Damage to the internal threaded part in the holes occurs as a result of overtightening or the use of an “off-thread” bolt. Its restoration can be done in various ways.
- - epoxy adhesive;
- - tap;
- - threading oil;
- - threaded screw cap;
- - core.
Select methods of thread restoration depending on the operating conditions of the structures. You can restore it using epoxy glue.
Fill the hole with epoxy glue and wait for a while until it hardens slightly. Screw in the bolt and wait until the polymer is completely dry. It is necessary to know that this method of thread restoration is not suitable for parts subject to high loads and vibrations, as well as when assemblies and structures are operating at high temperatures.
Alternatively, first re-drill the damaged hole with a heavy-duty HSS drill. Tap the threads to the correct size using a special threading oil.
Lubricate the cutting edges of the tool with oil during the cutting process with force, rinse the tap in kerosene and reapply oil to its edges. With this method of restoring the thread, the hole will be larger.
If it is impossible to increase the diameter of the hole, restore its thread using a screwdriver. It is a hollow cylindrical device that has a threaded inside and outside of the required size and pitch.
Drill the hole with a drill. Select a tap that matches the outer diameter of the screwdriver and cut the threads. Install a screwdriver into the hole. Cut off its protruding top, if necessary. Punch a notch at the border of the new thread and the screwdriver so that it does not twist out of the hole.
If possible, weld the damaged hole using welding. Then drill a new one in the same place - of the required diameter. Thread it with a tap. This recovery method is considered the most reliable. You can also make a new hole next to the old one if the design of the part allows.