Trouble Shooting Diamond Core Bits
Glazing (bit stops drilling or is very slow)
CauseToo much feed pressure.
RemedyOpen bit with abrasive material (sand pot, concrete block, chop saw blade). Reduce feed pressure. Use of an ammeter will help to control speed and pressure.
CauseAggregate is too hard.
RemedyUse a softer bond.

Bent Segments
CauseToo much feed pressure and not enough water.
RemedyRepair the bit if possible. Ease up on feed pressure and increase water flow.
CauseAggregate is too hard.
RemedyUse a softer bond.

Lost Segments
CauseSteel reinforcing rod.
RemedyEase up on feed pressure (watch ammeter). Use a higher quality bit and increase the water flow.
CauseSteel reinforcing rod.
RemedyEase up on feed pressure (watch ammeter). Use a higher quality bit and increase the water flow.
CauseNot enough water to properly cool the bit.
RemedyIncrease water flow.
CauseDrill rig is not properly anchored.
RemedyThere are three ways of anchoring a rig - standing on the rig is not one of them!

Core Hangs Up
CauseNot enough water to remove slurry.
RemedyRemove bit and drive core out with a spike through the hub. Increase water flow.
CauseCore barrel is dented because of hammering on it to remove hung up cores.
RemedyRepair the barrel and increase water flow.

To Remove a Stuck Bit
  1. Disconnect the core rig from the bit.
  2. Thread a piece of threaded rod the same diameter as the bit (5/8-11 or 1-1/4-7) 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.
  3. Turn the 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.