Measurements of free vibrations of drill bit held in a chuck by laser Doppler method

Abstract

The transverse vibrations of drill bits held in a chuck and plucked were studied using a laser Doppler interferometer (LDV). We found that free vibrations are generally dominated by a beat originating from the superposition of two components with similar frequencies (within a few percent), which belong to the transverse vibrations of the drill bits in the direction of the groove end and perpendicular to that. The tuning fork model gives the frequencies of the free vibrations of the 9mm diameter drill bit with an accuracy of a few percent, while in the case of thicker (10 and 12mm) drill bits it overestimates by 15-20 percent.  We also examined the effect of supporting the drill bit, pulling the drill bit further out of the chuck, and the type of tapping (blunt or sharp) on the vibration spectrum.