Technical Data

Rotary Shoulder Connection 

A structural member that requires adequate make-torque to achieve 100% of its strength. The most common cause of connection failure or damage is insufficient torque applied during make-up.


Pin Stress-Relief feature

Removes the unengaged threads near the pin shoulder and provides large radii for smoother flow of stresses around corners. To mitigate the notch effect, all threads of the pin must be engaged with threads from the inbox. Considering the length of the box counter bore and the starting thread chamber; API specifies the relief groove to be one inch in length. Note: This feature is not recommended for some small connections


Bore Back Box Stress-Relief

A long, cylindrical bore machined into the box to provide relief from bending stress. The unengaged threads in the back of the box are machined out, removing the notches and subsequent stress rises that are otherwise created. The length of the cylinder section provides increased flexibility for this high-stressed area. Note: This feature is not recommended for some small connections.



The application of a phosphate coating that provides a barrier between the metallic surfaces of the pin and box to prevent galling until connections become work hardened. The porous finish also helps retain the thread compound, ensuring proper lubrication to the mating surfaces. A phosphate coating is to be applied by vat-dipping or spray-on solution and can be done at Wood International’s Free Zone facility.


Tubular Repair Services

 Connection recuts are the most common type of tubular repair. The process is similar for drill collars, drilling tools, rotary Kellys and other tubular products where the connection is the weakest part of the member. The procedure requires that 4 to 6 inches of material to be removed depending on the connection type and its features. Enough material must be removed to ensure that the damaged area (near the base of the box or pin) is not part of the newly recut connection. Most rotary shoulder connections can be recut and repaired at Wood International’s Free Zone facility. Repairs are completed and checked using API calibrated lead and taper gauges. The recut connection is then phosphate coated. A costumed thread protector is installed before leaving the shop. Note: the recut connection should be handled and broken in using the same procedures as any newly manufactured connection.


Chase and Face is a procedure used to repair the connection on tubular products drill pipe and Hevi-Wate and can be done at Wood International Free Zone. Here, only enough material (approximately one-inch) is removed to ensure that new threads and a seal face are cut into the tool joint. Lead, taper, size, and bevel diameter are all checked using calibrated gauges. Note: The new connection should be handled and broken in using the same procedures as any newly manufactured drill string member.


Tool Joint build-up is an industry-accepted procedure to extend the service life of drill pipe. Tool joints that meet minimum recommended length criteria can be professionally restored to their original OD at Wood International Free Zone. A properly rebuilt tool joint will yield a connection with the same OD, seal face area, bevel diameters and recommended make-up torque as a new tool joint.


Wood International Free Zone adheres to the following processes and parameters to ensure trouble free life of a rebuilt tool joint:

  •  The depth of the heat-effected zone must be prevented from entering the threaded area. Only tool joints with a minimum shoulder width of 5/32” can be considered for rebuild.
  • Wood International Free Zone uses a proprietary blend of wire-flux that provides a build-up material with an optimum combination of yield strength, wear resistance, ductility.
  • All existing hard metal is removed.
  • Maximum build-up limits will not be exceeded.
  • Preheat and post heat cycles are carefully monitored to ensure that mechanical properties of the tool joint are maintained and adequate post weld stress relief is accomplished.
  • The tool joint is machined to its finished diameter and the connections re-machined.

A variety of hard band materials can be applied following the rebuild process to add additional life to the tool joint. Wood International Free Zone uses Armacor “M” for its hard banding material. Tungsten is available upon request.A Wood International Free Zone representative can evaluate your downgraded tubulars to help determine which joints are repairable and at what cost.


Stub Welding Ends on Drill Collars and Specialty Tools (Stubbing)

When drill stem members become too short, box weak from OD wear, or pin weak from ID wear, they can be put back into service using a process referred to as stubbing. Smith Services is the industry specialist at stub welding new material to the ends of worn tools and cost effectively restoring the mechanical properties back to acceptable requirements.
Stubbing should be considered when:

  •   Repeated reworking of connections has left the tool too short for use.
  •   Outside wear on the tool has reduced the bending strength andtorsional strength of the box.
  •   Enlargement of the bore by erosion has reduced the bending strength and tensile strength of the pin.


