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In fastening, a nut is a simple mechanism to attach something together.
A nut is internally threaded, so it can be mated with another piece of hardware that is externally threaded, such as a bolt. Using rotation, it uses high clamping forces on the structure contained between the nut’s and bolt’s bearing surfaces. A nut is comprised of: a given thread size, a variety of material options and differing heat treatments. Nuts have an adequate wall thickness of 1.75 times the axial strength (tensile strength) of its mating bolt. The mating bolt is made from the same material and heat treatment, provided the effective thread length within the nut is equal to or greater than the major diameter of the bolt thread. Both pieces are ideal for bolt testing.
List of nut types:
Acorn (or Cap) Nut – a nut with a closed, rounded end to conceal mating threads for improved appearance, as a safety measure or to reduce thread oxidation at very high temperatures.
Anchor Nut (Fixed) – a cylindrical, non-wrenching nut, with integral ears by which it is either riveted or welded to the structure.
Anchor Nut (Floating) – a multi-piece nut assembly, usually consisting of a non-wrenching nut element, which is free to move radially within a cage or anchor plate, that is either riveted or welded to the structure.
Barrel Nut – describes a nut in which the thread is located in the center and it is perpendicular to the axis of a barrel-shaped piece of material. This type of nut is used to secure forgings and castings or to attach other structural members to forgings. The barrel nut is retained in the forging or casting by holes that are drilled perpendicular to the bolt axis. The complete assembly is T-shaped.
The barrel nut is also known as a Cross Dowel Nut that is often used in ‘knock-down’ furniture applications.
Blind Anchor Nut – a blind rivet which doubles as an anchor nut. It is normally a one-piece hollow internally threaded rivet. The threaded section (or tail) of the rivet is engaged with a stud, which exerts pulling force toward the rivet head which is itself restrained by an anvil. The net effect is the upsetting of the center section of the nut, forming a blind internal threaded member which can be used in understructures.
The blind anchor nut is also known as a Rivet Nut or Threaded Insert. The internal threads of Blind Anchor Nuts/Rivet Nuts/Threaded Inserts can be mated with an externally threaded member as is typical of nuts or can be strictly used as a means to rivet.
Captive Nut – a nut, usually with a splined grip, designed to be pressed into an undersized hole in the understructure. Works like a blind anchor nut once installed, but it must be installed from the blind side of the work.
Clinch Nut – a captive nut that is installed in a similar fashion, except that a portion of the captive nut protrudes through the understructure on installation and is flared over.
Castle Nut – a nut, not normally self-locking, but having four or more transverse slots laterally in its tail section, is designed to anchor a cotter pin or lockwire. Castle nuts are used to secure bearings, crank pins and other hinged members.
Jam Nut – a low-height, free-spinning nut used as a locking device by running it down the externally threaded member and jamming it against the tail section of a previously installed primary nut.
Spline Nut – a self-broaching captive nut used in limited access areas.
Wrenchable Nut – configuration consists of either hexagon (six sides), twelve point or twelve spline. Wrenchable nuts are also identified as shear or tension nuts. Shear nuts are low height with minimal bearing area. Tension nuts are significantly taller with a large bearing area at the base. Nuts may have a captive washer on the base to prevent brinelling of soft structure during installation. Nuts may also be designed as self-aligning to compensate for surface angularity. Here the nut base has a spherical radius which mates with a concave radius in the washer. Most aerospace wrenchable nuts are self-locking.
Did You Know? Nuts
Some of the most stressed out parts of a high-dollar
performance engine are the relatively inexpensive
nuts and bolts that hold it all together.
Disclaimer: The views expressed herein are provided for informational purposes only and do not constitute professional advice on any subject matter. Spaenaur does not accept any responsibility for any loss which may arise from reliance on information contained herein.
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