Teach you to read the head markings of aviation fasteners

Fasteners can be called standard parts, which means that they conform to a set of systems that have been established in the industry, so that it is convenient to provide uniform and consistent fastener products for all customers. We are familiar with automobiles, wind power, special equipment and other fields have their own standards, but it seems that there are more standards in the field of aviation fasteners than in other fields.

Speaking of which standards define aviation fasteners, we will first narrow the scope of discussion to fastener standards formulated by standards organizations or governments that can be reached worldwide. Therefore, we will tighten those aviation fasteners. Firmware manufacturers and aircraft manufacturers’ corporate standards are excluded.

In the field of aviation manufacturing, NAS is the most influential standard for imperial fasteners, which can cover both commercial aircraft and military aircraft.

NASM

It is also an imperial fastener, originally used as a military standard, but then transferred to the NASC (National Aerospace Standards Committee) for management in order to obtain continuous maintenance and development, so it can be understood as the military standard in NAS (NASforMilitary) .

NA/NAM

NA is a metric product corresponding to the NAS standard. NAM is a metric product corresponding to NASM.

In addition, there are many US government standards that are also very common in the aviation manufacturing field, such as MS and AN. Have we seen some standards at the beginning of MIL? These are also U.S. military standards, but these are usually used to define more detailed technologies. For example, MIL-STD-100G is used to define drawing specifications, and MIL-STD-1312 is used. To define the test method of coating thickness and so on. (Guide: Common loosening problems of threaded fasteners, anti-loose measures, anti-loose structure)

After you have the above standard knowledge, the next step is to understand the specific meaning of each character in the part number. Unfortunately, it seems that every standard has its own special definition mode, so it is not possible to use a certain standard definition mode to penetrate other standards.

For example, some standards use the same part number plus different diameter codes to indicate different diameter sizes, but some standards use different part numbers to indicate different diameter sizes.

For external threaded fasteners, in addition to the diameter size, there are codes for various lengths in the part number. Under normal circumstances, you will find a dash in the fastener part number, and the code after the dash is the length code.

Standard number, diameter size, length, these most basic information can be obtained from the part number. Sometimes, some codes that characterize the special properties of the part are mixed into the part number, such as material, self-locking characteristics, surface treatment, groove hole type, etc.

NAS6208-10, in this type of part number, the strength, material, surface treatment and other information are fixed, and the only change is the length code behind the dash. NAS6208 represents a bolt with a nominal diameter of 1/2, a tensile strength of 160KSI, and a hexagonal head alloy steel plated with cadmium. The only variable is code 10, which means the length of the bolt is 5/8.

Through the above introduction, can you quickly get the basic information of a part from the head mark of the fastener? Is it possible to put the following scattered parts back to the correct position based on the information such as the head markings?

I hope that the simple introduction can be helpful for identifying the part number of aviation fasteners. For every worker in aviation manufacturing, whether it is technical selection, procurement quotation, installation and quality inspection, identification of parts Number is one of the most basic tasks. Although the skills in this area can be improved by studying the standards, it is still better to approach and practice through the old-fashioned methods. The more time invested in this area, the greater the gain.

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