Join Date: Nov 2003
Location: SE Minnesota
Bikes: are better than yours.
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In a previous life I fixed light industrial machinery for a living. (Now I fix buggy software.) Helicoils are really not that hard to do. You get a kit for the size bolt you need to fit. It comes with coils, a drill bit, a coil inserter and a tap. You drill the current hole with the bit, then tap it with the tap. Next, you wind the coil on the insertion tool and slowly turn it into the hole. The coil stays in as you then wind the insertion tool back out. The inside of the coil serves as a perfect set of new threads. Oh yeah, use plenty of oil in the process.
Still, before doing a helicoil I'd try to retap it with a tap. Tap and die kits can be had at home improvement stores but metric sizes are harder to find and you may be better off looking for an industrial supplier. Even individual taps can be had. A tap is basically a cutting tool that cleans up the threads of an existing threaded hole or creates new ones by simply screwing it in. A tap designed for the size hole you need to fix needn't be expensive.
If you don't have enough material to support the coil and maintain the strength of the braze-on, you may need to go down a size in the rack mount bolt. Of course, that might not be as strong.
If all this looks scary to you, see if you can find a local machine shop that can help you. You're looking for a guy who can do one-offs and prototypes, not a big CNC production operation. Maybe even an auto repair place will help you find someone since they usually know someone who can turn brake rotors. Maybe even a guy who customizes motorcycles can do it.