Experienced diamond drillers are always looking to get the best drilling performance and longest life from their drilling equipment. Sometimes core bits get damaged before they’re even used. After careful deliberation over choosing the right bit and the best core bit configuration, no one wants to ruin a bit before you start drilling. Let’s look at some problems that can happen above ground when you’re adding or changing a new core bit.
Careful with the pipe wrenches
Sometimes another tool can cause damage to the core bit, like your pipe wrench. Try to usee a proper, full grip outer tube wrenchwhen installing the core bit. In absence of this, a regular pipe wrench can be used. You should always pay attention to where you grip the core bit with a pipe wrench. Too close to the top and you can damage the matrix which is made of special metal alloys. Gripping it too close to the bottom can be dangerous as the bit is thinner near the threads.
Beware of jaws
There are two sets of jaws you need to be cautious with: the jaws on the drill rig chuck and the jaws on the rod holder. By being impatient or rushing to change the core bit, you can catch the side of your bit on the jaws of either one. A simple knock, or bump can damage the teeth of the crown and ruin the bit, and it happens often.
The core bit can get crushed by the jaws of the rod holder or chuck as well. Make sure you don’t use the chuck to force the core barrel.
Careful with the rod holder
Make sure the rod holder is locked open when you are trying to pass the core barrel through it to the casing. Otherwise, lateral pressure on the core bit can distort its shape from round to oval. Once distorted, the core bit will cut a smaller core sample. If the core sample is too small the core lifter spring will not grip the core and it will stay in the hole. Time is money and you want to avoid wasting time.
Do it by hand
As mentioned above, you should never use the hydraulic force of the chuck to force the core barrel through the rod holder and down into the casing. Ideally, you should do this by hand. Have the core barrel suspended by the hoisting cable so you can guide it manually to the rod holder and through to the casing. If you align the core barrel correctly, the core bit will not catch on any edges and you will not damage the crown.
The perfect core bit for your particular drilling operation can be expensive so ruining it before you get any core sucks big time. The cost of operations will rise if your cost per meter is too high. Yet way too often, my technical team and I see high quality core bits ruined before they have a chance to drill. Patience and a little knowledge can help enormously. Keep in mind that you can also destroy a core bit on the way down the bore hole and at the bottom. We will look at what to avoid in these situations in upcoming blogs. In the meantime, remember that technical advice is always available from our technical crew.