How to fix a stripped oil drain plug?
Sometimes threads of drain plugs, also referred to as fill plugs or pipe plugs, or their mating parts can become stripped out from excessive use or accidental cross‑threading.
When working with a stripped drain plug, begin by removing it from the mating component and inspecting the plug's threads. If the threads are beyond repair, replace the plug with a new one. If the threads are only partially damaged, they can be corrected using a die with the same thread dimensions as the plug. Simply thread the plug into the die while applying a lubricating oil to the threads of the plug. Thread the plug completely into the die and back to correct the damaged threads.
Next, inspect the threads of the mating component. If the damage to the threads is minimal, a tap of the appropriate size can be threaded into the mating component to correct the damaged threads. If the threads are damaged beyond repair, the mating component may need to be repaired by installing a helical thread insert. When performing the procedure, metal shavings will likely enter the pipe or container being serviced. Make sure to clean out all shavings prior to putting equipment back in service.
Make sure to refer to your engineers' specifications when repairing critical components as some repair methods may not be suitable for all applications.