Hi Michael, Instead of using a grinder for the cutting of the drain, you may want to consider using a reciprocating saw, or sawzall, as some may know it.
It's essentially a large jig saw, shaped to look like a rifle, and it uses larger blades than a jig saw. A reciprocating saw is very versatile, and can be used for other such projects where one needs to cut a particular line where one isn't present. If anything, it's a good excuse to buy a new tool. Smile. Victor Gouveia
