CSC Production Square and Hexagonal Kelly

Kelly is a critical component located at the top of the drill string, available in both square and hexagonal designs. During rotary drilling operations, the kelly connects with the square bushing and the rotary bushing, transferring the surface rotary torque to the drill pipe and driving the drill bit. It also supports the weight of the entire drill string. In applications involving turbine or mud motor drilling, the kelly helps manage both the weight of the drill string and the counter-torque generated during the process.

Introduction

Continental Steel Co., Ltd (CSC) offers high-quality square and hexagonal kellys manufactured in strict compliance with API Spec 7-1 standards. The materials used are AISI 4145H modified alloy steel, fully heat-treated to achieve a Brinell hardness range of 285–341 and a minimum Charpy impact value of 40 ft-lbs. Each kelly bar undergoes full-length ultrasonic inspection to ensure structural integrity and reliability under demanding drilling conditions.

Parameter Table

Size (in) Top Connection (LH) Bottom Connection I.D. (in) Drive Section (in)
Standard O.D. (in) Optional O.D. (in) Square O.D. (in) Hex. O.D. (in) Square Hex. A B
2-1/2 6-5/8 REG 7-3/4 4-1/2 REG 5-3/4 NC26 / 1-1/4 / 3-2/7 /
3 6-5/8 REG 7-3/4 4-1/2 REG 5-3/4 NC31 4-1/8 NC26 3-3/8 1-3/4 1-1/4 4 3-3/8
3-1/2 6-5/8 REG 7-3/4 4-1/2 REG 5-3/4 NC38 4-3/4 NC31 4-1/8 2-1/4 1-3/4 4-1/2 4
4-1/4 6-5/8 REG 7-3/4 4-1/2 REG 5-3/4 NC46 6-1/4 NC38 4-3/4 2-4/5 2-1/4 5-4/7 4-4/5
6-5/8 REG 7-3/4 4-1/2 REG 5-3/4 NC50 6-3/8 NC38 4-3/4 2-4/5 2-1/4 5-4/7 4-4/5
5-1/4 6-5/8 REG 7-3/4 / 5-1/2 FH 7 NC46 6-1/4 3-1/4 3 7 6
6-5/8 REG 7-3/4 / NC56 7 NC50 6-3/8 3-1/4 3-1/4 7 6
6 6-5/8 REG 7-3/4 / / 5-1/2 FH 7 / 3-1/2 / 6-4/5
6-5/8 REG 7-3/4 / / NC56 7 / 3-1/2 / 6-4/5

Whether you're working on conventional rotary drilling or more advanced directional drilling systems, our square and hexagonal kellys are designed for durability, performance, and compatibility with a wide range of drilling equipment. With precise manufacturing and rigorous quality control, CSC ensures that every kelly meets the highest industry standards, delivering reliable results in even the most challenging environments.

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September 26, 2025