Boart Longyear

Boart Longyear^TM offers three types of threads that are specifically designed for various drilling applications: Cylindrical, Conical and Twindrive.  Both casing and inner drill rods are offered in both left and right hand threads.  Industry standard API style threads are available as part of our DTH rod offering. This tapered thread form is utilized as the inner rod for rotary and DTH drilling applications.

The number of thread starts vary depending upon the size of the tooling, the application of the tooling and the type of thread utilized.  The thread length varies by casing diameter and thread type.

Cylindrical Threads

Cylindrical threads are characterized by a parallel wall design which means that the casing or rod must be completely unscrewed prior to separating the joint.

Cylindrical threads are the most common threads utilized for reusable overburden rotary-percussive casing and inner rods.
For rotary-percussive casing, all cylindrical threads are single-start up to 88.9 mm and triple-start for larger diameters.

All standard rotary overburden casing is manufactured by Boart Longyear with a double-start cylindrical thread.
 

Conical Threads

Conical threads are similar in thread form and appearance to cylindrical threads except that there is a 0.5° - 1.0° angle in the thread form giving the thread ends a slight conical shape. It will require less turns to open and separate a conical thread joint due to its conical shape. Conical threads are available only on rotary-percussive casing.
 

Twin Drive Thread

Our patented TwinDrive™ threads have been developed for rotary-percussive casings and inner rods to handle the increased percussive power of hydraulic drifters. A typical cylindrical or conical thread form has a concentration of the clamping stresses at the base of the male thread. The TwinDrive™ thread form distributes the clamping load of the rod joint along the full length of the thread resulting in lower stresses at any given point in the thread. This means that it takes much less torque to make and break the rod joint and provides up to 40% additional tool life in hard ground conditions.

TwinDrive threads are available on all rotary percussive casing and rods. Boart Longyear uses the TwinDrive thread on all critical threading applications including modular flushing heads, TDN inner rod systems and non-percussive applications such as geothermal and jet grouting tools.