I was thinking of refinishing my 50's era cork floor tiles, but I couldn't find much first-hand info about it, so I'm posting my story here so the next guy will have more to go on.
First of all, you can only refinish old school solid cork. My tiles are about 3/8 inches thick. The new engineered stuff has a very thin veneer of cork that doesn't have enough meat to be sanded.
I called a couple flooring guys in the phone book; one said he'd do it for $3 a square foot, the other said that cork can't be refinished because it's too soft.
I always like a challenge, so I was off to the rental yard.
There are three types of flooring sanders generally available: drum, random orbital and square pad. Get the square pad because it's the least aggressive.
I started with 60 grit pads, they lasted about 100 square feet each before they were gummed up with the old polyurethane. After finishing the room with the 60s, I switched to 120s and that was all that was necessary, I now had a very nice smooth finish on a newly exposed, virgin layer of cork.
The vacuuming was tedious. Since the tiles have a beveled edge, you really have to get on your hands and knees with a powerful shop vac to get all the dust out of the "grout lines" between the tiles.
I went with a water based finish system because it's less toxic, and this rec room only gets sock-footed traffic so I didn't need the more durable oil based poly. I used a fuzzy applicator pad on the end of a broomstick to apply. After a coat of sealer, and four coats of the water based urethane, she was looking good.
For a medium-sized den (300 square feet), it took two days of labor, $40 for the machine rental, and $200 for the materials (sandpaper, urethane and applicators).
I was surprised at how easy it was to get good results and I don't understand why some pros would claim that it can't be done.