"Don" wrote in message
k.net...


So, are you saying the metal, upon expansion, acts like the hole is not
there, that the whole thing is solid?
Incidently, I know that heating metal up, like pulleys, works because I've
done it.


It may clear it up if you think of a metal ring instead of a pulley. Cut the
metal ring and lay it out flat and heat it up. The length will change
considerably, although at the same proportion as the diameter. If the metal
rod was rolled back into a ring and heated you have the "length" expanding
and pushing against its self causing the hole to get larger. Although the
pulley will expand in all directions, the ring shape causes the hole to open
up when heated.
Confused yet?
Greg