What You Should Know About Aerospace Fasteners?
The role of aerospace fasteners is to connect thousands of components of the aircraft to form a whole, Transferring load in component diameter and coordinating deformation during loading.
What Are The Standards For Aerospace Fasteners
NAS
In the field of aviation manufacturing, NAS is the most influential standard for British fasteners. It can not only cover commercial aircraft, but also cover military aircraft.
NASM
It is also a British -made fastener. It was originally used as a military standard, but then transferred to NASC which is the abbreviation of “National Aerospace Standards Community” for managing to obtain continuous maintenance and development. So it can be understood as the military standard in NAS.
NA / NAM
NA is a public product corresponding to NAS standards. NAM is a public product corresponding to NASM.
In addition, many US government standards are also very common in the aerospace industry , such as MS and AN. MIL is also US military standards, but it is usually used to define some more detailed technologies.
Aerospace Nuts
Standard Aerospace Nuts
AN310 Castle Nut
Application: It is used in conjunction with AN3 ～ An2O bolt
Thread: NF (fine pitch thread)
Materials: Nickel alloy steel, stainless steel and 2024 aluminum alloy
Mark Symbol: ” -“, “C” and “D”
For example, Mark : AN3L0 C 6
It can be expressed as the slotted top nuts used in combination with AN6 bolts made of stainless steel
AN320
Name: Shear Castlenut
Application: There is only the part with shear stress, which is used in conjunction with the AN2L ~ An36 shaft pin bolt.
Materials: The same as the AN310 nut, but the thickness of the nut is slightly thinner.
For example, Mark : 320D6
It is expressed as the hexagon slotted flat nut used with AN26 axle pin bolt, made of 2024 aluminum alloy.
AN315
Name: Ordinary nut
Application: It is used for parts subject to large tension. Its disadvantage is that it must be used with a anti -loose nut or a spring washer to ensure its fastestness.
Material: It is the same as AN310 nut.
Thread: There are two types of right-hand threads and left -hand threads.
For example, Mark: AN315-7R
Represents The right-hand thread nuts are equipped with AN7 bolts, made of Nickel alloy steel.
AN316
Name: Lock nut
Features: This is a hexagonal lock nut adopting double nuts to prevent loose measures. It is used on an AN315 ordinary nut to prevent ordinary nuts from loosening.
Self Locking Nuts
Low -temperature self -locking nut
Model: AN365, AN364
Working principle: Low-temperature self -locking nut inserts an elastic ring in the thread and the thread that matches the inner diameter ratio is slightly smaller. When the nut is rotated to make the bolt go through the bottom thread and enter the top thread, the resistance of the elastic ring must be overcome to make the bolt thread and the nut top thread engage harmoniously. After all bolts are tightened, the elastic ring section forces the top section thread to tightly bite the bolt thread to prevent loosening.
High–temperature self-locking nut
Model: AN363
Both self -locking nuts are swollen after tightening, and they are locked by elasticity. They can be repeated use multiple times. Because their manufacturing process is relatively simple, the application of these two self -locking nuts on airplanes is becoming more and more wide.
Low -temperature self -locking nut
Model: AN365, AN364
Working principle: Low-temperature self -locking nut inserts an elastic ring in the thread and the thread that matches the inner diameter ratio is slightly smaller. When the nut is rotated to make the bolt go through the bottom thread and enter the top thread, the resistance of the elastic ring must be overcome to make the bolt thread and the nut top thread engage harmoniously. After all bolts are tightened, the elastic ring section forces the top section thread to tightly bite the bolt thread to prevent loosening.
High–temperature self-locking nut
Model: AN363
Both self -locking nuts are swollen after tightening, and they are locked by elasticity. They can be repeated use multiple times. Because their manufacturing process is relatively simple, the application of these two self -locking nuts on airplanes is becoming more and more wide.
Aerospace Washers
AN960 is the most commonly used standard aerospace washers,
Application: It is widely used under the hexagonal nut.
Materials: carbon, steel, brass, stainless steel and aluminum alloy.
