Will 120 grit close the grain and make the finish blotchy?

Q: I have recovered douglas fir floors from carpet and linoleum, scraping the mastic off with a diamabrush/buffer. So far so good. My sanding plan is to use the buffer machine and 60/80/100/120 discs. Then finish sand with an oscillator at 120 to get out the large swirl marks. Do you think this will ‘close the grain’ so the oil finish will be blotchy?

Maybe use of a drum sander is more typical, but I’d have to drive a way to rent it, and I already own the buffer and its sanding plate.  

A: It’s a coin toss.  If the floor is flat from one board to the next, if you can remove whatever is on the wood as far as any adhesive and finishes down to bare wood, you could be ok.  I wouldn’t go to 120.  I’d stop at a 100 grit screen.  You could use paper discs initially as they are more aggressive then use a 100 grit screen for the final.  I’d run a random orbital or orbital sander on the edges, finishing with 80 grit.  Douglas Fir is nice to stain and finish.  I hope it wasn’t finished with shellac.  That could present an issue with heating and smearing.

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