Be careful with the liquid nitrogen. Some metals can experience structural changes such as embrittlement or stress fractures from the use of liquid nitrogen. Low carbon steel can even be damaged by dry ice. I have succesfully used Dry ice for things like cylinder sleeves and bearing cups. Haven't heard of anyone sleeving brake drums for years and that was only on trucks and buses to get a different material for the lining to work in stop and go traffic. I suppose it becomes cost effective if no drums are available. [Non-text portions of this message have been removed]