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Taper threads, British Standard Pipe Taper thread (BSPT), whose diameter increases or decreases along the length of the thread; denoted by the letter R. BSPT threads [2] These can be combined into two types of joints: Jointing threads These are pipe threads where pressure-tightness is made through the mating of two threads together.
Such an appropriately sized drill is called a tap drill for that size of thread, because it is a correct drill to be followed by the tap. Many thread sizes have several possible tap drills, because they yield threads of varying thread depth between 50% and 100%. Usually thread depths of 60% to 75% are desired. People frequently use a chart such ...
The seal provided by a threaded pipe joint depends upon multiple factors: the labyrinth seal created by the threads; a positive seal between the threads created by thread deformation when they are tightened to the proper torque; and sometimes on the presence of a sealing coating, such as thread seal tape or a liquid or paste pipe sealant such ...
A screw thread is an inclined plane wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread. More screw threads are produced each year than any other machine element. [1] Threads are generally produced according to one of the many standards of thread systems.
The across-flats definition is the common standard today, and has been for many decades. The larger spanner in this photo is from the 1920s or earlier. Its face was polished to allow the size stamp to show well in the photograph. This example is American, but it illustrates the way that spanners for Whitworth fasteners were typically labelled.
Jointing threads: These are pipe threads for joints made pressure-tight by the mating of the threads. They always use a taper external thread, but can have either parallel or taper internal threads. This means a male BSPT (tapered) fitting will seal happily onto a female BSPP (parallel).
One aspect of this method of sizing is that the size increment between drill bits becomes larger as bit sizes get smaller: 100% for the step from 1/64 to 1/32, but a much smaller percentage between 1 47/64 and 1 3/4. Drill bit sizes are written as irreducible fractions. So, instead of 78/64 inch, or 1 14/64 inch, the size is noted as 1 7/32 inch.
In oil field tubing, buttress thread is a pipe thread form designed to provide a tight hydraulic seal. The thread form is similar to that of Acme thread [10] but there are two distinct threaded portions of differing diameters and profiles, the larger having a wedging profile, with a tapered sealing portion in between the larger and smaller diameters.