A cooling tube for an arc plasma torch, comprising an elongate body with an end which can be arranged in the open end of an electrode, and a coolant duct extending therethrough, characterized in that at said end there is a bead-like thickening of the wall of the cooling tube pointing inwards and/or outwards, and an arrangement of a cooling tube for an arc plasma torch, comprising an elongate body with a rear end which can be releasably connected to an electrode holder of an arc plasma torch, and a coolant duct extending therethrough, and an electrode holder for an arc plasma torch, comprising an elongate body with an end for receiving an electrode and a hollow interior, and characterized in that on the outer surface of the cooling tube at least one projection is provided for centring the cooling tube in the electrode holder.