AN936 washer has uniform elasticity, good anti -loose effect.
Aerospace Screw
Aerospace screw is applied to non structural connection, fairing and removable panel which are non main stressed structures
Features
(1) The screw shank is generally full threaded, and the thread is manufactured according to level 2 free fit accuracy.
(2) There are two types of flat and pointed tails.
(3) During installation, the screws are generally twisted in the screw holes on the component, and usually turn the screws for tightening purposes.
Categories Of Aerospace Screw
1. Mechanical screw
Mechanical screws are commonly used on non -constructors, assembly of aluminum castings parts, such as light, small parts and gear box cover plate on the airplane.
Features:
The screw rod is a fully threaded
There are two types of threads, including coarse tooth and fine tooth
Materials: low -carbon steel, stainless steel, brass and aluminum alloy, etc.
Common models
(1)AN500 is coarse round head screw and AN501 is fine round head screw
(2) AN505 is coarse tooth 82 ° countersunk screw and AN507 is fine tooth 82 ° countersunk screw
(3) AN515 is coarse round head screw and AN526 is fine round head screw
2. Structural screw
Material: Made of alloy steel
Features:
(1) The stretching and shear strength is the same as the AN type bolt of the same size and material
(2) This type screw has the same length of the same size bolt
(3) The screw rod has polished rod section which means no thread and the fitting accuracy of the screw is the same as that of the AN type hexagon head bolt, so it can be used as a structural bolt
Types of screw head
Round head, flat round head, 100 ° countersunk head, etc
Common models
(1) AN509 100 ° flat screw
(2) AN525 washer head screw, this screw has a large head similar to the pad, with a large loading area.
(3) AN502 and AN503 round head screw
AN502 is a fine teeth round head screw, and AN503 is coarse tooth round head screw. The round head of the screws has a slot and a small hole through the fuse.
3. Self-tapping screw
1. Mechanical screw
Mechanical screws are commonly used on non -constructors, assembly of aluminum castings parts, such as light, small parts and gear box cover plate on the airplane.
Features:
The screw rod is a fully threaded
There are two types of threads, including coarse tooth and fine tooth
Materials: low -carbon steel, stainless steel, brass and aluminum alloy, etc.
Common models
(1)AN500 is coarse round head screw and AN501 is fine round head screw
(2) AN505 is coarse tooth 82 ° countersunk screw and AN507 is fine tooth 82 ° countersunk screw
(3) AN515 is coarse round head screw and AN526 is fine round head screw
2. Structural screw
Material: Made of alloy steel
Features:
(1) The stretching and shear strength is the same as the AN type bolt of the same size and material
(2) This type screw has the same length of the same size bolt
(3) The screw rod has polished rod section which means no thread and the fitting accuracy of the screw is the same as that of the AN type hexagon head bolt, so it can be used as a structural bolt
Types of screw head
Round head, flat round head, 100 ° countersunk head, etc
Common models
(1) AN509 100 ° flat screw
(2) AN525 washer head screw, this screw has a large head similar to the pad, with a large loading area.
(3) AN502 and AN503 round head screw
AN502 is a fine teeth round head screw, and AN503 is coarse tooth round head screw. The round head of the screws has a slot and a small hole through the fuse.
3. Self-tapping screw
Features
(1) It is fastened by tapping itself in the assembly hole.
2) The screw head type: Flat round head, 100 ° countersunk head, large flat round head.
Common models
(1) AN504 and AN506 are often used to install removable parts such as labels.
(2) AN530 and AN531 are self-tapping screws used for metal plates. AN530 has a flat -round head and AN531 is a countersunk tapping screw.
Mark: AN501B -416-7
Represents:
416: diameter 4/16 inches,
7: The length of 7/16 inches
B: indicating the material is brass
AN: Air, Navy standard
501: Grooved cylindrical head, fine thread
Summary
This article mainly introduces some basic knowledge about aerospace fasteners, which includes the standards and types of nuts, washers and screws used in the aviation manufacturing industry.
