how to drill post holes in solid rock

Discussion in 'Misc DIY' started by klim, Mar 7, 2004.

  1. klim

    klim Guest

    I need to drill many (50 to 100) 1 1/2" diameter holes 6" deep in
    solid rock for steel T-posts for a fence and I haven't decided how to
    go about it.

    What type of bit/drill combination would be most cost effective?
    Electric drill (size?) with core bit?
    Pneumatic drill with impact bit?
    Other combo?

    The location is far from power so the job would require a portable
    generator or a compressor if a pneumatic drill was used.

    I have a 2hp 20 gallon compressor - would be sufficient to run a
    pneumatic drill to drill the 1 1/2" holes?
    klim, Mar 7, 2004
    #1
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  2. klim

    Toller Guest

    "klim" <> wrote in message
    news:...
    > I need to drill many (50 to 100) 1 1/2" diameter holes 6" deep in
    > solid rock for steel T-posts for a fence and I haven't decided how to
    > go about it.
    >

    I haven't any idea, but know enough to ask if it is granite or shale.
    Toller, Mar 7, 2004
    #2
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  3. klim

    SteveB Guest

    "klim" <> wrote in message
    news:...
    > I need to drill many (50 to 100) 1 1/2" diameter holes 6" deep in
    > solid rock for steel T-posts for a fence and I haven't decided how to
    > go about it.
    >
    > What type of bit/drill combination would be most cost effective?
    > Electric drill (size?) with core bit?
    > Pneumatic drill with impact bit?
    > Other combo?
    >
    > The location is far from power so the job would require a portable
    > generator or a compressor if a pneumatic drill was used.
    >
    > I have a 2hp 20 gallon compressor - would be sufficient to run a
    > pneumatic drill to drill the 1 1/2" holes?


    Rent a core drill?

    As suggested, it MIGHT be cheaper to have someone do it. It WOULD be a
    whole lot easier. You might be opening a bag of snakes.

    Steve
    SteveB, Mar 7, 2004
    #3
  4. klim

    DanG Guest

    Way back when some friends and I generated a bid for 8' cyclone in
    extremely rocky soil. A California company came in 40% lower than
    any other local outfits. We went out to laugh thinking they would
    not be prepared for local soil conditions. They had a heavy steel
    dome, inserted approximately 1/4 stick of dynamite. When the
    charge went off, the lid was upside down next to the hole ready
    for the next load and the hole was clean to the bottom waiting for
    the post and concrete.

    Don't ever assume the low bidder is nuts. These guys went all
    over the world setting fence.

    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    Keep the whole world singing. . . .
    DanG


    "klim" <> wrote in message
    news:...
    > I need to drill many (50 to 100) 1 1/2" diameter holes 6" deep

    in
    > solid rock for steel T-posts for a fence and I haven't decided

    how to
    > go about it.
    >
    > What type of bit/drill combination would be most cost effective?
    > Electric drill (size?) with core bit?
    > Pneumatic drill with impact bit?
    > Other combo?
    >
    > The location is far from power so the job would require a

    portable
    > generator or a compressor if a pneumatic drill was used.
    >
    > I have a 2hp 20 gallon compressor - would be sufficient to run a
    > pneumatic drill to drill the 1 1/2" holes?
    DanG, Mar 7, 2004
    #4
  5. Rent an 90 cfm air compressor and a drifter drill. Most equipmet rental
    companies rent these items. Get a drill bit to fit the drifter that is equal
    in diameter as the maximum size as your post. Then drill by going down about
    6 inches and lifting the drill to within 1" of the top of the hole. continue
    this until you reach the plan depth of your hole. Once at the bottom flip
    the lever of the air drill to blow out the hole. There are usually three
    positions for the operating lever on the drifter drill. There is one that
    shuts it off. One that drills the hole and one that blows air to the bottom
    of the hole to clean out the cuttings. It is important that when you rent
    the drill, you show rent two drill bits. One is to be used to drill and the
    other is to be used in case you lock up the first drill bit. If the first
    bit gets locked in the hole, then simply use the second bit to drill beside
    the other bit to relieve the pressure and remove the bit.
    Wear heavy duty clothing and steel toe shoes when working. Safety glasses
    are best due to the fact that the high pressure air will blow cuttings into
    your face.

    Make a plywood template that you can secure to the ground with your foot or
    other item to hold the bit in place on unlevel ground. Becareful not to let
    the plywood spin and cause injury.

    Spend some time and plan a safe work experience. Expect the work to be very
    energy consuming.
    Watch for hand injury due to the vibration of the drill.

    Good luck.

    "klim" <> wrote in message
    news:...
    > I need to drill many (50 to 100) 1 1/2" diameter holes 6" deep in
    > solid rock for steel T-posts for a fence and I haven't decided how to
    > go about it.
    >
    > What type of bit/drill combination would be most cost effective?
    > Electric drill (size?) with core bit?
    > Pneumatic drill with impact bit?
    > Other combo?
    >
    > The location is far from power so the job would require a portable
    > generator or a compressor if a pneumatic drill was used.
    >
    > I have a 2hp 20 gallon compressor - would be sufficient to run a
    > pneumatic drill to drill the 1 1/2" holes?
    R.C. Crawford, Mar 7, 2004
    #5
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