earth screw anchors 1) Keep the thickness of screw flights with 3 mm or more . 2) Use the auto welding machine Product Name : earth screw anchors We are the leading manufacturing of screw flights and ground screw in China . 1) Keep the thickness of screw flights with 3 mm or more .(2) Use the auto welding machine weld the screw flights together with the tube.(3) Our capacity is 1000 pieces per ...