One of the responsibilities of a directional driller is to correctly grade a bit after it has been used in a drilling operation. Grading bit by IADC classification a used bit is important because it determines whether or not the bit can be re-run or a back up is picked up for the 2nd run.

The IADC Classification system, the IADC (International Association of Drilling Contractors) developed an eight-point dull grading system to enable drillers and bit manufacturers to evaluate a drill bit’s performance. This eight-point system is described below and is used to assess bit damage on both tricones and fixed cutter bits. It does not apply to drag bits.

Mastering the art of dull grading according to IADC standards is crucial. It allows engineers and sales personnel to communicate effectively and determine whether a drill bit suits the intended application or if an alternative is necessary.

The format for dull grading a bit is as follows;
-Inner teeth.
-Outer teeth.
-Primary dull characteristic.
-Location.
-Bearing.
-Guage.
-Secondary full characteristic.
-Reason for POOH.

The grading for TCR bits and PDC bits have slight differences (the most obvious being TCR bits have bearings in the cones and PDC bits not having any moving parts and as such have no bearings)