Stainless steel aviation

ntroduction to Basic Knowledge of Stainless Steel Aerospace Parts Processing for Aerospace Parts
We know that aerospace equipment requires a lot of components, among which fasteners are indispensable components. Without fasteners, thousands of aircraft components cannot be combined together. Today, we will briefly introduce the basic knowledge of fasteners for stainless steel aviation parts processing.
1、 Thread type
There are many standards for threads, among which:
1. Coarse and fine threads of the same size and number, if the threads are the same, the nominal diameter of the threads is the same, but the number of threads per inch of length is different.
2. The distribution of tolerances varies, and the specific specifications for threads with a diameter of 1 inch vary. For example, NF specifies the use of 14 teeth per inch, which is generally represented by 1-14NF. UNF specifies the use of 12 teeth per inch, which is represented by 1-12UNF.
2、 Coordination level
There are different grades of threads, and these different grades indicate the degree of fit and tightness that threads should have.
Generally speaking, it has five levels, with level 1 indicating a loose fit. When in use, the nut can be easily tightened by hand. Level 2 represents free fit and is suitable for aviation screws. Level 3 represents moderate fit, and most aviation bolts need to reach this level. 4. Level 5 belongs to tight fit and requires the use of specialized tools. The higher the level, the tighter the tightness of the threaded pair fit.
3、 Identification symbols
The bolt diameter, length, and material parameters of fasteners with general identification, where the measurement unit for diameter is 1/16 inch, and the measurement unit for bolt rod length of the machine body is 1/8 inch; The manufacturing material of bolts is generally identified using English letters or symbols, with "C" indicating that the material used is stainless steel; "DD" indicates that the material used is 2024 aluminum alloy; "-" indicates that the material used is nickel alloy steel.
3、 Nut
There are also many types of nuts used in aerospace. Below are several commonly used nuts:
1. Standard aviation nuts
For example, the AN310 groove top nut is usually matched with AN3-AN2O body bolts, and its thread standard is NF (fine thread). Nickel alloy steel, stainless steel, and 2024 aluminum alloy materials can all be used to produce this type of nut.
2. Self-locking nut
There are several conventional models of low-temperature self-locking nuts, such as AN365 and AN364. When locking, insert an elastic ring into the thread, with an inner diameter slightly smaller than the thread. Rotate the nut to allow the bolt to pass through the bottom thread, and when it needs to enter the top thread, the resistance of the elastic ring should be overcome so that the bolt thread and nut can coordinate and mesh. When using such fasteners on airplanes, there are requirements and limitations, and they should be used according to the requirements.
4、 Washers
The main function of washers in aerospace fasteners is to make the force under the nut or bolt head more uniform, adjust the distance between the thread and the surface of the component, and also play a role in locking, anti loosening, and pre tightening indication. The commonly used high end washers include AN960 ordinary washer, AN935 open end elastic washer, AN936B external tooth elastic washer, and so on.