Threaded inserts have different names in different countries, but their applications are similar and include the following
- Thread repair
- Increase thread strength
- Conversion thread specification
In aviation applications, the most common and common wire thread insert is made of diamond shaped stainless steel or bronze coils that are wound and locked by outward expansion force when screwed into the threaded hole to achieve a higher strength threaded connection. This type of thread insert is very common in thread repair applications and can provide stronger threads for softer metals, such as aluminum alloys, which cannot be achieved by tapping directly into the aluminum alloy plate.
There are many kinds of thread insert, compared with the spiral type thread insert, if it is mechanically locked, it can significantly improve the pull and torsion resistance of the thread insert, such as the following:
In the face of such a wide variety of thread insert products, which one meets your application requirements? Usually, we will start with the material of the mother board, and then consider the influence of the operating temperature, the requirements of the load, the existence of the vibration load, and the requirements of the tool, that is, the installation.
Here are some other considerations I'd like to share:
- Distance from the edge of the motherboard
This distance refers to the distance from the center of the installation hole to the nearest edge of the mother plate, in principle, this distance should not be less than the diameter of the thread insert, for the thread insert of brittle materials, during the installation process will produce a large stress, this time should consider increasing the edge distance appropriately.
- Material hardness
The material referred to here is the material of the mother board, that is, the material of the plate that needs to be installed with the thread insert. Some thread insert locking method is through the use of key connection, if the hardness of the mother board is high, when installing the thread insert, I am afraid that the external force can not be the connection key into the parent material, which needs to be completed in advance when making holes in order to connect the key in place.
- Selection of surface treatment of thread insert
We all know that in high temperature applications, the surface of the silver plating is a common solution, so it is commonly used in aviation engine applications, mainly to reduce the wear of thread bite in high temperature applications, play a role in lubrication. However, when the mother plate material is titanium alloy material, special attention is needed, because the combination of silver and titanium may cause stress corrosion problems.
- Installation impact
One of the main reasons for the failure of the wire thread insert is the improper initial installation. Therefore, choosing the appropriate tool and the correct method is an effective way to extend the service life of the thread insert.
The selection of any fastener product often needs to involve many factors. In the past, whenever similar application problems were encountered, the first thing that came to mind was strength, size, installation, and now it has begun to pay more attention to cost and maintenance issues. Excellent product selection is inseparable from every process of manufacturing.