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's end, drive cross-section and joint are all processed and tested comform to API criterion. Features and Benefits Manufactured from AISI4145H-modified, fully heat-treated alloy steel with a Brinell hardness range of 285-341BHN and a minimum average Charpy impact value of 40ft-Ibs; Ends and drive section,IDs and connections machined and inspected to API specification; Ultrasonic inspection is performed on all section; Shipped in a protective steel -cased scabbard;