If the threads on the stud are stripped, follow the post from nkfro. If your problem is that the hex faces on the nut got rounded off, here's what I've done in the past, although it was on the nuts on a B23 crank pulley.

The proper size wrench is 10mm. Try a 6-point socket if one is available. Usually they are hard to find. Then try a 5/16 inch socket. Put it on an extension, leave off the ratchet handle. Turn the socket until it seems to want to grip, then hit the end of the entension with a hammer, not a lot but enough to get the socket on the nut a little. Then slip the ratchet handle on and try - keeping things very perpendicular.

You might also put so PB'Laster loosener stuff on the nut and let it soak several hours.

I have had no luck with Vise Grips on such a problem as in order to grip the rounded nut the grips have to be so tight that the nut is distorted into a stop nut and holds the stud even tighter.

Good Luck,

Bob

:>)

It would be more common for the stud to be stripped than for the nut itself to be stripped. Applying a prying pressure from beneath the nut while turning it will allow the nut to catch undamaged threads if possible. If not, then a hacksaw blade with 32 teeth per inch (TPI) can be laid against the stud and cut the nut off in a vertical cut. The problems will be keeping the nut from turning and keeping damage to the threads to a minimum. The former can be done using pliers or even an open end wrench. Thread damage kept to 5 - 10 degrees of the stud circumfrence will make installation of the new nut a bit tighter but will not significantly weaken the stud, particularly in this application.
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