You might try using JB weld or a stripped hole repair kit from the local auto parts store (probably the same thing). Mix it up VERY well (like for 3 or 4 minutes), it takes a long time to set so don't worry about it hardening up quickly. If its a blind hole, use a thin wire to stir it in the hole and keep adding drips until they don't go in anymore. Wait a day or two and then accurately drill it and tap it. Don't tighten it too much, the compound will also act as a thread lock.