How to repair a broken thread

Sometimes the internal threads of nuts or bolt holes become damaged, usually from overtightening. Thread stripping is a very common occurrence, especially when working with aluminum parts, because aluminum is so soft that it can be easily stripped. Overstretched spark plugs are another common cause of thread failure.

Usually, the external or internal threads are only partially stripped. After cleaning it with a tap or lerka, it continues to work. Sometimes, however, the thread is seriously damaged. If this happens, then you have two options to choose from:

1. Drill the next appropriate larger hole, thread it, and install the larger bolt, screw, or stud.



2. Drill a hole and thread it to fit the plug, then drill the plug and thread it to the original size. You can also buy a plug already pre-threaded to the original size. Then you just need to drill a hole to the desired size, and then install a threaded plug into this hole with a bolt and locknut. When the plug is fully seated, unscrew the lock nut and bolt.

Regardless of which method you use, work calmly and carefully. A little impatience or carelessness during one of these relatively simple procedures can ruin a day's work and cost you dearly if you damage an expensive part.