a little easier on the shear bolts than the independent PTO of (JD 2550). I can feather the clutch & start it up "softly". The independent PTO is a little more "all or nothing".

Where do you get 7/16" shear bolts? They seem to be very uncommon. I ended up getting a box of 25 from McMaster Carr. No one else had grade 2. Only grade 5 or grade 8.
 
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Dave O'Brien
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PostPosted: Wed Oct 10, 2018 7:12 am    Post subject: Re: Bush Hog Snapping Shear Bolts Reply to specific post Reply with quote

I would NOT recommend using a higher grade bolt. Somewhere along the line a grade 5 wound up on my bush hog and I wound up with oblong bolt holes on the stump jumper and could not keep blades on. Also broke the pto extension on the tractor, twisted the drive shaft and finally broke a u-joint. So now I keep a half dozen or so Gr. 2's in the tool box.
 
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underp2
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PostPosted: Wed Oct 10, 2018 7:24 pm    Post subject: Re: Bush Hog Snapping Shear Bolts Reply to specific post Reply with quote

Dave O'Brien wrote:
(quoted from post at 08:12:12 10/10/1Cool I would NOT recommend using a higher grade bolt. Somewhere along the line a grade 5 wound up on my bush hog and I wound up with oblong bolt holes on the stump jumper and could not keep blades on. Also broke the pto extension on the tractor, twisted the drive shaft and finally broke a u-joint. So now I keep a half dozen or so Gr. 2's in the tool box.


Agreed. Someone put a 3/8 grade 5 in. While I was going slowly through a rough logging trail, a hidden stump stalled the tractor! I made sure to get another box of low strength bolts after that.

I can't figure out where all the bolts go. Box of 25. I labeled the box "grade 2 shear bolts for FMC sidewinder rotary cutter/ bush hog". I've only broken 1 bolt. There's 5 left in the box. Who broke the other 19? And will they order more? Inform me it is time to order more? Ask for more when the box is empty and the last bolt breaks? Or just leave an empty box? Maybe put a grade 5 in there?
 
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ScottNC
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PostPosted: Fri Oct 12, 2018 6:24 am    Post subject: Re: Bush Hog Snapping Shear Bolts Reply to specific post Reply with quote

underp2 wrote:
(quoted from post at 11:26:11 10/02/1Cool
Where do you get 7/16" shear bolts? They seem to be very uncommon. I ended up getting a box of 25 from McMaster Carr. No one else had grade 2. Only grade 5 or grade 8.


I don't remember. A guess would be Tractor Supply but it has been five or six years ago and I can't even remember what I had for lunch yesterday.

There is no grade marking on the head, it's flat and smooth. Another guess is the now closed New Holland dealer. I was in there quite a bit while rebuilding a NH 450 sickle bar mower not long after acquiring this brush hog.
 
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