Kelly is the drive part of whole drill stem, it has two types, square kelly and hexagonal kelly and all of them are manufactured comfort to API Spec7-1 and SY/T6509-2000 criterion. Our� Square& Hexagonal kelly are made from AISI 4145H modified alloy bars that are quenched and tempered full length. After such heat treatment, its brinell hardness can reach 285-341. Kelly end, drive cross-section and joint are all processed and tested comform to API criterion.
