"Leo Lichtman" wrote in message
...

"Jeff Wisnia" wrote: I was tought that it's the differential expansion
across the bolt/block interface which cracks the rust.
^^^^^^^^^^^^^
It is true that differential expansion could either make the bolt tighter
or
looser, depending on the distribution of heat, but I don't think that is
what's working here. Hot rust is simply not as tough as cold rust. I
would
heat the whole area, but concentrate the flame mainly on the bolt head.
That is the easiest place to apply the heat, which will then be conducted
down the bolt to the threads. If you tried to heat the "block" without
heating the bolt, I think you would have a hard time keeping the flame off
the bolt anyway. And, after you have applied enough heat to do some good,
conduction will probably result in a fairly even temperature distribution
across the thread interface.

The main object is to get it hot enough to weaken the bond, without
getting
the steel so hot that you weaken it.



Get it nice and hot, then spray the crap out of it with WD40 ( Shut off you
torch first )

The rapid cooling and vaporization will draw the gaseous form of the
lubricant into the interface on contraction and break the oxide into
smaller, dislodged particles.

I keep wondering if he is dealing with a left hand thread, thus complicating
the issue for him.

--

SVL