I am not quite sure what you are trying to do, but starting with an orbital sander was probably not the right place to start.

If you are thinking of "refinishing," then there are many ways to remove the old finish. Sanding is probably the worst. It is inefficient, does not do a good job removing the old finish, and is risky in terms of veneer sand-through. If you can at all swing it, I suggest using a chemical stripper in a well-ventilated area. It's messy, but does the best job, knows when to stop (something sandpaper does not) and gives you a good starting point.

Second, practically no production furniture has "polyurethane" on it. It is simply not a production finish as it takes too long to apply, takes too long to dry, and is not agreeable to repair & touch up. It is a much better probability that it is a type of lacquer. This is good because you can do over lacquer with more lacquer and it will blend in with itself. There is a small chance that it's a conversion or two-part finish that will not take a top coat of any type well and won't strip well, either.

If you just wanted a "freshening up" of a lacquer finish, all you needed was to do a good cleaning, a light hand scuff-sanding and apply a couple of fresh coats of lacquer (Watco and Deft are two brands available at most places).

Thanks very much for responding!

Well, I didn't wait -- I went ahead and sanded the top because it had some raised places as well as deep scratches. I got away with it pretty well, I think. I did a Minwax stain on it a couple of hours ago and it looks great. Not 100% perfect as there are still a couple of faint scratches, but I don't dare sand deeper so they get to stay and we'll call them "character." It does look tons better than it did and almost brand new. I'm eager to get it finished because it's in my way where it is. I'm not keeping it; it's a gift for someone else.

Tomorrow I will do a Tung Oil on it, I think, to give it back its gloss. Or is that wrong? That's what they sold me in the store. I figured Polyurethane was a wrong thing to use.

I do agree with you that stripping is better if there is a choice, but in this case I had to sand. I figured if I had to, I could always paint the piece. I love the shape of it.

If your can says, "Tung Oil Finish" it is probably not tung oil; it is not even part tung oil. Most of these are either thinned varnish or thinned varnish with linseed oil mixed. Not that there is anything wrong with these, they are just not what you think. They would properly be called "wiping varnish" or oil-varnish mix (sold under Danish Oil, Antique Oil, -Oil, etc.

Real tung oil will say something like 100% Tung Oil and will NOT say "contains petroleum distillates" It would not be my choice for a table and certainly not over top of an existing finish.

Thanks, Bob! That's very good to know. You are very knowledgeable and I really appreciate your advice. I'll have to double-check what I have now. It was the only one my hardware store had -- Homer Formbys.

If I remember right, Formby's is a Alkyd resin/Soya oil varnish, thinned to wiping consistency.

Here is a link that might be useful: Tung oil finishes and other lies.

Thanks for the article. I read it but I'm tired, so maybe that's the reason I'm still a bit confused. I have some other furniture here that is looking a bit dry and un-shiny. I've been applying the Formby's Tung Oil (which is a wiping varnish according to your article) and it's looking much better. This should last longer than the Old English Scratch Coat, right? That's what I've used in the past and it looks great at first and then fades away.

So would I be better off to get a lacquer to apply to things to make the shine last longer and protect the wood better? Or a brush-on varnish? Or just polyurethane it? What about if it's an antique?

Thanks!