Stuck bits can be removed without barrel damage

Discussion in 'Tower, Rooftop and Antenna Installation' started by Wireless Estimator, Feb 1, 2008.

  1. Wireless Estimator

    Wireless Estimator Administrator Staff Member

    To remove a stuck bit: Disconnect the core rig from the bit. Thread a piece of threaded rod the same diameter as the bit through the hub until it hits the concrete. Then place two hex nuts on the rod and lock them against one another so that they in turn lock themselves to the rod. Turn nuts with a wrench, which will turn the rod, which will in turn push against the concrete core, pulling the bit from the hole without damaging it.
  2. Chas  Wagner

    Chas Wagner Industry Observer

    This is good advice, but don't be sure it will work every time! I've had some core issues with very large core sizes at depths beyond 20' below grade through large pad foundations.
    I've had drillers fabricate pulling shafts from soil anchor rod with a flip pin on the end [cut a slot into the end of the rod and drill a hole through it, then install a smaller diameter rod drill it to accept the pin, it will spin and become perpendicular once inside the core bit] and pull core cans out using anchor test rigs at psi ratings well into the kips you'd expect to see on large diameter guy wires and nearly at the kips we were to test the proposed soil anchors to! Finding a 1-1/4" coarse thread rod is challenging too. You usually end up using anchor shaft.

    The best advice for preventing stuck bits is clean the core hole often , don't try removing too large of a slug section [ I've seen 6' length x 6" diameter bits ]. Good water pressure will help flood the sediments up from deeper holes too if the rig is running and pressure on the core bit is relieved for a few minutes now and then. And most important use a driller experienced in performing your type of coring, especially if it's going to be deep.

    I hope this helps someone.
    We were lucky to have an awesome driller who was quick on his feet. We lost very little time going through this on a Seattle project where we needed to install soil anchors through and below a monopole's pad foundation

    Chas Wagner
    Project Manager
    Certified Welding Inspector
    Tower Field Services Group
    Morrison Hershfield Corporation
    404 / 787 - 6237 Mobile
    734 / 293 - 8901 Efax

Share This Page