If you can get behind the handhold with a hacksaw, I think that they make some "grit" blades that should cut the bolt.We use hardened steel hex bolts, hardness C38-45, shaft diameter 3/8, head diameter 9/16, head length 3/8, to fasten large and expensive climbing holds to a plywood wall, with a nut behind the wall. Some nuts cannot be reached, the bolt sticks in the nut, and the nut may spin behind the wall. Rather than sacrifice the holds that are stuck, we would like to remove the head of the bolt, so the hold may simply slide off the bolt shaft (the bolt is a bit recessed into a roughly 10/16 hole in the climbing hold). We tried a 9/16 carbide extraction bit, but 15 minutes of drilling only removed at most half the head. Is there a better method? A cutting wheel with aluminum oxide quickly cuts the bolts (albeit with many sparks), but for large holds a cutting wheel cannot reach behind the hold to cut the shaft. Is there a burr or drill bit with aluminum oxide (or any other equipment) that we could use to buzz off the head, by inserting the device into the opening in the hold containing the bolt? I'm not sure this is the correct forum for this query, so let me know if it should be posted elsewhere.