Teams should be aware that the competition drill bit provided by Baker Hughes GE has a provision to adjust its steerability (as mentioned in the bit information sheet). For more clarity, they are providing details on how to achieve it:
Bit anisotropy is a ratio of bit’s aggressiveness in axial and lateral directions. Higher bit anisotropy means higher side cutting. By changing the exposure of ovoid elements, the axial and lateral aggressiveness can be changed independently, thus changing the bit anisotropy. The provided bit has a hole on each gauge pad and one on the bit crown, in each of which an ovoid element can be installed at a configured exposure. The shipment included sufficient number of tungsten carbide ovoid elements and steel shims. Each shim is 0.025 inch thick. The installation could be done with a strong glue (e.g. Araldite 2014) (brazing would be less convenient).
Adjustment for side cutting:
- The bit without any ovoid elements installed has radial clearance of 0.150” at the gage pads (most side cutting)
- Installing ovoids with no shims will have radial clearance of 0.025” at the gage pads (reduced side cutting)
- Installing ovoids with one shim each will have radial clearance of 0.0” at the gage pads (least side cutting)
- Additional settings could be achieved, but requires the teams to build ovoid elements of varying lengths (steel is ok)
Adjustment for axial cutting:
- The bit without any ovoid elements installed has axial clearance of 0.175”+ at the gage pads (most axial cutting)
- Installing an ovoid with no shims will have no effect as the clearance will still be large (0.150”)
- Installing the ovoid with multiple shims would enable axial cutting adjustment. Since the depth of cut is very small, the ovoid will have to be exposed close to 0.0” or even stick out to engage with the rock and reduce the axial aggressiveness.
It is recommended that measurements be done to ensure desired exposures are achieved as the manufacturing tolerances come into play. Feel free to contact 2019@Drillbotics for any questions.