Twin Bolts On A Post Hole Digger??
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Thread: Twin Bolts On A Post Hole Digger??

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    Twin Bolts On A Post Hole Digger??

    I have a New Holland 906 PHD that I impulse purchased several years ago,,,
    the PHD was new, the paint is still on the auger teeth.

    Well, we went to assemble it, everything was going good,, then,,,
    the auger has two grade 5, 1/2X3 bolts to hold it on the gearbox.

    My Ford PHD has a single, simple grade 0 shear pin, I believe it is 1/2"

    I have only sheared that pin a half dozen times in drilling hundreds of post holes.

    A funny note,, on the boom the PHD has a sticker that specifies 1/4" X 2.50" grade 5 as the shear bolt.
    It even shows a grade 8 bolt head, and says DO NOT use grade 8

    The PHD came with the 1/2" grade 5 bolts, they are even painted the same gray color as the auger,,,
    so I think the 1/2" bolts came from New Holland.

    I really want that bolt to be able to shear,, we have LOTS of rocks,,,,
    and they are JUST the right size to catch and hold the auger.

    I kinda doubt that NH would use two 1/2" bolts,, just for shipping purposes,,,

    I am thinking about switching to a single 1/2" grade 0 bolt.
    What do you think!!??

    The bolts are Item 2,, they show the washer (Item 4) but, they do not show the nut,,,



    The parts breakdown for the bolt simply says,,, "Procure Locally"
    Some of the tractors include JD 4105, JD 855, JD 650,,,, and,,, the IH 584 4WD
    My favorite attachment is the homemade landplane,,, EVERYONE needs one of those!!

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    Bubber's Avatar
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    I thought all augers used two bolts to hold them onto the gear box?

    Anyway, my county line PDH has the shear pin on the PTO shaft, not the auger shaft.

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    wingrider's Avatar
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    My Everything attachments PHD has two bolts to hold the auger on, but the shear bolt is what is number 6 on your picture.
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    I did not look at the PTO shaft,, that may be the shear bolt??
    Some of the tractors include JD 4105, JD 855, JD 650,,,, and,,, the IH 584 4WD
    My favorite attachment is the homemade landplane,,, EVERYONE needs one of those!!

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    I would definately start small and work up. Meaning I would use 1 grade 5 bolt to start with and see how it goes. If you keep shearing that then maybe add the second one.

    Like you say - you need to adapt the shear strength to your own use.
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    First rule is always do what the manufacturer says.

    A 1/4 in grade 5 bolt has a shear strength of about 3500 lbs at the shank. Two would be 7000 lbs. A single 1/2 inch steel shear pin is about 5000 lbs.

    1/2 in grade 5 bolts are about 17000 lbs each at the shank, so two would be 34000 lbs and that "seems" really really high. If the manufacturer says use two 1/4 in bolts, then that is what I would do, though the idea of allowing that much slop in the auger doesn't seem right either.

    Why not just give NH a call to confirm?

    Al
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    Bubber's Avatar
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    Quote Originally Posted by CADplans View Post
    I did not look at the PTO shaft,, that may be the shear bolt??
    I can't post a picture due to the forum issues, but yes, check the bolt that holds the pto shaft to the gear box. That is the shear pin on mine.

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    I'll go along with Bubber and Wingrider. The shear bolt is #6 on my PHD. Here is a SpeeCo manual for an auger similar to yours, also showing your #6 as the shear bolt.

    It's handy having the shear bolt on the PTO shaft. When you break a bolt, you can still lift the auger out of the hole and drive back to the shop to get a new bolt. I bet many of us have made that trip a few times.
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    Quote Originally Posted by AlKozak View Post
    First rule is always do what the manufacturer says.
    Why not just give NH a call to confirm?

    Al
    The NH 906 PHD was out of production when I purchased it.


    I stopped at the local NH dealer, inquiring about another auger, when I first got it,,
    they acted like I had two heads!!
    Some of the tractors include JD 4105, JD 855, JD 650,,,, and,,, the IH 584 4WD
    My favorite attachment is the homemade landplane,,, EVERYONE needs one of those!!

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    Well,, the shear pin bolt is on the PTO shaft, at the input to the gearbox.

    The PHD had laid in the weeds for several years,, I decided to replace the PTO shaft,,
    rather than fight with all the rust on the end that connects to the tractor.

    Luckily, when I went to TSC,, I got a sack of replacements,,
    we popped a LOT of them, digging eleven holes for apple trees.



    I wish there was an easier way to deal with rocks,, they are not huge,,
    usually the size of a football or less,, mostly baseball to softball size.

    I almost think a post driver would be best to drive the rocks out of the way,,,
    Bubber likes this.
    Some of the tractors include JD 4105, JD 855, JD 650,,,, and,,, the IH 584 4WD
    My favorite attachment is the homemade landplane,,, EVERYONE needs one of those!!

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