CAMTOP Rotary Kelly
Square & Hexagonal Kelly Bars — API Spec 7 & NS-1 Certified
The CAMTOP Rotary Kelly is the primary drive component of the rotary drill string, transmitting torsional energy from the rotary table to the drill bit at the bottom of the hole. Precision-machined from AISI 4145H modified alloy steel, fully heat-treated with Brinell hardness 285-341 and Charpy impact minimum 40 ft-lbs. Available in square and hexagonal configurations from 2-1/2″ to 6″ drive sections.
AISI 4145H Modified
API Spec 7 & NS-1
Square & Hexagonal
Product Overview
Kelly is the drive part of the whole drill string, transmitting the torsional energy from the rotary table to the bit in the bottom of the hole. The CAMTOP precision-machined Kelly is a heavy square or hexagonal steel bar supported by the swivel through the rotary table and connected to the first joint of drill pipe in the drill string.
CAMTOP Kelly has been approved by the NS-1 certification. Straightness is the key manufacturing process — straightness is checked before, during, and after each machining operation. Flats are precision-milled to API and NS-1 specifications. Milling is performed on specially designed rigid kelly mills. Each CAMTOP Kelly is finished with pressed steel thread protectors. Shipped in a protective steel-cased scabbard.
Technical Specifications
| Drive Section (in) | I.D. (in) | Top Connection (LH) | Bottom Connection | Approx. Wt (lbs/ft) |
|---|---|---|---|---|
| Square Kelly | ||||
| 2-1/2″ | 1-1/4″ | NC26 (2-3/8″ IF) | NC26 (2-3/8″ IF) | 5.3 |
| 3″ | 1-1/2″ | NC31 (2-7/8″ IF) | NC26 | 8.2 |
| 3-1/2″ | 1-3/4″ | NC38 (3-1/2″ IF) | NC31 | 11.4 |
| 4-1/4″ | 2-1/4″ | NC46 (4″ IF) | NC38 | 18.0 |
| 5-1/4″ | 2-13/16″ | NC50 (4-1/2″ IF) | NC46 | 25.3 |
| 6″ | 3-1/4″ | NC56 | NC50 | 32.6 |
| Hexagonal Kelly | ||||
| 3″ | 1-1/2″ | NC31 (2-7/8″ IF) | NC26 | 8.2 |
| 4-1/4″ | 2-1/4″ | NC46 (4″ IF) | NC38 | 18.0 |
| 5-1/4″ | 2-13/16″ | NC50 (4-1/2″ IF) | NC46 | 25.3 |
* Left-hand (LH) top connections standard per API. Custom sizes and lengths available upon request.
Key Features
AISI 4145H Modified Alloy Steel
Fully heat-treated with Brinell hardness 285-341 and minimum average Charpy impact value of 40 ft-lbs at room temperature — guaranteed at every distributed 16 points in any cross-section.
API Spec 7 & NS-1 Certified
Ends, drive sections, IDs and connections machined and inspected to API and NS-1 specifications. Full-length ultrasonic inspection standard.
Precision Milled Flats
Flats precision-milled to API specifications on specially designed rigid kelly mills. Straightness verified before, during, and after each machining operation.
Steel Thread Protectors
Pressed steel thread protectors on all connections. Shipped in a protective steel-cased scabbard to prevent transit damage.
Square & Hexagonal Options
Hexagonal kelly provides 6 contact points vs 4 for square — smoother torque transmission and reduced bushing wear. Ideal for deep/high-torque drilling.
Custom Metallurgy Available
Special lengths, connections, and hardbanding options available. Non-standard metallurgy for sour service or high-temperature applications upon request.
Ordering Information
When ordering CAMTOP Rotary Kelly, please specify:
- Kelly Type: Square or Hexagonal
- Drive Section Size: 2-1/2″ to 6″
- Overall Length: Standard 40 ft or custom
- Top Connection (LH): NC26 through NC56
- Bottom Connection: Standard or custom
FAQ
Q: Square vs. Hexagonal — which should I choose?
Hexagonal kellies provide 6 drive contact points for smoother torque transmission and reduced bushing wear — ideal for deep or high-torque drilling. Square kellies are more economical and widely used in standard applications.
Q: What material are CAMTOP kellies made from?
AISI 4145H modified alloy steel (chromium-molybdenum), fully heat-treated to BHN 285-341 with Charpy impact 40 ft-lbs. The premium material provides the optimal combination of strength, toughness, and wear resistance.
Q: Why is the top connection left-hand threaded?
Left-hand thread is a safety standard — during normal right-hand rotation for drilling, the top connection tightens rather than loosens, preventing accidental unscrewing from the swivel or top drive.
Q: What inspections are performed?
Full-length ultrasonic inspection, dimensional verification, hardness testing at distributed points, thread gauge inspection, and NS-1 certification documentation included with each kelly.
Order CAMTOP Rotary Kelly
Contact our sales team for pricing, availability, and custom configurations.
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