Individual lengths of drill pipe are connected to each other with threaded rotary shouldered connections called tool joints (Figure 1.0). Four types of tool joints (or thread forms) are used commonly used.
API tool joints. Tool joints with specifications defined by theAPI include all NC connections, 5 1 2 FH, 6 5 8 FH, and API regular. connections. Detailed information on the dimensional properties of these tool joints can be found in API Spec 7 and Section B of the IADC Drilling Manual.
FIGURE 1.0 Tool Joint Nomenclature.
Single shoulder non-API tool joints. For tool joints similar to (and sometimes interchangeable with) API tool joints, detailed information on the dimensional properties can be found in Section B of the IADC Drilling Manual. Examples of non-API tool joints are extra hole (EH or XH), open hole (OH), and many others. Table 2.9 shows the interchangability of single shoulder tool joints with API tool joints.
Double shoulder tool joints. Double-shoulder tool joints have a shoulder on the nose of the pin that contacts an internal shoulder in the box. These additional shoulders limit the amount of axial deformation in the pin and provide more torsional strength.
Other proprietary threads. There are other tool joints that do not fall into the previous categories.