Aircraft Nuts - The castle nut, AN310, is used with drilled shank AN hex head bolts, clevis bolts, eyebolts, drilled head bolts, or studs. It is fairly rugged and can withstand large tensional loads. Slots (called castellations) in the nut are designed to accommodate a cotter pin or lock wire for safety.
The plain hex nut, AN315 and AN335 (fine and coarse thread), is of rugged construction. This makes it suitable for carrying large tensional loads. However, since it requires an auxiliary locking device such as a check nut or lockwasher, its use on aircraft structures is somewhat limited.
Aircraft Nuts
AN310 = aircraft castle nut. D = 2024-T aluminum alloy. 5 = 5/16 inch diameter. R = right-hand thread (usually 24 threads per inch). Every major Airline OEM today uses Marketing Masters' composite clip nuts and inserts in the manufacturing of their planes.
Aircraft Nuts
For many of these OEMs, Marketing Masters is their composite aircraft fastener standard. Marketing Masters works directly with the following OEMs in the installation of our aircraft fasteners: Aircraft nuts can be divided into two general groups: Non-self-locking and self-locking nuts.
Nonselflocking nuts are those that must be secured by external locking devices, such as cotter pins, safety wire, or locknuts. Self-locking nuts contain the locking feature as an integral part. Self-locking nut bases are made in a number of forms and materials for riveting and welding to aircraft structure or parts.
(See figure 6-10.) Certain applications require the installation of self-locking nuts in channels, an arrangement which allows the attachment of many nuts with only a few rivets. These channels are track-like bases with regularly spaced nuts which are either removable or non-removable.
The removable type carries a floating nut, which can be snapped in or out of the channel, thus making possible the easy removal of damaged nuts. Nuts such as the clinch-type and spline-type which depend on friction for their anchorage are not acceptable for use in aircraft structures.
Letters and digits following the part number indicate such items as material, size, threads per inch, and whether the thread is right or left hand. The letter "B" following the part number indicates the nut material to be brass;
a "D" indicates 2017-T aluminum alloy; a "DD" indicates 2024-T aluminum alloy; a "C" indicates stainless steel; and a dash in place of a letter indicates cadmium plated carbon steel. The code numbers for self-locking nuts end in three or four digit numbers.
The last two digits refer to threads per inch, and the one or two preceding digits stand for the nut size in 16ths of an inch. AN320 = aircraft castellated shear nut, cadmium plated carbon steel.
10 = 5/8 inch diameter, 18 threads per inch (this nut is usually right-hand thread). Aircraft nuts are made in a variety of shapes and sizes. They are made of cadmium plated carbon steel, stainless steel, or anodized 2024T aluminum alloy, and may be obtained with either right or left-hand threads.
No identifying marking or lettering appears on nuts. They can be identified only by the characteristic metallic luster or color of the aluminum, brass, or the insert when the nut is of the self-locking type. They can be further identified by their construction.
Do not install elastic stop nuts in places where the temperature is higher than 250° F, because the effectiveness of the self-locking action is reduced beyond this point. Self-locking nuts may be used on aircraft engines and accessories when their use is specified by the engine manufacturer.
As their name implies, self-locking nuts need no auxiliary means of safety but have a safety feature included as an integral part of their construction. Many types of self-locking nuts have been designed and their use has become quite widespread.
Common applications are: (1) Attachment of antifriction bearings and control pulleys; (2) Attachment of accessories, anchor nuts around inspection holes and small tank installation openings; and (3) Attachment of rocker box covers and exhaust stacks. Self-locking nuts are acceptable for use on certified aircraft subject to the restrictions of the manufacturer.
Self-locking nuts are used on aircraft to provide tight connections which will not shake loose under severe vibration. Do not use self-locking nuts at joints which subject either the nut or bolt to rotation. They may be used with antifriction bearings and control pulleys, provided the inner race of the bearing is clamped to the supporting structure by the nut and bolt.
Plates must be attached to the structure in a positive manner to eliminate rotation or misalignment when tightening the bolts or screws. The castellated shear nut, AN320, is designed for use with devices (such as drilled clevis bolts and threaded taper pins) which are normally subjected to shearing stress only.
Like the castle nut, it is castellated for safety. Note, however, that the nut is not as deep or as strong as the castle nut; also that the castellations are not as deep as those in the castle nut.
AN350 = aircraft wing nut. B = brass. 10 = number 10 bolt. 32 = threads per inch. Every major Commercial Airline today uses Marketing Masters' composite clip nuts and inserts in the maintenance of their planes.
By replacing metal fasteners with non-corrosive composite aircraft fasteners, it saves these airlines millions of dollars in the maintenance of their air fleet. Composite aircraft fasteners are also lighter than metal fasteners, which adds to their fuel savings.
