On another thread, a couple of turners whose work and experience I admire suggested that with wood one shouldn't wet sand, shouldn't wet sand with oil, or should only wet sand at the higher grits. I disagree with all those positions. Where possible, I wet sand. The only exception is where I don't want to use oil on the wood (to preserve its color or because I don't want oil under the final finish). So, I thought I'd share my thoughts on the pros and cons of wet sanding with oil. (I generally use walnut oil, but I've also used BLO.)
1 - Wet sanding is faster. Even with the extra time it takes to set up (I place newspaper over the bed of the lathe and pour some oil into a container that I dip my sandpaper into), wet sanding takes me less time than it takes me to dry sand.
2 - It does a better job. The finish from any given grit of sandpaper is finer when I wet sand than when I don't.
3 - It keeps the dust down. When wet sanding, I don't bother to run the dust collector or to put on my respirator. When dry sanding, I use both.
4 - It's quiet. Primarily because the dust collector is off. But, it's even quieter than dry sanding without the dust collector on. Virtually the only sound is the humming of the lathe.
5 - My sandpaper lasts longer. One turner suggested that wet sanding clogs the sandpaper. I've found the opposite to be true. Yes, a 'sludge' of oil, wood dust, and grit, will build up on the paper, but it's easily floats away with a little more oil. The oil keeps the sandpaper cleaner, allowing it to cut cleanly for a longer period of time. Contrast that with dry sanding wood that has pitch in it.
6 - No heat checking. I ruined one of the first pieces I turned from an exotic (ebony) because I got it too hot while sanding. That's not happened when wet sanding -- even though I keep the speed up on the lathe.
7 - No need to finish! For most of my utility items, my final finish is walnut oil. By the time I've sanded through the grits with walnut oil as my lubricant, I'm done. I've already applied 5 or 6 coats of oil, so there's no need to apply more oil once the sanding is completed.
1 - It's messy. The spinning of the lathe throws off excess oil. The floor behind my lathe, the ceiling, and my turning smocks are all stained with oil that's been thrown off while I'm wet sanding. Of course, if I turned the speed down on my lathe, that wouldn't be as much of a problem. I forget and many smaller items are sanded at 2,000+ rpm.
2 - It's more expensive. At least I think it is. I certainly use more paper towels. (I wipe off the object between grits. If I were dry sanding, I'd just blow off the item with compressed air.) I also use more walnut oil than I otherwise would. But, since it's my preferred finish, it's not a lot of extra oil. Offsetting these additional costs, is a reduction in sandpaper use. I can sand 4 or 5 pens or bottle stoppers without needing to change paper. I cannot do that dry sanding. (I throw away paper when I'm done for the day. So, if I only turn one item, unless it's large, there isn't any sand paper savings.)
What are your thoughts?
Here is a link to a video from Doctor's Woodshop on using walnut oil as a lubricant. My method is slightly different than his, but I think he does a good job of explaining the process. Robo also has a video, but I couldn't find it.