Everything you need to know about SHEAR BOLTS
- Thread starter KeithG
- Start date
keith
just saw this post, thanks for the info. i'm in NH also, and had the same problem on that storm. i've got a b2650hsdc with front blower. i've gone through 5 shear bolts this winter. on my old jd 2305, i went through 4 in 7 years, including last year with what, 8' of snow? now that i've seen this thread, i'm going to see if the shear bolts that i got for the tractor are the proper grade.
thanks
just saw this post, thanks for the info. i'm in NH also, and had the same problem on that storm. i've got a b2650hsdc with front blower. i've gone through 5 shear bolts this winter. on my old jd 2305, i went through 4 in 7 years, including last year with what, 8' of snow? now that i've seen this thread, i'm going to see if the shear bolts that i got for the tractor are the proper grade.
thanks
Good info, Thanks!
I lost a shear bolt on my rotary cutter. I think it was only because it had never been tightened from the mfg or possibly when assembled at the point of sale. (Farm and Fleet retail chain)
Needing a replacement bolt, I found myself at the same farm store looking at all the many bolts available. A helpful store employee came by and asked if I needed assistance and I explained my problem. He walked my down the aisle and showed me a blister pack of 5 from the same mfg as my cutter for $8. Exact replacements. I put 1 in power shaft, 1 in the toolbox on the tractor, and the rest on the pegboard over the workbench.
Haven't needed one since!
I am firmly convinced that HAVING 4 of them conveniently on hand, eliminates any future NEED for one.
I lost a shear bolt on my rotary cutter. I think it was only because it had never been tightened from the mfg or possibly when assembled at the point of sale. (Farm and Fleet retail chain)
Needing a replacement bolt, I found myself at the same farm store looking at all the many bolts available. A helpful store employee came by and asked if I needed assistance and I explained my problem. He walked my down the aisle and showed me a blister pack of 5 from the same mfg as my cutter for $8. Exact replacements. I put 1 in power shaft, 1 in the toolbox on the tractor, and the rest on the pegboard over the workbench.
Haven't needed one since!
I am firmly convinced that HAVING 4 of them conveniently on hand, eliminates any future NEED for one.
Not so sure about this. I buy grade 2 bolts about a dozen at the time from lowes. Keep several on the tractor for my rotary cutter and rarely go two consecutive weekends without having to replace one. But what was said about keeping the RPMs up is the key, they only bust when at a low RPMS and trying to speed back up.
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KeithG
Member
Equipment
2000 Kubota B2710, Woods BH75 backhoe, LandPride York Rake, B2783 Snow Blower
I was told by a tractor dealer (i.e. not Kubota) that SHEAR BOLTS are only grade 2 bolts, which is TOTALLY INCORRECT. As I stated in my original posts the most important thing is to find out what type of bolt should be used in your implement. In my case if I used a grade 2 bolt I would be giving up over 1,500 pounds of shear force which means I probably would not make it through one storm of heavy wet snow. This would be aggravating and a waste of time to put in new bolts so often. I am a believer in being conservative that is why I use a grade 8 THREADED bolt vs. a grade 8 SOLID bolt. That means I am still 1,300 pounds below the possible implement failure rating but there is no data sheet that states implement will fail at xxxx pounds of force. So I find out the specs. needed and go slightly less than that but I don't think I will ever use a grade 2 bolt unless the implement specifically says to... My 2 cents....
Mostly I was just presenting bolt data for everyone to make their own decisions to get the best/most use out of their tractors.
I was told by a tractor dealer (i.e. not Kubota) that SHEAR BOLTS are only grade 2 bolts, which is TOTALLY INCORRECT. As I stated in my original posts the most important thing is to find out what type of bolt should be used in your implement. In my case if I used a grade 2 bolt I would be giving up over 1,500 pounds of shear force which means I probably would not make it through one storm of heavy wet snow. This would be aggravating and a waste of time to put in new bolts so often. I am a believer in being conservative that is why I use a grade 8 THREADED bolt vs. a grade 8 SOLID bolt. That means I am still 1,300 pounds below the possible implement failure rating but there is no data sheet that states implement will fail at xxxx pounds of force. So I find out the specs. needed and go slightly less than that but I don't think I will ever use a grade 2 bolt unless the implement specifically says to... My 2 cents....