Marketing Masters provides light weight, non-corrosive fasteners and clip nuts to the following airlines: Almost all elastic stop nuts are steel or aluminum alloy. However, such nuts are available in practically any kind of metal. Aluminum alloy elastic stop nuts are supplied with an anodized finish.
Steel nuts are cadmium plated. After the nut has been tightened, make sure the rounded or chamfered end of the bolts, studs, or screws extends at least the full round or chamfer through the nut. Flat end bolts, studs, or screws should extend at least 1/32 inch through the nut.
Bolts of 5/16 inch diameter and over with cotter pin holes may be used with self-locking nuts, but only if free from burrs around the holes. Bolts with damaged threads and rough ends are not acceptable.
Do not tap the fiber locking insert. The self-locking action of the elastic stop nut is the result of having the bolt threads impress themselves into the untapped fiber. Part numbers designate the type of nut.
The common types and their respective part numbers are: Plain, AN315 and AN335; castle AN310; plain check, AN316; light hex, AN340 and AN345; and castellated shear, AN320. The patented self-locking types are assigned part numbers ranging from MS20363 through MS20367.
The Boots, the Flexloc, the fiber locknut, the elastic stop nut, and the self-locking nut belong to this group. Part number AN350 is assigned to the wing nut. Numerous types of composite aircraft fasteners are used in the construction of a modern day airplane.
Even though they are small, aircraft fasteners are some of the most important materials that are installed in an aircraft. Commercial aerospace fasteners and clip nuts for airline OEMs effectively secure interior areas of an aircraft to appropriate standards that are determined by governing agencies.
Marketing Masters' composite clip nuts, press-fit inserts and potted-in inserts are ideal for the job, as they are non-corrosive, light weight, strong and less expensive than old titanium and stainless steel style fasteners. Contact us for more information regarding our advanced composite commercial aerospace fasteners, or call us at 425-454-5610 and we will gladly assist you with your direct clip nuts for airline OEM questions.
Marketing Masters is your trusted source for light weight, non-corrosive composite airplane fasteners. The light hex nut, AN340 and AN345 (fine and coarse thread), is a much lighter nut than the plain hex nut and must be locked by an auxiliary device.
It is used for miscellaneous light tension requirements. The Boots self-locking nut is of one piece, all metal construction, designed to hold tight in spite of severe vibration. Note in figure 6-7 that it has two sections and is essentially two nuts in one, a locking nut and a load carrying nut.
The two sections are connected with a spring which is an integral part of the nut. Boots self-locking nuts are made with three different spring styles and in various shapes and sizes. The wing type, which is the most common, ranges in size for No.
6 up to 1/4 inch, the Rol-top ranges from 1/4 inch to 1/6 inch, and the bellows type ranges in size from No. 8 up to 3/8 inch. Wing-type nuts are made of anodized aluminum alloy, cadmium plated carbon steel, or stainless steel.
The Rol-top nut is cadmium plated steel, and the bellows type is made of aluminum alloy only. Elastic Stop Nut Two commercial types of high strength internal or external wrenching nuts are available; they are the internal and external wrenching elastic stop nut and the Unbrako internal and external wrenching nut.
Both are of the self-locking type, are heat treated, and are capable of carrying high strength bolt tension loads. Thus, the spring, through the medium of the locking section, exerts a constant locking force on the bolt in the same direction as a force that would tighten the nut.
In this nut, the load carrying section has the thread strength of a standard nut of comparable size, while the locking section presses against the threads of the bolt and locks the nut firmly in position.
Only a wrench applied to the nut will loosen it. The nut can be removed and reused without impairing its efficiency. The digit (or two digits) following the dash or the material code letter is the dash number of the nut, and it indicates the size of the shank and threads per inch of the bolt on which the nut will fit.
The dash number corresponds to the first figure appearing in the part number coding of general purpose bolts. A dash and the number 3, for example, indicates that the nut will fit an AN3 bolt (10-32);
a dash and the number 4 means it will fit an AN4 bolt (1/4-28); a dash and the number 5, an AN5 bolt (5/16-24); and they are him. Sheet spring nuts, such as speed nuts, are used with standard and sheet metal self-tapping screws in nonstructural locations.
They find various uses in supporting line clamps, conduit clamps, electrical equipment, access doors, and the like, and are available in several types. Speed nuts are made from spring steel and are arched prior to tightening.
This arched spring lock prevents the screw from working loose. These nuts should be used only where originally used in the fabrication of the aircraft. The two general types of self-locking nuts currently in use are the all metal type and the fiber lock type.
For the sake of simplicity, only three typical kinds of self-locking nuts are considered in this handbook: The Boots self-locking and the stainless steel self-locking nuts, representing the all metal types; and the elastic stop nut, representing the fiber insert type.
Normally, elastic stop nuts can be used many times with complete safety and without detriment to their locking efficiency. When reusing elastic stop nuts, be sure the fiber has not lost its locking friction or become brittle.
If a nut can be turned with the fingers, replace it.
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