Abstract: The present invention relates to the field of manufacture of miniature drills and discloses a miniature drill, which includes a drill body, a drill tip formed at one end of the drill body, and a plurality of spiral chip slots spiraling on a surface of the drill body; the chip slots include a long chip slot, a short chip slot, and a communicating chip slot, the long chip slot and the short chip slot are arranged at intervals and have the same helix angles, and the long chip slot is communicated with the short chip slot by the communicating slot.

Abstract: The present invention relates to the field of manufacture of miniature drills and discloses a miniature drill, which includes a drill body, a drill tip formed at one end of the drill body, and a plurality of spiral chip slots spiraling on a surface of the drill body; the chip slots include a long chip slot, a short chip slot, and a communicating chip slot, the long chip slot and the short chip slot are arranged at intervals and have the same helix angles, and the long chip slot is communicated with the short chip slot by the communicating slot.

Abstract: Conditions of a mechanical system driven (12) by a motor (14) can be assessed by monitoring an admittance or impedance at an input to the motor (14) over a period of time. The admittance or impedance may be determined by measuring the input voltage (22) and current (20). Variations in admittance or impedance are associated with known conditions including faults. An analyser (24) processes the admittance or impedance and provides a warning signal if a known fault condition is determined. The processing may be done using a neural processor.