Excited Flyboy,

My discussion was hypothetical. I did not mean to imply that cylinders and rings were made of the same material, though I am sure it has been done at some time in the past.

I know about fitting parts with interference fits, however there are other purposes, such as the interference fit at the top of an ABC piston and sleeve.

As far as the thermal coefficients of cast iron and steel, I suggest that you look at the linked chart, they are indeed different. Not only that they absorb heat at a different rate.

http://www.engineeringtoolbox.com/th...ls-24_859.html