A percussion device that includes: - an input side; - an output side; - a percussion impactor; and - a percussion anvil; characterised in that the percussion device further includes at least one drive transmitter and a drive transmitter pathway; where: - the drive transmitter pathway is a circumferential pathway around a longitudinal axis of the percussion device; - the drive transmitter pathway includes at least one tooth section including a lift section and a lead section; - the at least one tooth section is essentially one wavelength of a sawtooth wave; - the lift section is inclined away from a base of the drive transmitter pathway; - the lead section is a section of the tooth section which abruptly returns to the base of the drive transmitter pathway; - the percussion anvil is attached to, or forms part of, the output side; - the output side includes an impactor shaft which is an elongate member extending above the percussion anvil; - the impactor shaft is aligned with the longitudinal axis of the percussion device; - the percussion impactor includes an impactor shaft tunnel which is a longitudinally aligned void; - the impactor shaft is a longitudinal sliding fit within the impactor shaft tunnel; - the impactor shaft and the impactor shaft tunnel have complementary cross sections configured to minimise any differential rotational motion between the percussion impactor and the impactor shaft when the output side is free to rotate; - the percussion impactor includes an impact end and a force input end which are longitudinally opposite terminal ends of the percussion impactor; - the impact end faces the percussion anvil; and - neither the impact end nor the percussion anvil are coterminous with either the drive transmitter pathway or the at least one drive transmitter; such that: - when in use, and the output side is free to rotate, the at least one drive transmitter and the drive transmitter pathway are configured to act co-operatively to transfer the rotational motion of the input side to the output side; and - when in use and either limited or no rotation of the output side is possible, the at least one drive transmitter and the drive transmitter pathway are configured to act co-operatively to increase, maintain or decrease the distance between the percussion impactor and the percussion anvil; wherein the at least one drive transmitter and the drive transmitter pathway are configured to act co-operatively to accept rotational motion from the input side and, in combination with the percussion impactor, transmit a percussive and/or rotational motion to the output side. - an input side; - an output side; - a percussion impactor; and - a percussion anvil; characterised in that the percussion device further includes at least one drive transmitter and a drive transmitter pathway; - the drive transmitter pathway is a circumferential pathway around a longitudinal axis of the percussion device; - the drive transmitter pathway includes at least one tooth section including a lift section and a lead section; - the at least one tooth section is essentially one wavelength of a sawtooth wave; - the lift section is inclined away from a base of the drive transmitter pathway; - the lead section is a section of the tooth section which abruptly returns to the base of the drive transmitter pathway; - the percussion anvil is attached to, or forms part of, the output side; - the output side includes an impactor shaft which is an elongate member extending above the percussion anvil; - the impactor shaft is aligned with the longitudinal axis of the percussion device; - the percussion impactor includes an impactor shaft tunnel which is a longitudinally aligned void; - the impactor shaft is a longitudinal sliding fit within the impactor shaft tunnel; - the impactor shaft and the impactor shaft tunnel have complementary cross sections configured to minimise any differential rotational motion between the percussion impactor and the impactor shaft when the output side is free to rotate; - the percussion impactor includes an impact end and a force input end which are longitudinally opposite terminal ends of the percussion impactor; - the impact end faces the percussion anvil; and - neither the impact end nor the percussion anvil are coterminous with either the drive transmitter pathway or the at least one drive transmitter; - when in use, and the output side is free to rotate, the at least one drive transmitter and the drive transmitter pathway are configured to act co-operatively to transfer the rotational motion of the input side to the output side; and - when in use and either limited or no rotation of the output side is possible, the at least one drive transmitter and the drive transmitter pathway are configured to act co-operatively to increase, maintain or decrease the distance between the percussion impactor and the percussion anvil;