Hello all,
first thanks for all the help this board has provided so far. We we recently bought a home built in 1983. The home has 3/4'' oak planks throughout. It is not nessessary in bad shape but definaly has been neglected. Not much of any finish to speak of.
So we are using obital palm sanders with 150 grit and sanding the floors. They seem to be smooth enough after this and it is easily removing what little finish there was.
However, there are very small gaps (maybe pencil lead thickness) between all the planks. Im not sure if the gaps are supposed to be there or if it was an original moisture install problem. Either way it does not look bad or bother us. My concern tho is that once we apply our surface coat will more coat fill in the gaps and look darker than the surface of the planks? It would be a rediculuus amount of work to use a wood filler for all the gaps. Please advise.
Also Im not sure if we need a sealer or if we can just go right to the eurathane surface coat. Not planning on any stain. Please any and all advice is apprecaited!

You can live with the gaps if you wish. Or trowel fill them and sand off the filler. Many pros would fill because it would look better and would encapsulate any contaminents that may exist down in those gaps. No need to use a separate sealer IF you are using a oil-modified polyurethane. Most other floor finishes do require that you use their sealer.