Our house was built 22 years ago, we've been here 10 years now. Recently it became evident that we needed to replace the fixtures in one of the bathrooms. All went well until I got to the drain. When I tried to unscrew it, I ended up breaking the crossbars at the bottom of the drain. So now it looks like I'll have to cut it out. The question is what is the best way to do that? The unit simply won't budge, every time I grab a corner with vise-grips, the corner simply comes off. So, off it comes, but I really don't want to damage the tub any more than it is (some of the fiberglass has already chipped off, I'll have to see about finding a refinishing kit when I'm done with the drain).

I see recommendations to cut out drains in this forum quite a bit, but no suggestions on what tools or how to actually do that.