Friends, I have been making fine furniture for years as a hobbiest and still am not sure about the final grit that I should be using?
I have read quite a few articles to guide me. Most recommend up to 220 grit. But, I am willing to go up to 320 and beyond if it would make for a nicer smooth surface ready for painting. If you could inform me of what final grit you recommend and why, pls do. Additionally, if you could refer me to any authoritative articles, please do. I believe that Bob Flexner recommends up to 220 grit. But in this month’s Fine Woodworking magazine, issue 277, on page 53, Christian Becksvoort writes: “finer grits with the orbital sander… unfortunately he does not specify what the “finer grits are”. Your thoughts and recommendations would be most appreciated.
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For a painted finish, 220 is more than good enough.
320 is nice 400 if you want exceptional.
The short answer is, it depends. It depends on the hardness of the wood you are using and it depends on the finish you will apply. If you will be painting the piece, some remaining fine scratches won't matter much. If you will be using a clear finish, you will need to progress through finer grits until all the fine scratches from the previous grit are gone. You can test this by wiping the surface with mineral spirits. If that doesn't expose any scratches, you are probably good to go with your finish. I have found that, if hand sanding with the grain, I can usually stop with 180 grit on hardwoods like oak, maple, or cherry. I might go to 220 with poplar or pine but, I don't usually put clear finishes on those.
One other situation is if you are going to stain it. Any stain you put on the piece will accentuate any scratches even more than mineral spirits. So, in this case, you may want to go one more step in the sanding grit just for insurance. However, keep in mind that many stains will tend to look lighter on wood that is sanded to a finer grit. So, some balance may be required. Testing on scrap is always good.
If you are using an ROS, it is probably good to go one step finer than you might go by hand because some of the ROS motion is cross grain. I can't see the need to go beyond 220 grit on wood. With some exceptions, I think the finer grits are for smoothing and polishing finishes.
I second the point about wood stain - I just stained some wormy maple and it picked up every single small scratch from an orbital sander which I had used at 220. I ended up using the OS to 220, then hand sanded using 150, 180 then 220 which worked fine and gives a great surface for oil finish.
You are faced with a couple of things here; visual appearance of the surface after the abrasive and tactile feel of the surface. Many folks stop at 150 or 220 and the finish they use adds color(s) and / or films the surface giving an acceptable visual and tactile result. Remembering that sanding is scratching the surface to a finer and finer degree, if your finish will hide the current scratch pattern and will create a thick enough film to feel smooth, you're in.
I use a lot of penetrating oil finishes so I sand to a higher grit. This is a balancing act since I use minimal or better yet, no colorants. The finer sanded areas will absorb at a different rate than the coarser areas so I am taking this into account as I do my surface prep.
I’ll add that it depends on what wood you’re using. White oak, maple and alder are fine with 220 grit, but sapele needs more attention. Sometimes I’ll take those even farther, but never beyond 400 grit. I haven’t used a lot of red oak, but it’s fairly porous and open-grained, so I would ponder sanding it to a much higher grit (400).
For those woods 400 would always be my routine finish grit. But even then, you may need to use a sanding filler (most of them are some shellac-based compound). You can go with pumice for an even finer finish, but I have no experience with that.
If you’re painting, well I have no experience painting the furniture I make either, but paint hides a multitude of sins, as it were. I’ve painted furniture that was previously built and painted, and just scuffing the previous coat is fine.
I'm building an oak bassinet right now, just started staining two days ago. I took it down to 400 and it felt and looked great but I wasn't as pleased with the stain results. Worked it back up to 320 and it's looking great. Excluding whatever you do in the finishing after that, I would say 320 is more than enough.
I echo ChipSawdust's comments regarding wood type here. The grain is obviously important to consider. I still can't see anything REALLY benefiting from a grit finer than 320 for stains, and especially for painting.
I'm working with red oak right now.
I'm using 220 to round over corners slightly. And I definitely go up to 400 on all surfaces. The difference is like day and night. I usually also sand or wet sand with 400 for a nice surface after shellac or Waterlox goes on. Usually after every coat. Just a quick swipe to break raised fibers and dust. 400 feels like butter, were 220 just isn't good enough for me.
There's always fine steel wool. And for the final finish I recommend you try Alan Noel's article on wet sanding. It's found in Highland Woodworking's library section. The result is amazing. It's sloppy but fun.
You have everything you need to answer his question yourself. You don’t need Becksvoort or Flexner’s opinion. Just sand some test boards to different grits, apply the finish as usual and see if you can notice any worthwhile difference among the boards.
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