Cannot figure out how to Random Orbit Sand (I must be stupid)

[Dan Friedrichs]

Trying to improve my sanding technique...

Festool Rotex 5", with a new pad, a new piece of Granat P120 paper, Festool dust extractor...

Piece of walnut, fresh from the planer (which has sharp knives and leaves a nice surface, to being with)

Set the sander to ROS mode (not rotary mode), turn the vacuum suction way down, lightly place the sander on the work, let the weight of the sander do the work (no pressing down). For this board, which is ~6"x8", I spend maybe 30 seconds sanding, until there is a uniform scratch pattern all over.

Wipe some BLO on, and there are little spiral marks visible.

I just don't get it. For the last several projects, I've taken to hand sanding with P120 paper after the ROS, because at least then, I can get rid of the spiral marks, but it's a HUGE amount of work. It's almost less work to NOT use the ROS, and just hand sand everything!

What am I doing wrong?

[Grant Aldridge]

I'm not familiar with that brand of paper but it sounds like you just need a finer grit. I like to use a 180 or 220

[Lee Schierer]

120 grit paper should not be you final grit before finishing. You need to go to at least 220 and maybe to 320. Even so, in some woods you will see the swirl marks even from a ROS. For a piece that small, you could easily hand sand it going with the grain to eliminate the marks.

[Robert LaPlaca]

120 is not a fine enough for a oil finish, keep going till 220.. the oil is basically magnifying the swirl marks..

[Matt Day]

It’s the sander. My Bosch doesn’t do that, but since I really want you to succeed, i’ll trade sanders with you.

[Dave Cav]

Pretty much what everyone else said. You're stopping too soon. For my normal furniture work I go to at least 220, for table tops and other large flat surfaces, 320 or higher. Lately I have been making a bunch of natural finish door and window trim and I take it to 180.

[Brian Henderson]

120 grit is not nearly enough, I never stop before 220 and often go higher, depending on the wood and/or the project. In fact, 120 is often where I START sanding, assuming the wood is generally well-prepared before that.

[Marc Rochkind]

I agree with what everyone else said (especially Matt). My understanding is that the initial coarse grade is to remove machine marks, and it sounds like you don't have any. If the surface is as perfect as you say it is, you might start with something even finer than 120.

But definitely, as everyone else says, end up with something 180 or higher, depending on what finish you're applying. Probably the walnut won't be stained, so maybe finer than 180.

[Prashun Patel]

In fact, you may find that even with a good sander like your Rotex, you have sanding swirls at 180 or 220. I like to go higher to 400 or 600. By then the scratches get quite small to see.

Many people recommend sanding by hand lightly with the final grit to remove those scratches. I will do that when I want to be extra sure.

[Leo Graywacz]

If you are oiling wood you need to sand much higher. 600-800 grit. 320 is about the minimum you should stop at.

[ernest dubois]

But lets face it, it is the sander. Finer grit just means smaller tears, small enough that they are no longer so irritating to look at granted but even at that scale they leave their effect and you end up with... an orbital sanded surface.

[Mike Cutler]

I gotta agree with the others Dan, 120 is too soon to stop for a "softer" wood like walnut.
I have four DeWalt Orbitals set up as follows; 150,220,320,400 and above, grit.
Festool has an instructional video for using their sanders. It might be worth a look.

https://www.youtube.com/watch?v=rZZyypf-Qqk

[Dan Friedrichs]

But lets face it, it is the sander. Finer grit just means smaller tears, small enough that they are no longer so irritating to look at granted but even at that scale they leave their effect and you end up with... an orbital sanded surface.

I think this is it. From 5' away, the surface looks fine - I'm getting picky, and I guess that means this is the problem.

I prepped another test board, and did sections where I stopped at 100, 120, 150, 180, 220, and a section where I hand sanded at 120. It's obvious that the swirls just get less noticeable as grits progress, but are still visible.

Though, if I'm topcoating with a film-forming finish, it seems silly to sand the wood to 220+ just to avoid swirl marks, doesn't it? Seems like it makes more sense to use the ROS to get most of the machine marks gone, then hand sand at ~120 grit in the direction of the grain?

[Dan Friedrichs]

I gotta agree with the others Dan, 120 is too soon to stop for a "softer" wood like walnut.
I have four DeWalt Orbitals set up as follows; 150,220,320,400 and above, grit.
Festool has an instructional video for using their sanders. It might be worth a look.

https://www.youtube.com/watch?v=rZZyypf-Qqk

Mike, this was SUPER useful!

For those of you who have Rotex sanders: do you leave them in Rotary mode all the time (like is done is this video)? I was under the impression that rotary mode was for rough use, and the ROS mode was for "finishing" use (>120 grit-ish) - is that incorrect?

[Bob Varney]

Dan,

I use my rotex for the lower grits, my rotex has a 5mm swirl, then use my its 150 with a 3mm swirl. For a really smooth surface.

