Destroyer
God
I have seen those before. My dad always had a few in his toolbox but I never knew what they were. I'm going to get info on the threads and order one. Worth a shot.
I was a machinist for a number of years before I became a plant engineer. They work, and they work well. Saved many an item by using them. Just take your time, let the file do the work. Just lay the teeth into the groves and then work the file straight forward and back. Be careful to not work the file in an arc or a circle on the threads. Easy Peasy Lemon Squeezy .