[masraum]

Originally Posted by drcoastline

I have done my fair share of floors as well. 1990C4S has pretty well answered your question. I will just reirerate it is imperative to to keep the sander moving so you do not dig in. I would also say if you haven't done ths before don't be to agressive with the grit. Start with 80 max and see what happens and get used to the sander.

This statement has me worried based on the cup in those boards. Removing an 1/8" is going to leave you really thin on the top edge of the groove. You are going to run the risk of splitting the top of the groove off. Where the finished floor meets they grey floor that was under the tile is there a lip? The finished floor should be lower from wear and refinishing. Can you gauge how much wood has been removed?

Don't hesitate to buy a used belt sander off FB.

Good call. There is no lip where I've already pulled up the walls, and there's a TON of grain showing on the wood, that I suspect is 100 years old. When I had a closer look, I see that someone hit the floor with a belt sander, but only took off peaks, and maybe let the thing sit so there are a few troughs. Using a straight edge and feeler gauges, I found that most of the troughs are less than 0.010". I found one (the one in the red box) that is .025", so less than 1/32". Who knows, maybe I won't have to take off 1/8". In places that I was able to measure, most of the flooring seems to be closer to .85" than .75"