Broken bolt thread? You do not have to find an replacement one, you can just simply fix it with the Thread Restoring File. The thread file is a simple hardened steel four-sided bar with 8 different thread sizes cut into the body. The thread sizes are stamped on the sides for confirmation. It comes with 0.75, 1.00, 1.25, 1.50, 1.75, 2.00, 2.50, 3.00 threads.
How to use:
First step is to select the thread size, if you are not sure of the thread size, match up the bolt thread to one of the file sides. Some of the thread sizes may appear similar, so double-check with the file firmly engaged with the section of good threads placed in front of a bright light to highlight that the file is correct for the thread. If the file side is incorrect, light will show through the incorrect thread engagement.
Once you’re convinced that you have the correct side, gently stoke the threads just like doing a finish filing job on a piece of metal. Not too hard and not too soft. Don’t worry about cutting too deep or flattening the cylindrical bolt shape, the file limits the cut depth, sometimes the buggers are isolated deep nicks. Other times it’s a damaged section that’s been chaffed by another piece of metal.
Start with the good section of thread just next to the buggered part and start filing around the bolt toward the known bad section.
After one file pass, spritz some WD-40 and try the nut for smooth spin-on.
If it binds don’t force it — make another pass instead.
Do that until the nut spins on easily. Continue with the file and spin technique; notice that the bad section gets shorter leaving the worst section as the last to be finished.