Once more, the digest lag has ensured I can't offer much more to maTeo's question about pedal hole thread repair other than this. ( I have used the helicoil set mentioned on by another poster many times and with 100% success) here is another spin on it's usage, since some members seem unfamiliar with this "retap and insert" system:
I have made several tandem cranksets (which in the "crossover" mode required right hand arms threaded left and vice-versa) by using the helicoils to accomplish this reversal. Just be careful when using the oversize tap to go the "wrong" direction on the arm. My old taps have a nice reamer portion to start with, so it isn't too hard to do. I agree with the suggestion to start from the backside in all situations dealing with cleaning up/rethreading crank arms. I saw a tandem crankset on ebay a long while ago which was made this way; I wondered if it was one I had made along time ago.
Hey, M! where's my saddle, boy?