Bob

[Bill Dufour]

I try to never use brand new paper on a finished project. Put it on the sander then a few seconds on a back side or scrap to knock off any high spots of grit then onto the project. When you are talking about several thousand pieces of grit what are the possibilities that at least one ended up clumped on top of another and glued there. It only needs to be 1/1000 of an inch higher to be visible.
Note that your swirl marks are not evenly spaced and all over. They are separate small single individual swirls caused by one individual grit randomly spaced. They may even be loose grits that shifted and re embedded in the paper. Or I suppose small shavings of wood like a planer may mark the surface with if dust collection is poor.
Bill D.

[Jim Becker]

Aside from the comments already stated, check your pad on your sander to make sure there's not a spec of dirt on it between the pad and the abrasive disk. ;) It happens...

Also, Rotex isn't a "one hand" tool like the regular Festool ROS so you need to keep that in mind so it stays balanced. Rotex is designed to err toward the rotary motion and heavy stock removal and that's a two-handed process for control. ROS mode is a bonus, but the balance of the tool still prefers both hands, um...handling it.

[Dan Friedrichs]

Also, Rotex isn't a "one hand" tool like the regular Festool ROS so you need to keep that in mind so it stays balanced. Rotex is designed to err toward the rotary motion and heavy stock removal and that's a two-handed process for control. ROS mode is a bonus, but the balance of the tool still prefers both hands, um...handling it.

I have noticed that :)

Jim, I think you have a Rotex? Do you keep it in rotary mode all the time, or do you find the ROS mode useful in any way?

I tried prepping a sample board using only rotary mode from 80, 100, 120, 150, 180, 220, and there's still some swirls visible. I ordered some 380 and 400 to see if that makes them disappear, though.

[Jeff Ramsey]

Here's an alternative approach. I typically reach for my LN 85 scraping plane (or a Stanley 85) in lieu of coarse/fine sandpaper, with several grain-raising sessions. Then I leave my Festool ROS and Vac in the corner, and with 400 grit and a block I finish up (and only stop at 400 if it's a satisfactory finish, which it often is). Less noise and great results.

https://www.lie-nielsen.com/product/scraping-planes/cabinet-makers-scraper?node=4075

[Jason Lester]

I have noticed that :)

Jim, I think you have a Rotex? Do you keep it in rotary mode all the time, or do you find the ROS mode useful in any way?

I tried prepping a sample board using only rotary mode from 80, 100, 120, 150, 180, 220, and there's still some swirls visible. I ordered some 380 and 400 to see if that makes them disappear, though.

I don't have a Rotex but I'm pretty sure you'll need to switch it to ROS to get a smooth surface with no visible swirls. Rotary is used for stock removal and quick cutting. ROSS is for a uniform scratch pattern that will disappear under the finish.

[Phil Mueller]

In a word, no. Pretty much any finish is going to accentuate scratches, dents, and other flaws. With penetrating finishes, I usually wet sand up to 800 grit. With film forming finishes, I sand to at least 320. I typically follow up a ROS with a quick hand sanding. And even then, I wipe the whole thing down with DNA looking for anything I’ve missed. A finish is only as good as the prep.

[mreza Salav]

I do minimum 180 (typically 220 grit). Hand sanding with the grain is needed IMO if you want to truly get rid of the ROS marks. No matter what good of a sand paper you have I think a light hand sand with the grain and with the same final grit of ROS helps a lot.

[Alan Lightstone]

I put 120 grit on my Rotex, and place it gently down on the workbench. Then I put 120 grit on my 150/3, and do all my sanding with that, up to 220.

The Rotex is a beast in my hands. Exhausting and way too much vibration. I basically never use mine. On the other hand, I use the 150/3 on virtually all projects.

Not sure this helps you at all, but it's my experience.

[roger wiegand]

Another possibility:if you started at a coarser grit (or sandpaper with a few bigger particles) you may not have gotten the deeper sanding marks out as you went from 80, say to 120. Those swirls will then persist, even if you go to 1200 grit. It's critical to completely eliminate the sanding marks from the prior grit before moving on, let they be permanently enshrined in your final project. (You can, of course, sand them out with a finer grit, but it takes forever.)

[Jim Becker]

I have noticed that :)

Jim, I think you have a Rotex? Do you keep it in rotary mode all the time, or do you find the ROS mode useful in any way?

I tried prepping a sample board using only rotary mode from 80, 100, 120, 150, 180, 220, and there's still some swirls visible. I ordered some 380 and 400 to see if that makes them disappear, though.
I do have a Rotex, but it's the larger 150. I rarely use it in "ROS" mode because my primary sander 98% of the time is my 150/3. I did use it for my recent "kitchen continent" project to "level" the top as it was too big for anyone's wide-belt. (I should have kept it in two sections for that) I really don't understand why you're getting so much swirling. Any time I've had that problem, it was the result of debris under the disc or a piece of some kind of grit getting caught on the business side of the disc.

