Abstract: To clean boiler tubes, a hammering device for shaker rods comprises a series of hammers mounted on a horizontal shaft for vertical rotation. The hammers are moved clockwise around the shaft somewhat less than 180.degree. from the face of the rod, and then released circumferentially around the shaft axis to fall by gravity in anticlockwise direction, thereby hitting the surface of the shaker rod in a straight line. The hammer comprises a hitting surface and a support shank on which a piece of lug is installed parallel to the hitting surface. To move the hammer, a cam fixed to the shaft engages eccentrically the lug so the cam releases the lug at 100.degree. to 130.degree., that is somewhat less than a half turn. The lug is provided with an outer rotating ring. The hammer impact surface defines a cam such that an apex point faces the impact transfer axis of the shaker rod in a series of positions of hammer varying between -2.degree. and +8.degree..