From my experience the finer the grit the more likely you are to heat the old finish to the point that it melts and gums up the paper quickly. Try a grit much coarser than 320 to remove the old paint - more like 36 to 80 - then follow up with finer grits to condition the bare wood to the surface you want to repaint. Frequent use of a gum rubber sandpaper cleaner stick will also help remove the old finish that sticks to the paper as you go. You will quickly find a combination of grit size, sander speed, feed speed and down force that will remove the old finish quickly without doing too much damage to the wood. Every different old finish I have had to remove restoring this 100 year old building has behaved differently. Latex over an old oil finish is the hardest to take off as the latex wants to gum up badly before the old oil junk gets removed. The result is a bubble gum like junk that is a PITA. But, after enough experimenting I did find a combination that worked well. In that case I used the RAS on low speed, very light down force and coarse grit to rip off most of the latex and then progressed through the old oil junk with the RO and finer grits to get to the bare wood. Just before refinishing I used the Viles pads to scour the surface and scuff it just enough to take the new finish well.
Jerry
