Rotary cutter shear bolt

[9er]

What grade/strength shear bolt should I use on my rotary cutter. It's a 5 foot stump jumper and I have now sheared 2 in an hour. One I can understand...hit a hidden stump. The other one got my goat. I have seen my pa-n-law cut down scrub trees that I figured it couldn't and never miss a lick. The ones I bought are #2 grade. Any thought...and if any ideas, where can I order stronger ones on line. Thanks
Jeff / 9er

 

[smstonypoint]

This issue has been discussed in several threads. I remember one in particular from this summer: http://www.tractorbynet.com/forums/attachments/321990-farmline-5-dx-cutter-shear.html.

Post #5 in that thread:

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?

I bought a Bush Hog BH14 this summer and asked the dealer to throw in some spare shear bolts as part of the deal. The manual specifies #2s, but the dealer provided #5s, saying his parts department didn't even stock #2s.

Steve

 

[Sodo]

I think the optimal situation is to have a bolt that is just about to break whenever you get into some thick stuff. Consequently it's operating at its fatigue limit, thus it will probably fatigue, and break anyway, after a period of usage. It's an in-elegant system in some ways but elegant in other ways (low cost and ease of replacement). I would NOT use a Grade5, you are losing a "safety" that is necessary.

So what if you break a couple Grade2 bolts a year? It doesn't take long to fix and doesn't cost a lot, and is much cheaper than any other insurances you buy, or any "extended warranty".

If it's really happening too frequently, a small step stronger might be to simply use a longer Grade2 bolt, such that the shank (the un-threaded portion) fully crosses the coupling, and there's only a couple threads within the coupling.. You may need extra washers, or a 5/8" nut (as a spacer) to accomplish this.

I'm pretty sure the bolts at Home Depot (and other stores) that have the 3-character (ABCs) on them, and no other markings, are grade2. Here's a video telling about bolt grade markings.

Determining Bolt Grade and Head Markings - YouTube

 

[Rocky Hoffler]

I use grade 5 I/2 inch bolts that I buy a dozen at a time from bolt supply grade 2 just shear at anything

 

[boggen]

shear bolts protect your tractor for most likely very costly repair bill!!!

another solution is a slip clutch, most rotatory cutters come with a slip clutch, that is normally mounted between PTO shaft and gear box on rotatory cutter. BUT!! slip clutches do need to be maintained, and set correctly.
Tractor Attachments And Skid Steer Attachments For Any Tractor Or Skid Steer has some decent text and video in adjust and setting a slip clutch.

 

[Texasmark]

What grade/strength shear bolt should I use on my rotary cutter. It's a 5 foot stump jumper and I have now sheared 2 in an hour. One I can understand...hit a hidden stump. The other one got my goat. I have seen my pa-n-law cut down scrub trees that I figured it couldn't and never miss a lick. The ones I bought are #2 grade. Any thought...and if any ideas, where can I order stronger ones on line. Thanks
Jeff / 9er

My JD baler specifies a grade 8 bolt and says grade 8 will snap and not smear so that you can find the hole and are easier to drive out. I used the grade 2 bolts for years and always had that problem thinking grade 2 is softer which it is, but this is shear, not tension.

The other thing I found is that my bolts last indefinitely on my shredder if I use a lock nut and don't tighten them all the way down on the coupling...leave a little slack. Not sure as to the physics of that but it works for me. I run grade 5 on them (3 strike marks). Any hardware store carries grade 5.

Mark

 

[wrangler6831]

We bought a 6 ft BH a few years ago and it came (by mistake) from the factory with Grade 8. It ended up breaking the ear off the u-joint and bending the drive shaft. Took it back to the dealer who called the factory and they said the had some that were shipped that way accidentally and the warrantied the driveshaft. I def would not use anything above a grade 5 for a BH.

 

[Ford850]

I always use grade 2 that I buy in bulk at Rural King or TSC. Sometimes I do have 2 break within a week's time, but that is rare. Otherwise I replace a couple per year. I don't understand the "smear" comments. There is no space on my cutter to allow the bolt to smear. When they break, they pop clean and easy to remove.

 

[Soundguy]

check the implement manual. i like to use the lower end of what ever works.

ie. gr2 unless it's a special setup using a reduced diameter 5 or 8.. like a flange setup.

 

[newbury]

What grade/strength shear bolt should I use on my rotary cutter. It's a 5 foot stump jumper and I have now sheared 2 in an hour. One I can understand...hit a hidden stump. The other one got my goat. I have seen my pa-n-law cut down scrub trees that I figured it couldn't and never miss a lick. The ones I bought are #2 grade. Any thought...and if any ideas, where can I order stronger ones on line. Thanks
Jeff / 9er

Really? I didn't think a cutter would shear a bolt hitting a goat.

The other one got my goat.

As far as ordering :Agri Supply - Search
$2.49/lb plus shipping.

shear bolts protect your tractor for most likely very costly repair bill!!!

another solution is a slip clutch, most rotatory cutters come with a slip clutch, that is normally mounted between PTO shaft and gear box on rotatory cutter. BUT!! slip clutches do need to be maintained, and set correctly.
Tractor Attachments And Skid Steer Attachments For Any Tractor Or Skid Steer has some decent text and video in adjust and setting a slip clutch.

Slip clutches are nice and expensive.

most rotatory cutters come with a slip clutch,

Not where I shop. Looking at TSC and Agrisupply they don't mention it on the 5' ones I viewed. At everything attachments the Fred Cain line comes both ways. It's about $100 more for the slip clutch version.