A U-bolt is a bolt in the shape of the

letter U U or u, is the twenty-first and sixth-to-last letter and fifth vowel letter of the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ''u'' (pr ...

with

screw thread A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a ...

s on both ends. U-bolts have primarily been used to support

pipework Within industry, piping is a system of pipes used to convey fluids (liquids and gases) from one location to another. The engineering discipline of piping design studies the efficient transport of fluid. Industrial process piping (and accompan ...

, pipes through which fluids and gasses pass. As such, U-bolts were measured using pipe-work engineering speak. A U-bolt would be described by the size of pipe it was supporting. U-bolts are also used to hold ropes together. For example, a 40 Nominal Bore U-bolt would be asked for by pipe work engineers, and only they would know what that meant. In reality, the 40 nominal bore part bears little resemblance to the size and dimensions of the U-bolt. The nominal bore of a pipe is actually a measurement of the inside diameter of the pipe. Engineers are interested in this because they design a pipe by the amount of fluid / gas it can transport. As U-bolts are now being used by a much wider audience to clamp any kind of tubing / round bar, then a more convenient measurement system needs to be used. Four elements uniquely define any U-bolt: # Material type (for example: bright zinc-plated mild steel) # Thread dimensions (for example: M12 * 50 mm) # Inside diameter (for example: 50 mm - the distance between the legs) # Inside height (for example: 120 mm)

References

Threaded fasteners {{Material-stub