A down-hole hammer comprising a drill bit (10) and a drive collar (11) with an interconnection therebetween for causing rotation of the drill bit upon rotation of the drive collar. The drill bit (10) comprises a drill bit head (13) and a shank (19), the drill bit head (13) defining a cutting face (15) and having a circumferential shoulder section (17) adjacent the cutting face (15). The shank (19) extends from the shoulder section (17) in the direction away from the cutting face (15). The interconnection between the drill bit (10) and the drive collar (11) comprises a spline assembly including at least one spline (43) on the shoulder section (17) for mating engagement with at least one counterpart spline (63) on the drive collar (11) to provide a drive coupling therebetween while also allowing the drill bit (10) to slide axially within the drive collar (11) to perform a percussive action.