Modeling of dynamic behavior of multispan gundrilling shaft with coolant and its effect on straightness deviation

Abstract A dynamic model for multispan rotating gundrill shaft with thrust force and coolant pressure is proposed using rotational Euler–Bernoulli beam model (REB) through energy approach. From the numerical simulation, it is found that the 1st critical RPM of the rotating gundrill shaft increases tremendously as coolant pressure increases. The proposed model is incorporated with a straightness model. Experimental verification for the proposed model is presented. It is found that by using the combination of higher pressure (2000 psi) and rotational speed (1600 rpm), a straighter hole within industrial tolerance is achieved in gundrilling of Inconel-718.