... rod are widely used in big steel mill for delivering liquid steel specially from blast furnace —MAXDRILL ... 38mm-70mm.(2) shape, carbide 3-blade type , steel cross bit , carbide cross bit ,button bit andetc ... tap hole drill rods and tap hole drill bits, according to customers' request, various tap hole ... hole drill bits are available. (1)Diameter: 38mm-70mm.(2) Shape; carbide 3-blade type, steel cross bit ...