I have a bolt with a nut on it that holds a small wheel onto a fork. I assume I over-tightened because now the nuts turns while I hold the bolt, but it will neither tighten or loosen. Also, it's on so tight, that I can't fit a saw blade between the nut and the fork.
Any suggestions on how to easily remove this without damaging the wheel? (though I'm willing to destroy the bolt.)
You can use a special tool called a nut-splitter.
Another method is to use a rotary tool (e.g. Dremel) with a cutting wheel or grinding bit. There's a strong likelihood of damaging the bolt.
As a last resort you can use a smaller angle-grinder to cut through the nut and/or bolt. There's a good chance of damaging the fork (or yourself) unless you are very carefull.
You haven't said how much of the bolt is sticking out, but there is another non-destructive method you can try if there is enough exposed bolt
Take two additional nuts and thread them onto the bolt, but not all the way to the stuck nut. Then, tighten these nuts against one another quite well (i.e. turn the outermost nut CW onto the bolt while at the same time trying to turn the innermost nut CCW). Then, take a box or crescent wrench to the outermost nut and hold that nut stationary while trying to loosen the stuck nut with another wrench. Trying to turn the stuck nut will also try to turn the bolt counterclockwise. Since you are holding the outermost nut stationary, any CCW motion of the bolt will act to tighten that nut against the nut next to it. Since it is already tight, holding the outermost nut stationary ought to also hold the bolt stationary. You may need to tighten the nuts against one another quite a lot to keep them from moving relative the bolt.
