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  1. #1

    Join Date
    Jul 2001
    Posts
    1,807
    Location
    Sharpsburg, Md
    Tractor
    John Deere 4100 HST

    Default PTO shear pin advice.

    Want to have a supply of shear pins for my Woods rotary cutter. The manual recommends a Grade 2 NC 1/2"X3" shear bolt with a lock nut.

    Went to my local Quality Farm and Home Supply store which was out of Grade 2 shear bolts. Asked one of the "associates" if they had anymore and, of course, they didn't since all of the Grade 2 hardware was on sale. He said that I could use a Grade 5 since it was harder and would shear cleaner than the Grade 2. Passed on the advise since I don't trust these guys very much. A personal observation with the store i.e. a collection of village idiots based upon previous experiences in other areas.

    I had the opportunity to stop at my JD dealer to ask a general question about my 4100 (Boy, the 4200 and 4300 are looking good - Hey, honey can I ..... [img]/w3tcompact/icons/wink.gif[/img]). While I was there I asked for some of the Grade 2 shear bolts and they recommended the same thing as the Quality Farm and Home store (must apologize to QHF people [img]/w3tcompact/icons/blush.gif[/img]). They gave me Grade 5 bolts with nylon locking heads. Is this correct?

    When it comes to bolt grading, my head flips to the side and I begin to drool trying to understand what the differences are.

    Grade 2 is softer than Grade 5. Grade 5 seems to be better due to the hardness of the metal (shears better) whereas Grade 2 is softer and may bend rather than shear. (This is why my head flips and drooling commenses.....)

    Thoughs, comments, recommendations?

    Terry




  2. #2
    Super Member
    Join Date
    Dec 2000
    Posts
    6,737
    Tractor
    JD 8320 MFWD, JD 6415 MFWD, FEL, and cab, John Deere MFWD 4600, John Deere 4020, John Deere 4430, John Deere 455 mower, Deutz, and Gehl 4610 perkins skidsteer

    Default Re: PTO shear pin advice.

    Terry,
    My grandfather is stern about putting the correct bolt back in for shear pins and I guess it's rubbed off on me. Much of the equipment is based on tolerable levels. If you go past these levels then you have a chance of tearing up the equipment and not just the inconvenience of having to replace a shear pin. Most equipment that I have used has a specific grade to use. I have always used what the manual calls for. I keep a supply for each piece either strapped to or in the toolbox of equipment that I have. I have never had a problem with a grade 2 shearing.

    Now that being said certainly things change over time and so do recommendations. What those guys say may be true but I'll stick with the tried and true ways until someone can show me where it has some merit rather than just someone's say so.


  3. #3
    Super Member
    Join Date
    Dec 2000
    Posts
    6,737
    Tractor
    JD 8320 MFWD, JD 6415 MFWD, FEL, and cab, John Deere MFWD 4600, John Deere 4020, John Deere 4430, John Deere 455 mower, Deutz, and Gehl 4610 perkins skidsteer

    Default Re: PTO shear pin advice.

    BTW the dealer was just out as I was having a few problems with the flywheel being too tight on the new baler and shearing pins. He told me to absolutely never use anything but the recommended bolts for it as it could cause serious damage.


  4. #4
    Epic Contributor Bird's Avatar
    Join Date
    Mar 2000
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    37,748
    Location
    Texas

    Default Re: PTO shear pin advice.

    I agree with Cowboydoc. When I don't have the technical knowledge, or enough practical experience, to be convinced that I know better than the manual, then I stay with the manual (and such is the case with shear bolts).

    Bird

  5. #5

    Default Re: PTO shear pin advice.

    Rule of thumb....with manual in hand... do what the manual states..., with no manual in hand use grade 2 bolts for shear up to 45 PTO hp, or use grade 5 bolts for 50 PTO hp or greater...

    You shouldn't have to have "a number of shear bolts on hand"..., you should install a slip-clutch on the device if that's the case.

    I don't have my charts here, but the shear strength on a grade 5 1/2" bolt is about 2-3 times that of a grade 2... so if you have the grade 5 bolt installed instead and something must give... guess what... it will be whatever the weakest component is at that moment... blade breaking, gearbox, twisting pto shaft, or maybe inside the tractor PTO drivetrain... [img]/w3tcompact/icons/frown.gif[/img]

    "You can put use the correct 15 amp fuse or stick a penny in and take your chances..." [img]/w3tcompact/icons/tongue.gif[/img]




  6. #6

    Join Date
    Nov 2000
    Posts
    386
    Location
    NW CT
    Tractor
    Kubota B2410HSD

    Default Re: PTO shear pin advice.

    Terry,

    For the size pin you're talking about, the shear strength of an SAE Grade 5 bolt is about 60% higher than the shear strength of a Grade 2 bolt. Are you a gambling man? [img]/w3tcompact/icons/smile.gif[/img]

    Grade 5 bolts are stronger, plain and simple, whether it is in pure tension, bending, or in shear. The two grades are made from similar types of steel, but the Grade 5 is quenched and tempered for strengthening. However, the ductility is comparable.

    Can you guess where I stand?

    Rob


  7. #7

    Default Re: PTO shear pin advice.

    Thank God for engineers... [img]/w3tcompact/icons/blush.gif[/img]

    Otherwise, you'd have farmboys spaning tings...[img]/w3tcompact/icons/smile.gif[/img]

    Thanks Rob!




  8. #8

    Join Date
    Aug 2001
    Posts
    472
    Location
    Central NY
    Tractor
    Kubota B7500HSD

    Default Re: PTO shear pin advice.

    John;

    Re: installing a slip clutch. I've seen that mentioned here
    before.

    How easy/expensive is that to do? I have a front mount
    snowblower on a B7500 that I had a **** of a time with
    last winter due to gravel in the driveway. Just about every
    time I had to use the blower, I broke a shear bolt. Most
    of the time, I just left it broken and used the blower as a
    plow.

    If this is a simple conversion that a dealer can do (I don't
    have the mechanical skills or tools that would most likely
    be required) relatively cheaply, it would be a great relief
    to me.

    I would assume that a slip clutch, if it encounters an object
    like a rock, would stop the auger. To get it moving again, I
    would simply have to remove the rock and the auger would
    work again.

    Out of curiousity, if installing a slip clutch is relatively simple and inexpensive, why do the manufactuers even use shear
    bolts?


    Thanks.

  9. #9
    Epic Contributor Bird's Avatar
    Join Date
    Mar 2000
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    37,748
    Location
    Texas

    Default Re: PTO shear pin advice.

    snowman, I don't know whether you can add a slip clutch or whether it would require just buying a new PTO drive shaft. As for why they use shear bolts instead of slip clutches on everything . . . usually a slip clutch is about a $100 option, so cost is undoubtedly the reason. And then a slip clutch requires just a little more maintenance than a shear bolt, so some of us prefer the shear bolts. In my own case, I don't have a slip clutch on anything, nor do I need or want one. I've never even sheared a bolt on my own equipment, so it depends on the terrain you're working and type of work as to whether you need the slip clutch. The only shear bolt I've ever sheared was on a neighbor's hay baler a few years ago.

    Bird

  10. #10

    Join Date
    Jul 2001
    Posts
    1,807
    Location
    Sharpsburg, Md
    Tractor
    John Deere 4100 HST

    Default Re: PTO shear pin advice.

    Wow - TBN to the rescue!!! [img]/w3tcompact/icons/smile.gif[/img]

    Post a message, do a little meaningful work, and grab a quick lunch and an answer appears.

    Back to the Grade 2 shear pins!!

    Thanks goes out to all of you!!

    Terry


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