Tools to consider for stubbing:The following is only a partial list of drilling tools that can be considered for the stub-welding repair.

  • Drill collars
  • Heavy wall drill pipe
  • Stabilizers
  • Roller reamers
  • Hole openers
  • Shock subs
  • Rotary kellys 

A Wood International Free Zone representative should be contacted for stubbing recommendations on these and other drilling tools. Wood International Free Zone uses a proprietary blend of weld material and flux to produce a weld deposit with 55,000-psi yield strength, while maintaining optimum hardness and ductility. Strict attention is given to the preheating of parts, welding processes and post heat cycles. Automated stubbing units ensure high quality stub welds and conformance to requirements on every stub weld. Consider stub welding as a method to prolong the life of your drilling tools.


Rotary Kelly Repair
The Rotary Kelly is the drive link between the surface power of the rig and the drilling ability of the bit. When Kelly wear does become appreciable, ship it to Wood International Free Zone where it can usually be repaired and returned to service.
The following conditions can be repaired at Wood International Free Zone:

  • Connection Damage: The upsets on each end of the Kelly aremanufactured with sufficient length to allow the connections to be recut a number of times.
  • Rounded Drive Corners: This condition can be repaired in one of two ways. The first and easiest to accomplish is to reverse the ends. This process enables the unworn side of the corners to be placed into service. The second is to re-machine the drive flats to a smaller non
  • API size: This process may require special milling equipment notavailable in most field service centers. It should be noted that when this procedure is selected, special rollers must be purchased for use with the modified Kelly and recalculation of the Kelly tensile strength is required.

Kelly life can be extended significantly by implementing the following recommendations:
1. Always use a saver sub to reduce thread wear and damage on the
lower connection.
2. Do not transport the Kelly until it is placed in its scabbard.
3. Lubricate the drive surfaces of the Kelly to permit it to slide freely
through the drive bushing.
4. Inspect frequently for indications of fatigue damage and stay alert to
changing wear patterns on the Kelly flats.

We offer quality application of hardband OD-wear protection on drill collars, drill pipe, heavy wall drill pipe, and other drilling tools used in open-hole applications. An automatic, metal-arc, inert gas shielded, consumable electrode process is used with closely controlled preheat and post heat. When hard band is replaced it is necessary to remove the existing hard band prior to the application of the new hardmetal. Conventional hardband material consists of granular tungsten carbide fed automatically into the molten puddle to obtain uniform distribution of the tungsten carbide particles. The resulting deposit of the weld is flush to 1/32” (unless otherwise specified) above the OD of the drill collar or tool joint. A selection of casing friendly, non-tungsten carbide, hardband from industry-approved suppliers is also available through Wood International Free Zone.


Heavi-Wate Drill Pipe: Hardbanding is recommended for the pin and box tool joints, as well as the center upset wear pad section. The standard application consists of: 5” of hardmetal placed flush with the OD on the pin tool joint, 5” of hardmetal placed flush with the box tool joint OD (4” on the tool joint and 1” on the taper) plus fingers applied to the tapered section of the box tool joint to prevent fluid undercutting. The center upset wear pad section is provided with two 3” long bands applied to the OD to prevent wear to the center of the tube. Spiraled Hevi-Wate will require tool joint hardbanding only.

Drill Collars: There are three standard options for applying hardband to drill collars; Type A, Type B, and Type C as indicated in the Drill Collar Hardbanding Options reference. Variations of these options are available upon request. Please consult with a Wood International Free Zone representative for more information.
Note: Drill collars smaller than 4 ¾” OD cannot be hardbanded due to wall thinness on smaller diameters.


Other Machine Shop Services
There are a number of other valuable services offered by Wood International Free Zone that include but are not limited to the following:

  •  Turn down drill collar diameters
  •  Manufacture and repair of crossover subs, pup joints, and saver subs
  •  Down hole tool repair and rebuild
  •  Stabilizer redress and repair
  •  Custom repairs