A percussion device including an input side and an output side , where the input side is configured to be rotationally driven and the output side is configured to be rotationally driven by the input side via a drive transmitter /drive transmitter pathway combination, where at least one drive transmitter is configured to slide or roll along at least part of a length of a drive transmitter pathway , such that the percussion device further includes a percussion impactor , an impactor shaft and a percussion anvil wherein: - the impactor shaft is an elongate member extending from the output side towards the input side ; - the percussion impactor includes impactor shaft tunnel which is a longitudinally co-axially aligned void; - the impactor shaft is a longitudinal sliding fit within the impactor shaft tunnel ; - the impactor shaft incorporates one or more impactor shaft spline which is a longitudinally aligned helical spline; - the impactor shaft tunnel incorporates one or more impactor spline channel which is a longitudinally aligned helical channel in a wall of said impactor shaft tunnel ; and - the impactor shaft and percussion anvil are part of the output side ; such that in use, where the output side has restricted, or no, ability to rotate, the combination of the drive transmitter /drive transmitter pathway combination increases the distance between the percussion impactor and the percussion anvil as the interaction of the at least one impactor shaft spline within the complementary impactor spline channel causes the percussion impactor to rotate in a direction counter to the input side until the drive transmitter /drive transmitter pathway combination releases the percussion impactor , characterised in that , the percussion impactor includes at least one impactor impact tooth and the percussion anvil includes at least one anvil impact tooth , wherein each impact tooth includes an angled impact surface , such that complementary impact surfaces are configured to pass a percussive and/or rotational impulse from the percussion impactor to the percussion anvil . - the impactor shaft is an elongate member extending from the output side towards the input side ; - the percussion impactor includes impactor shaft tunnel which is a longitudinally co-axially aligned void; - the impactor shaft is a longitudinal sliding fit within the impactor shaft tunnel ; - the impactor shaft incorporates one or more impactor shaft spline which is a longitudinally aligned helical spline; - the impactor shaft tunnel incorporates one or more impactor spline channel which is a longitudinally aligned helical channel in a wall of said impactor shaft tunnel ; and - the impactor shaft and percussion anvil are part of the output side ; such that in use, where the output side has restricted, or no, ability to rotate, the combination of the drive transmitter /drive transmitter pathway combination increases the distance between the percussion impactor and the percussion anvil as the interaction of the at least one impactor shaft spline within the complementary impactor spline channel causes the percussion impactor to rotate in a direction counter to the input side until the drive transmitter /drive transmitter pathway combination releases the percussion impactor , characterised in that , the percussion impactor includes at least one impactor impact tooth and the percussion anvil includes at least one anvil impact tooth , wherein each impact tooth includes an angled impact surface , such that complementary impact surfaces are configured to pass a percussive and/or rotational impulse from the percussion impactor to the percussion anvil . <EOS>