Effect of different drill bit geometries on the stability of the drilling process

Document Type



Master of Science (MS)


Mechanical Engineering

First Advisor's Name

Diana M. Rincon

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Ibrahim Nur Tansel

Third Advisor's Name

Cesar Levy

Date of Defense



The purpose of this study was to determine the effects of different drill bit geometries on the stability of the drilling process, based on a torsional-axial coupling model. Parameters such as number of cutting edges, helix angle and length were varied for this purpose.

The analysis was performed using a mathematical model, where the coefficients of the model were obtained experimentally by calculating the cutting forces and using modal analysis. This provided stability lobes for the four types of drill bits used, where free chatter zones were identified. These results, in conjunction with simulations performed in Matlab®, were used to run drilling experiments and validate the model. The results of this study showed that increasing the number of cutting edges or the helix angle, allowed increments in the removal rate of material. On the other hand, increasing the drill bit length has the opposite effect and reduces the removal rate of material. The model was successful predicting axial vibrations close to the blimit.



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