Kellys are manufactured with one of two drive configurations, square or hexagonal. Square kellys are furnished as forged or machined in the drive section. Hexagonal or fully machined square kellys are machined from full length quenched and tempered round bars. Square Kelly and hexagonal kellys are fabricated as per requirements of customers. The kellys are made of AISI 4142H-4145H forged or rolled alloy structural steel. Quenching plus tempering thermal treatment will be conducted over the whole length. Its Brinell hardness can reach 285-341 on the basis of such thermal treatment. Charpy impact energy: >or =54J. The formulated process can ensure that the misalignment of the hole reaches the standard wall thickness. Kelly bars are manufactured according to API-7-1 Spec.