The heat on the outside will cause the metal to expand. It isn't a mind
reader. It can make the ID smaller. However cold on the outside will
shrink it, causing the ID to increase (you would have to agree to that,
right?). This is a school kids science experiment. When you see it work
with heat, it just losend it probably because of differential heating
and its affects and is erroniously attributed to the outside piece's ID
getting bigger, but didn't. So heat and cold does losen things, just not
like a lot of people think.

It doesn't work quite like that. As another mind experiment, consider heating
a solid disc of metal. The only point that doesn't expand is the very center
point. Any other point on the disc outside of the center moves away from the
center.

Now, consider a metal doughnut. Heat it up the same way as the solid disc.
Every point on the doughnut will still move away from the center of rotation.
The entire ring gets bigger.

Earle Rich
Mont Vernon, NH