Kelly is a long square or hexagonal, precision machined heavy steel bar that is supported by the swivel through the rotary table and is connected to the first joint of drill pipe in the drill string.
Straightness inspections are carried out before, during and after each machining operation. The flats are precision milled to API specifications. All milling processes are performed on specially designed rigid Kelly mills to ensure tight tolerances and high quality drive sections. Each Tianhe Kelly is furnished with a pressed steel thread protectors.