Mostly I was just presenting bolt data for everyone to make their own decisions to get the best/most use out of their tractors.
Keith, that was meant as a response to the other thread about buying a pack of 5 bolts and still having 4 on hand eliminates the need for them. It was meant as a joke... because I go through them frequently.
I do think your information is very valuable and accurate. I know that in my case on a PTO shaft, I will stick with grade 2 as I would rather replace bolts than a gearbox or an engine.
And for those of you that need info on metric grading, here's a link that may help. I broke one on my Land Pride rototiller gearbox input shaft, and had to look pretty hard to find some Class 8.8 bolts locally.
Not that it matters when used in shear, but the tensile strength can also be affected by weather or not the threads are wet or dry (lubed or not), especially the structural grade bolts. I guess my point is that if you over tighten the bolt, the shear strength will be decreased.
https://www.boltdepot.com/fastener-information/materials-and-grades/bolt-grade-chart.aspx
Thanks for all the helpful info, everyone.
Not that it matters when used in shear, but the tensile strength can also be affected by weather or not the threads are wet or dry (lubed or not), especially the structural grade bolts. I guess my point is that if you over tighten the bolt, the shear strength will be decreased.
https://www.boltdepot.com/fastener-information/materials-and-grades/bolt-grade-chart.aspx
Thanks for all the helpful info, everyone.
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I broke two in my shredder almost immediately when it was new. One was starting the PTO at too high an RPM (rookie mistake), and the second was hitting a snag of barbed wire that was buried in deep grass. I went to TSC and just bought the blister pack of 5 and haven't needed one since. So I guess that confirms Knightgangs theory.
Funny thing - about two weeks ago my wife was walking along the drive to our barn and found a sheer bolt (without washer or nut) laying on top of the gravel. It looked new. I have no idea where it came from. I am not missing any and haven't had anyone with equipment out for almost a year. Maybe I have a mystery mower sneaking in to do work for me.
Funny thing - about two weeks ago my wife was walking along the drive to our barn and found a sheer bolt (without washer or nut) laying on top of the gravel. It looked new. I have no idea where it came from. I am not missing any and haven't had anyone with equipment out for almost a year. Maybe I have a mystery mower sneaking in to do work for me.
Although there are specific application pins, bolts, and keys, that are made only for Shear purposes, many applications use standard bolts, pins, keys for Shear applications. If Kubota states a "Grade 8 shear bolt" they are talking about a standard bolt used in a shear type device. Therefore, it is perfectly acceptable to call it a shear bolt, even though the bolt manufacturer does not call it that. It is just semantics.
Also, depending on the diameter, the metal, and other variations, bolts under 1-1/4" in length, are fully threaded. From 1-1/4" to 6" you have an option for partial or full threads. Above 6" length, they only have partial threads.
If you are having problems with nuisance failures, you should try Mil Spec. bolts that meet much tighter standards and testing, as most imported bolts are of questionable quality. McMaster Carr online is the largest hardware company in the world and will have what you need for a reasonable price plus shipping.
Your calculations are impressive, but if the holes in the coupling are wallowed out, the inertia of the shaft can shear the bolts more easily.
My advice? Just spend the money and get a slip-clutch drive shaft, they are not that high.
Also, depending on the diameter, the metal, and other variations, bolts under 1-1/4" in length, are fully threaded. From 1-1/4" to 6" you have an option for partial or full threads. Above 6" length, they only have partial threads.
If you are having problems with nuisance failures, you should try Mil Spec. bolts that meet much tighter standards and testing, as most imported bolts are of questionable quality. McMaster Carr online is the largest hardware company in the world and will have what you need for a reasonable price plus shipping.
Your calculations are impressive, but if the holes in the coupling are wallowed out, the inertia of the shaft can shear the bolts more easily.
My advice? Just spend the money and get a slip-clutch drive shaft, they are not that high.
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ZZZRSC, the problem is if the slip clutch is not adjusted properly one is no better off then the sheer bolt.
I can't argue with that, my brother made a lot of money manufacturing and selling clutch adjustment tools for the old Gravely walk-behind tractors. It was basically an old style beam type torque wrench and an adapter to fit the end of the clutch. It can be a real problem on if you don't have the right tool, or the knowledge of how to set it.