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Thread: DIY post hole digger -- good idea / bad idea?

  1. #1
    Join Date
    Oct 2002
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    1,738

    Default DIY post hole digger -- good idea / bad idea?

    Just want to preface by saying I don't own a post hole digger -- nor do I think
    I really need one -- though one sure would be handy to have. I'd probably
    put up more fencing than I do if I had one.

    Anyway, never used one before.. I'm talking PTO / tractor mount digger.

    What I do have is:
    1. access to a tractor. PTO i think is 580-600something RPM in low gear
    2. a nice big gearbox, 25:1
    3. an interest in fabricating a helix / screw.

    Never fabricated a screw/helix before. But I've got M. Klotz's helix program and
    a bunch of 1/8" sheet stock.

    Am thinking might make for a fun project. However:

    1. I'd be using mild steel for the screw
    2. soil here is pretty rocky. not big pieces.. well.. maybe 3" at the absolute biggest

    I think I'd be making some kind of boom with a pivot to hang the gearbox, then the 3 point
    hitch, the screw of course, and some sort of protection from the spinny bits.

    mild steel screw a bad idea?
    homemade post hole digger a bad idea?

    any thoughts welcomed. again, just thinking might make for a fun (and useful) project, but
    I've got plenty of others on 'the list' if this is a no-no.

  2. #2
    Join Date
    Apr 2009
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    Ashburton, near Christchurch New Zealand
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    Default

    I have seen a lot (dozens maybe) home made post hole diggers. Most seemed to work OK.

  3. #3
    Join Date
    Aug 2002
    Location
    Albuquerque
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    I've been "toying" with the idea of a 1.5 to 2 inch one for use with a 1/2" heavy
    duty electric drill to "punch holes" in the caliche here. Would need to be about
    18 to 24 inches long. Any idea if it would work????
    ...lew...

  4. #4
    Join Date
    Sep 2012
    Location
    Wellington county Ontario Canada
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    IMO, the tip and teeth should be hardened, 1/8" maybe a bit light in rocky ground?
    I had to make a helix in the biodiesel boiler I made to force the liquid to travel around the flue pipe on its way through the boiler. I just flame cut a bunch of 14" washers with a 6" inner hole (same dimension as the flue pipe) out of 1/8" mild steel and then cut a slit through them so I could stretch them out to the size helix I wanted then welded them to the flue before dropping the water jacket over it all.
    I was worried that I would have to do some fancy grinding/calculating to get them to go around the flue pipe after stretching them out but it all worked out fine with just using the OD of the flue for the inner hole dimension in the flat washer....
    As far as guarding, other then the PTO shroud I have not seen any type of guarding for the auger, my dads 75 year old neighbour lost his arm to the shoulder with his post hole auger just last spring, it got stuck and he tried to lean on the top of it I guess when it caught his coat and removed his arm, he was lucky to be able to make it back to his house to call an ambulance before bleeding out...
    Good luck!
    Jon

  5. #5
    Join Date
    Jan 2010
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    Germany
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    In my lifetime I have personally built and supervised being built hundreds of miles of fence. From post and rail, pipe and cable, barbed wire, woven wire and probably a few other types that I can't think of now.

    I have owned just about every type of device to put a fence post in the ground. A hydraulic driven auger works pretty good in medium soil. They are easily reversed. You will need quite a lot of HP to be effective.

    1/8 inch for the auger blades will not be heavy enough in any kind of rocky soil. What ever you do make sure you have a reverse on the auger. If you bore down in anywhere close to a tree or football size rocks or bigger you will stick the auger. Then you will have to dig it out by hand. No fun at all.

    You will have to hardface the tip and edges of the auger. You are a good fabricator so the mechanics, frame and such will be no problem. Build it stronger than you think is necessary.

    I have a hydraulic hammer that I use to punch holes in the ground here on my farm. If the soil is not too rocky I drive the posts in with a flat faced chisel. If it is rocky then I have a custom forged 1 meter long pointed chisel to poke a hole. It takes me about 10 seconds to put a hole anywhere on my farm!
    How to become a millionaire: Start out with 10 million and take up machining as a hobby!

  6. #6
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    Jul 2007
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    Central Oilberta
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    Quote Originally Posted by Black Forest View Post
    ............. you will stick the auger. Then you will have to dig it out by hand. No fun at all. ...............

    If you stick the auger by screwing it underneath something, you should be able to disconnect the drive head and put a bar with a long cheater pipe on it and unscrew the auger from the obstruction. Guys that want screw pilings removed sometimes do that if they want the piling removed and don't have the means to get a installation unit to come do it.
    Design to 0.0001", measure to 1/32", cut with an axe, grind to fit

  7. #7

    Default

    Quote Originally Posted by Black Forest View Post
    I have a hydraulic hammer that I use to punch holes in the ground here on my farm. If the soil is not too rocky I drive the posts in with a flat faced chisel. If it is rocky then I have a custom forged 1 meter long pointed chisel to poke a hole. It takes me about 10 seconds to put a hole anywhere on my farm!
    That's how all the fencing rigs round here work that the farmers use. I was looking into repurposing a old hydraulic hammer and its suprisingly little fabrication, just something to slip over the top of the post to stop it splitting with the force as its driven home. I never did it because we found we could just push the posts in using the rear bucket on my jcb backhoe, but it is nigh on 8 ton. They either go in or shatter in spectacular fashion...

    I wondered also about taking a commercial petrol driven double handheld auger ready made and building a frame for it that mounted in place of the rear bucket. Theyre surprisingly cheap to buy now.

    If you still want to make it from first principles for the learning please ignore the above

  8. #8
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    Jul 2005
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    Chester, NH
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    Sounds like you want to make the helix, but thought I would add that you can probably find some bits of used auger flighting from a local grain elevator or farmer. Typically, when it is time to replace flighting, the edges are worn to razor sharpness but there is still quite a bit of meat left near the center. You would want something in the 12-24" range, I expect. That means looking on a big farm or elevator - a farm with a couple of bins is unlikely to have an auger remnants that large. 6"-8" are the most common size for small operations and when they wear out there isn't much left to work with.

    Also, I suggest bolting on a cutting edge. Make the cutting edge stout, hardface it and use recessed (e.g. carriage) hardened bolts/nuts. This will allow you to replace the cutting edge as it dulls or is damaged by rocks, etc. Keep in mind that the flow of dirt, rocks and sand will wear out parts - doesn't take long for an exposed bolt to be worn down to where it breaks easily.

  9. #9
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    SW Michigan
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    I've seen many butlt with car/truck rearends.
    You can lead people to knowledge but you can't make them think.
    "Lead, follow, or get out of the way."-Thomas Paine

  10. #10
    Join Date
    Sep 2004
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    Oregon Coast
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    IF your ground is that rocky, I think your going to need a pretty big rig, an a tough one. I don't know where you live, but if at all possible I think you should try to rent one and see if you can even use a post hole digger.
    _____________________________________________
    Mel Larsen
    I would rather have tools that I never use, than not have a tool I need.

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