A sliding piece in percussive boring designed to reduce the vibration and jarring effects when the downward movement of the chisel is suddenly arrested by striking the bottom of the borehole. The lower portion (which is attached to the chisel) is free to slide up and down in a slot provided in the upper part of the joint. When the chisel strikes the bottom of the hole, the slot allows the rods to continue the downward movement without being jarred by the blow of the chisel.