Bicycle V Brake Pivot Pin, Bicycle V-brake pivot pin, V brake pivot pins, Cable Stopper, Cable Guide, Water bottle bush, Carrier bush, Water bottle Riveting bush Xingtai Yiming Bicycle Co., Ltd , https://www.ymbicycleparts.comTypes and Classifications of Drill Pipe Threads
When it comes to drill pipe, there are several categories based on the type of threads they possess. These include standard drill pipe, squared-tooth drill pipe, and weighted drill pipe. Standard drill pipe forms the core component of the drill string. Squared-tooth drill pipe connects to the top while linking to the drill collar at the bottom. Positioned at the uppermost part of the drill string, the squared-tooth drill pipe primarily serves to transmit torque and bear the weight of the entire drill string. The most common type is the square-tooth drill pipe. Weighted drill pipe acts as a transitional segment between standard drill pipe and drill collars. It effectively alleviates stress concentration in the transition zone where drill collars meet drill pipes, providing the necessary weight-on-bit (WOB) and reducing wear between the drill string and the wellbore walls.
As drilling technologies like roller cone drilling, air down-the-hole hammer drilling, and gas lift reverse circulation drilling become more widespread, API series downhole drill string components and tools are increasingly utilized. Notably, the API series threads connecting these components play a crucial role. Drill pipe joint threads can be categorized into four types based on their design: numeric (NC), internal flat (IF), full hole (FH), and regular (RGE).
Numeric (NC) threads are identified by numerical values representing the pitch diameter of the thread base in inches and tenths of an inch. All NC threads feature a V-0.038R flat-top and rounded-bottom triangular profile, with a rounded bottom radius of 0.038 inches (0.965mm). This type of thread is recommended by API and can be further divided into 1:6 and 1:4 tapers. They are commonly used in kelly drill pipes, drill pipes, drill collars, and stabilizers. NC50 threads are also employed in drill bits in the Daqing Oilfield.
Internal flat (IF) joints are designed to connect both external and internally thickened drill pipes, creating a diameter comparable to or slightly larger than the inner diameter of the drill pipe joint, the thickened pipe body, and the drill pipe itself. This setup ensures minimal drilling fluid resistance but results in a larger outer diameter that is prone to wear. All IF threads utilize a V-0.065 flat-top and flat-bottom triangular profile, with a flat bottom and a top width of 0.065 inches (1.651mm). While most IF threads are interchangeable with their corresponding NC threads due to identical structural dimensions (except for 5 1/2 IF), this design tends to cause stress concentration. As a result, API has discontinued certain IF threads, such as 4 1/2 IF and 4 IF, replacing them with NC50 and NC46 threads.
Full hole (FH) drill pipe joints are threaded to connect internal and external thickened drill pipes, ensuring the inner diameter of the drill pipe joint matches that of the thickened ends, albeit smaller than the inner diameter of the drill pipe itself. Although fewer specifications exist for FH threads, including V-0.065, V-0.050 (rounded bottom, 0.050-inch tooth crest width), and V-0.040 (rounded bottom, 0.040-inch tooth crest width), they have seen extensive use in faucets, square drill rods, drill rods, drill collars, and drill bits. Currently, only 5 1/2 FH and 6 5/8 FH threads, which employ V-0.050 profiles and 1:6 taper large-sized threads, remain in use. The remaining FH threads, such as 4 FH with a V-0.065 profile, have been replaced by the numeric thread NC40, akin to the internal flat thread.
Regular (RGE) drill pipe joint threads were originally designed to connect internally thickened drill pipes, creating a diameter where the inner diameter of the drill pipe joint is smaller than the thickened inner diameter, and the inner diameter of the thickened drill pipe end is smaller than the inner diameter of the pipe itself. The primary purpose of API’s regular threads was to apply them to drill bit connections. Since the drill bit is positioned at the end of the drill string, any stress concentration at the root of the thread is negligible. Consequently, API continues to support all RGE specifications. These threads utilize V-0.050 and V-0.040 tooth forms. In the 40th edition of API SPEC 7, two new sizes—1REG and 1 1/2 REG—were introduced, featuring a V-0.055 tooth form (flat bottom, 0.055-inch tooth crest width).
In the market, drill pipes vary depending on the manufacturer. For instance, Qianjiang Machinery produces drill pipes that are mainly categorized into twisted drill pipes, imitation British drill pipes, and ribbed drill pipes. Their threads and lengths are customized based on customer requirements. As drill pipe research and development progresses, the quality of drill pipes has significantly improved, leading to a reduction in prices. In the future, China’s drill pipe market will likely evolve toward a trend of technological advancement, efficient management, and enhanced quality.