Ed, Oak grain is very hard to get perfectly flat unless you fill the grain with wood filler. I use a product called Wood-Kote to fill open grain wood like Oak and Walnut. Yes you would have to take it down to bare wood again to fill it. You will not harm the wood by taking the urethane off. Since you didn't stain it that eliminates one possible problem. Can you post a closeup photo of your bed wood? It might be easier to take your boards to a woodworking shop and have them plane the urethane off. Some shops have large belt sanders also. You could get them to sand the boards for you. I have used this process to flatten out table tops that I have built. I have used my planer to take the urethane off my original pine boards. Some shops will not run urethane boards thru their planers because it will dull or chip the blades, which is an added expense to them. Unless you do not like the raised areas of the oak grain there is not much else you can do. If you feel that the boards look great as is, just leave them that way. that would be a natural oak finish. I have built many cabinets out of Oak and didn't fill the grain. It is more of a natural finish. If you have any more question that I can help you with please ask. Frank
