I want to start a thread (and hopefully, a discussion) about sanding, and orbital sanders in particular. I think this is the right place as I am interested in it as relates to finishing wood projects and surfaces.

I have always been taught to sand with the grain. It did not take much experimenting to have the wisdom of this demonstrated. Those cross grain scratches are hard to remove. So, I sand with the grain, by hand or with a belt sander.

Every now and then I want to sand a large flat area, but not work so hard at it. So I try an orbital sander. Even though orbital sanders are mischeviously designed to sand across the grain no matter which way you point them. Usually I speed through the job, and sit back in satisfaction of the time saved. But then I inspect the surface. Swirls! Scratches! Even with the finest grits! Ugh! I renew my vow to never again use that cute little Mouse sander.

Last month my mother had a hardwood floor installed. By professionals. The layout and accenting was impeccable. It was truly magnificent. But then! In came the big vibrating sander to leave a bunch of circular markings behind! It is a stunning floor with a nice finish, but if you look closely you can see swirls and scratches.

Here's my dilemma. Professionals are using orbital sanders to finish fine hardwood floors. There are a gazillion models of finish sanders on the market, presumably to satisfy some sort of huge appetite for them. Why?! How?! Who is buying all this stuff? Are they making it work better than I am? Am I missing the Secret?

I am considering laying in a supply of those little 2.5 x 14 Porter Cable belt sanders, and using them as sanding blocks. These will not leave swirls in my masterpieces. It seems an expensive way to make my sanding jobs easier but I see no other choice if I want to avoid the swirls and scratches.

 

Don't have problem but I am building oak kitchen and finishing with 220 and 600 paper,

 

There are good orbitals and bad ones. The worst sander I have used was the Bosch. The best is the Festool 150/3. The air sanders also typically perform very well. If you want the speed of an orbital and swirl free, then you need to use both. Use an orbital to do most of the work and then with your final grit, sand with the orbital and then take out the swirls by hand with the same grit.

As far as flooring, it is not expected that you will get the same level of finishing with a floor as you would with cabinetry. You generally don't see it unless you are on your kness. I think they only sand to 100 grit anyway.

 

Never had the problems you describe, and I rarely use paper finer than 320. Works on pine, oak, maple, etc., etc. What I rarely use is my belt sander, it tears up wood horribly.

 

I'm like Bill; my DeWalt r.o.s. gets lots more work than the belt sander and I, too, generally finish sand with 320. I've never had an issue with the quality of the surface.

 

I've always seen swirl marks with orbitals. The better ones aren't as noticeable.

 

I watched our solid surface guy polish sections of the stuff, on our last commercial job, and his final was actually a pad in 600 grit. Wouldn't even scratch your fingernail, but it shined the solid surface nicely. I have a couple of the pads and will be trying them on my next sanding job to see if they leave swirls. Let you know.

 

The deep swirly marks you refer to usually come from a piece of grit coming off your pad, doesn't get sucked up into the vacuum holes, and it's made worse when the person using the sander puts too much pressure on the sander as they sand.

IMO there are a few things can help avoid the swirly marks.

First, don't use sanders that don't have vac holes in the paper. Also, pick the right grit of paper to begin with. If the surface is fairly smooth then there is no reason to start sanding with 60 or 80 grit. I use 120 in my orbital to sand out any milling marks left by the planer. Hold the sander lightly and let it do the work. NEVER EVER bear down on the sander. If you push on it at all you're more likely to have problems. If you think you need to bear down on the sander then in all likelihood you need to put on a new sanding disk. Also don't drop your sander off the workbench. Believe it or not, that's what causes many a good sander's demise- it gets dropped on the floor and you curse under your breath then continue to USE it, even though it's now probably got a nice wobble to it.

The other thing that leads to swirls is that the person using may have gotten impatient. He's sanded for 10 minutes using 80 grit, and by the time he switches to 120 grit he's tired of sanding and just wants to get done, so he sands for 5 minutes with 120, then switches to 180 grit and sands for 2 minutes. What i'm saying is that when you have swirls it might partly be because there wasn't enough time spent using the finer grits.

1/4 random orbit sheet sanders seem to leave WAY more scratches than the round orbitals. IMO, its because round orbitals have better suction.

I use a 5" Dewalt orbital all the time on the oak I finish, I use 120 and 150, and rarely if ever see any of the swirls anymore. (even though I used to) I've convinced myself that now I know what I'm doing. LOL

 

I own and use almost everyday 3, random orbital sands, A Porta Cable and two Ridgid brands, I'd be lucky is I use one of my two belt sanders twice a year. I only use Mirka brand sandpaper I found on Amazon.com. Cheaper and for some reason it almost never loads up like cheaper papers do.
We do anything from restore 100 year old houses, to restoring the bright work on boats. Every piece of wood trim we buy gets sanded to get out the mill marks before priming and sanding. Let the sander do the work, use a quality paper, hool it up to a vacuum and hold it flat and there will not be any swirl marks.

 

I have a DeWalt ros and I've seen the circular scratches. I see them whenever I'm in a hurry and unwilling to allow the sander to work as it was designed. Use and attached vacuum, use the correct grit paper, use the correct technique and you shouldn't have a problem.

 

Hmmmm, vacuum, you say. Quality tools, you say. Persist to a fine grit, you say. Use good technique, you say. These things, although foreign to me, may make some sense. Thanks for the input, I will take your advice before collecting 12 tiny belt sanders.