This is for my own place, so perfect isn't needed.
We are refinishing an original hardwood floor from 1930. Most of it is oak, but the dining room is fir. The oak sanded down well enough, but the fir is either cupped, or was screwed up sometime in the past.
We used a vibrating square sander because I didn't want to mess it up more. We tried 36 grit and it took the high spots of poly off, so we switched to 20 grit to get the rest of it. Needless to say, it only started to do more damage to the high points and nothing to the low points, so we stopped.
What are my options. I have my RO 150, which with 120 grit seems to work, but I need to run it into the cup which makes it worse, but I could live with it if needed. Using the 20 grit by hand breaks it off, but takes forever and cuts the wood pretty harshly.
We are just going to put a clear satin over it.
I am in no way a floor guy, so I'll admit total ignorance in this situation. Unfortunately, I don't know a local floor guy to even ask, so here I am.