Alton wrote:mjamero may have fin bolt inserts that were 1/4" 20 threads per inch and some one put metric bolts in or vice versa and it cross threaded the inserts. He could use a thread cutter (thread tapper) to gently recut the threads.
Re-threading was my first thought too. I own a Tap and Die set and tried. Unfortunately the inserts are too far gone. There is not enough material left inside to re-thread for bolts to bite.
The Drakes insert are M6 metric. Your point about the 1/4 bolts is likely correct. The board also came with another smaller fin that uses 1/4 bolts. I'm 99% sure 1/4 bolts were repeatedly used in the metric inserts.
So... now i need to find M6 x 12mm inserts or a dead donor fins that I can remove the inserts from.