UNIDRILL Interlocking Kelly Bar Customizable Match Various Rigs

Interlocking Kelly Bar


Application: For piling rigs for drilling in dense sand, gravel and rock


Kelly sections: Kelly bar 3-5 sections


Type: Interlocking/friction/combined kelly bar


Size:Diameter range from 355mm-930mm


Warranty: One year


Suitable Rigs: Bauer, Soilmec, Liebherr and more...





UNIDRILL® Kelly Bar In Bridge Projects



Kelly bars are key components in the execution of boreholes with hydraulic rotary drilling rigs. They transfer the torque of the rotary drive and the crowd pressure of the crowd system concurrently to the drilling tool. A Kelly bar consists of 3 – 5 telescopic tubular sections with a system of drive keys and lock recesses, welded onto their outer surfaces.

Why Unidrill?


1. Material


Why do we dare to say that our kelly bar are the best in China?


First of all, it is because of our strict control on the material. When it comes to materials, we never cut corners. The first two sections of kelly bar are made of high quality SY550. Moreover, our kelly bar adapter is forged with 25CrMo material.


2. Construction


Reinforcement Ring Structure

We have innovatively added a reinforcement ring structure for each terminal joint, which is heat-treated to effectively reduce the risk of cracking the pipe during drilling.


Kelly bar Long Guide Structure Design


The design of long guiding structure can improve the verticality of hole formation, improve the stress on the lower pipe orifice, reduce the failure rate of lower pipe cracking, improve the stability of drill pipe compression, increase the width of the retaining ring, and prevent the deformation of the pipe orifice.


Drive Rib Design


Interlocking kelly bars are indeed provided with drive ribs which are welded with lock devices in order to transfer the maximum torque to each scope. To make sure to transfer the maximum torque over the full extended length.


Shock Absorbing Spring



For springs, we normally use the same disc springs as Bauer’s original kelly bar, which has a high load capacity for all kinds of kelly bar and a service life of over 3000hr. However, considering that what spring is used depends on the pressure, we will also use spiral spring for some friction kelly bar due to the low pressure.


3. Maintenance

We will provide maintenance solutions for terminal joint, flange part, kelly box and other components. Due to the epidemic, we will have video conversations with you to guide you on the proper care and maintenance of your kelly bar.


What should I pay attention to when using the kelly bar?


  • 1. The maximum torque and pressure applied should not exceed the maximum allowable value of the kelly bar.
  • 2. The main winch wire rope, pipe and power head drive sleeve are located at the same axis.
  • 3. The mast of the drill pipe is kept vertical.
  • 4. The drill head should be aligned with the center of the hole.

How should the kelly bar be maintained?
Good maintenance and operating habits can effectively avoid damage to the kelly bar.

  • 1. Open it regularly for inspection and repair in time when wear is found.
  • 2. Regularly check the welding seam.
  • 3. Good operating habits.
  • 4. Look at the appearance, listen to the sound of pumping and pulling, feel the friction and the sense of impact of each section.


4. Quality Guarantee And Warranty

Kelly bar of Unidrill is accompanied by a one year or 2000 working hours warranty. Customer satisfaction is our first and most important priority. Our warranty policy goes above and beyond our competitors and is one of the best reasons to do business with us. We want our customers to have an exceptional buying experience every time. Our warranty policy is designed to maximise our customers’ confidence.

For Bauer, Soilmec, Liebherr Rigs And More..

We provide drill pipe customization service. You can customize the length, diameter, drill pipe accessories and even drill pipe color for your Bauer or Soilmec etc. drill rig.





Type Drilling Depth A B D Weight
(m) (mm) (mm) (mm) (T)
3 Sections Interlocking
33 13190 36200 14640 8.5
4 Sections Interlocking
52 15190 55000 16640 11.5
5 Sections Friction
58 13075 60800 14570 8.98
4 Sections Interlocking
44 13190 46700 14640 9.15
5 Sections Friction
100 22100 102800 23600 17.75
4 Sections Interlocking
64 18190 66700 19640 15.53
6 Sections Friction
68 13075 60800 14580 12.7
5 Sections Interlocking
68 15075 70800 16580 13.84
4 Sections Interlocking
44 13190 46700 14670 10.8
3 Sections Interlocking
39 15190 42300 16640 13.44
6 Sections Friction
110 20050 110000 21750 22.82
5 Sections Interlocking
82 18050 81500 19750 21.83
4 Sections Interlocking
64 18050 65500 19750 19.01
Other types can be manufactured as per customers’ demand.











The most professional R & D and production team

The core R & D, processing and production personnel are all from leading enterprises of this industry, with more than ten years of experience in design and manufacturing of kelly bars. We have provided tailor-made kelly bars and technical services for almost all the well-known brand names of rotary drilling rigs both at home and abroad.

Top quality special steel materials

Steel pipes used in our kelly bars come from the selected materials made by the first-class steel enterprises at home and abroad. The yield strength and service life are more than doubled compared with the general-purpose products, meeting the rigorous requirements in drilling hard rock and various strata.

The cutting-edge manufacturing technology

The core parts of kelly bars, such as square head, driving keys, and locking recesses, are made of imported steel by special heat treatment and surface strengthening treatment, which not only feature high yield strength, wear resistance, impact resistance, strain capacity, welding property and corrosion resistance, but also meet high reliability requirements of kelly bars in the construction of hard rock, large diameter and super deep piles.
From the strict control of raw materials to multi-layer and multi-step precise welding, we comply with strict quality standards and monitoring systems in all aspects of kelly bar production to ensure 100% high standard quality. We are also the first kelly bar manufacturer in China to provide customers with a one-year warranty.



Packing & Delivery




Kelly Bar Catalogue
(PDF,30 MB)













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