"Richard Cline" wrote in message
...
In article ,
"Greg O" wrote:

"Don" wrote in message
k.net...
Won't expanding the pulley make the hole smaller?



Nope, when you heat a ring shape, such as a pulley, the hole will get
larger.
Greg


Is that because the air in the hole expands more than the metal and
forces it to be bigger?

I wonder what scientific property allows one portion of the metal to expand
(the outside surface of the pulley) while the other part contracts (the
hole).