[John K Jordan]

...
Wipe some BLO on, and there are little spiral marks visible.
...

I didn't take time to read all the posts so this may be covered. I do several things when sanding. (Most of my use is with small pneumatic random orbital sanders on woodturning - usually with a Grex.)

One, I sand by hand after each of the coarser grits with the same grit and take out any cross scratches, sanding with the grain with a soft backing pad. My theory is that if I can't get a 320 scratch out with 320 paper it will be very difficult or impossible to get it out with 400 or 600. Hand sanding after every grit also eliminates the unpleasant discovery of scratches from a much coarser grit. If I see any of those, I'll drop back and re-sand with the coarser grits. I don't find the hand sanding tedious if done at each step. Maybe it's a zen thing.

Two, intermediate scratches are far easier to see with a good glancing light AND after wiping on a liquid. I use naptha for this since it dries so quickly. A sopping wet surface will let me see what the figure and color will look like after applying oil, but as the wet gloss evaporates (or after wiping with a slightly damp cloth) is the perfect time to look at the surface from different angles with the glancing light. Scratches that are invisible on the dry wood will be quite obvious.

I use small diameter light sources instead of broad, diffuse sources like indirect lighting or long fluorescents high overhead. A bright hand-held light works well. The glancing angle puts the scratch in a dark valley, made even darker with the liquid.

Also, it may have been mentioned but the quality of the sandpaper can make a big difference. Some cheap paper is poorly graded and may contain a few particles of coarser grit. Nothing worse than a few coarse scratches in a 400 grit sanded surface. Don't forget to carefully clean the surface before each grit to remove any stray particles that may have broken off the coarser paper. I used compressed air followed by wiping with a damp cloth. (I used to grind and polish metal samples in a metallography lab and I have experience with what a single stray particle of grit can do!)

BTW, this may not apply to your work but with most woodturnings I rarely start with coarser than 320 or perhaps 220 grit because I usually remove tool marks with hand scrapers first. Also, with walnut and other open-grain wood, if I'm finishing with oil I usually wet sand with the oil at the coarser grits to help fill in the pores. On large, flat surfaces a grain filler would probably be easier and a quicker.

JKJ

[Ole Anderson]

I typically use 120/220 to remove planer marks and other imperfections, but then I don't use an oil finish either. On bigger projects I use my 5" PC angle grinder style of ROS with the dust vacuum kit added. I found it jumped around a lot when holding the disc flat so I tended to hold the disc at an angle and use the edge. When I went to the vac kit, I got a 6" disc for it and now it sits flat and doesn't jump around. Go figure... I believe the 5" PC has a smaller orbit than the 6" so it is less aggressive and you get a finer finish. Sorry this a bit off topic, but it may be useful to someone.

[Dan Friedrichs]

Very useful, Ole. So you stop at 220?

[Ole Anderson]

Very useful, Ole. So you stop at 220? My discs stop at 220. Lately that seems all I need. Lately I have worked with oak, hickory and aromatic cedar. I typically finish with four wiped on coats of P&L 38 satin mixed 50/50 with naptha. I never see any swirl marks. I hit the dist nibs lightly with a 400 grit block sand by hand only after the last coat.

[Dan Friedrichs]

Thank you all for the replies. I think I've figured it out!

I was previously annoyed by the slowness of ROS mode on the Rotex. Turns out, you don't need to use the slow mode if you don't want to :) Using only rotary mode, I went from 80-100-120-150-180-220-320 and the final board had only slightly visible swirls. I should say, the swirls were still very obvious at 180 and 220 - it was going to 320 that was really quite key.

I think I could safely finish at that point, but a very quick hand sand at 320 really eliminated any last vestige of a swirl mark.

I'll try omitting a few of the intermediate grits (150, 220) in the future.

Thanks, guys! I used to HATE sanding (mostly because the amount of hand sanding I was doing was an extreme amount of labor, and because it never felt like I was sure the sander was "doing" anything), but now I'm just so tickled at how well this works that I don't mind it.

[Ed Labadie]

I have an older RO150, it's my primiary sander.

Rotex mode is for hogging with coarse grits.

Random orbit mode 95% of the time. Usually go 100, 150 finish with 220. I never press on the sander, just guide it.

Usually 2 passes with each grit, speed dial set on 4 1/2.

Swirl marks are non-existant.

Ed

[Leo Graywacz]

5mm is rather large for a finish sander too. I use the Mirka Ceros and it also has a 5mm orbit. But I have none of the problems you seem to be having. But I've been sanding for 30 years. And just like painting, everyone thinks they can do it, and they can. But everyone can't do it well.

[Bob Cooper]

I have the rotex and the smaller non rotex festool sander and the ROS mode of the Rotex is different. The patterns are different — it’s a good bit bigger on the rotex. So I don’t use the rotex for final finish sanding. I use it almost exclusively in aggressive mode