I'm no plumber so I won't give you any plumbing advise but I will tell
you this. Are you using a grinding wheel ( you know knid of looks like a
round stone about 1/2 " thick) Becuse if you are you will be there for
the next milenium. What you need is a cut off wheel ( round disk about
1/16" or so thick) this will act more like a saw blade and take a hell
of alot less time to cut through the pipe.