One of these: https://www.cncrouterparts.com/pro48...kit-p-251.html ? Did Avid tell you that this machine would mill cast iron? What non-ferrous metals did they say it would work on? I'd be skeptical of its ability to mill aluminum well, let alone anything harder, especially with the extended Z axis. Did you buy this primarily for working with metals, or did you mostly plan on cutting wood or plastics?