Hi, I'm trying to figure out the ideal TPI for a large (4" nominal) cast iron pipe. As I understand it 18 and above if for thin metal, 6 and below is for wood. There are combined 10/14 TPI blades - would this be the best choice? Or would a single 8 TPI or 10 TPI be better? I don't need a smooth cut, I just need to cut through the bastard as fast as possible before my weak sawzall battery dies :laughing: Thanks for any advice!